[Federal Register: September 30, 2010 (Volume 75, Number 189)]
[Proposed Rules]
[Page 60515-60561]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr30se10-27]
[[Page 60515]]
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Part II
Department of the Interior
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Fish and Wildlife Service
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50 CFR Part 17
Endangered and Threatened Wildlife and Plants; 12-Month Finding on a
Petition to List the Pygmy Rabbit as Endangered or Threatened; Proposed
Rule
[[Page 60516]]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R8-ES-2007-0022]
[MO 92210-0-0008-B2]
Endangered and Threatened Wildlife and Plants; 12-Month Finding
on a Petition to List the Pygmy Rabbit as Endangered or Threatened
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of a 12-month petition finding.
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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a
12-month finding on a petition to list the pygmy rabbit (Brachylagus
idahoensis) as endangered or threatened under the Endangered Species
Act of 1973, as amended. After review of all available scientific and
commercial information, we find the listing of the pygmy rabbit is not
warranted at this time. However, we ask the public to submit to us any
new information that becomes available concerning the threats to the
pygmy rabbit or its habitat at any time.
DATES: The finding announced in the document was made on September 30,
2010.
ADDRESSES: This finding is available on the Internet at http://
www.regulations.gov at Docket Number FWS-R8-ES-2007-0022. Supporting
documentation we used to prepare this finding is available for public
inspection, by appointment, during normal business hours at the U.S.
Fish and Wildlife Service, 1340 Financial Boulevard, Suite 234, Reno,
NV 89502. Please submit any new information, materials, comments, or
questions concerning this species to the Service at the above street
address.
FOR FURTHER INFORMATION CONTACT: Robert D. Williams, State Supervisor,
U.S. Fish and Wildlife Service, Nevada Fish and Wildlife Office (see
ADDRESSES); by telephone (775) 861-6300 or by facsimile (775) 861-6301.
Persons who use a telecommunications device for the deaf (TDD) may call
the Federal Information Relay Service (FIRS) at (800) 877-8339.
SUPPLEMENTARY INFORMATION:
Background
Section 4(b)(3)(B) of the Endangered Species Act of 1973, as
amended (Act) (16 U.S.C. 1531 et seq.), requires that, for any petition
to revise the List of Endangered and Threatened Wildlife and Plants
that contains substantial scientific or commercial information that the
listing may be warranted, we make a finding within 12 months of the
date of the receipt of the petition. In this finding, we will determine
that the petitioned action is either: (1) Not warranted, (2) warranted,
or (3) warranted, but the immediate proposal of a regulation
implementing the petitioned action is precluded by other pending
proposals to determine whether species are endangered or threatened ,
and expeditious progress is being made to add or remove qualified
species from the Lists of Endangered and Threatened Wildlife and
Plants. Section 4(b)(3)(C) of the Act requires that we treat a petition
for which the requested action is found to be warranted but precluded
as though resubmitted on the date of such finding; that is, requiring a
subsequent finding to be made within 12 months. We must publish these
12-month findings in the Federal Register.
Previous Federal Actions
On November 21, 1991, we added the pygmy rabbit to our list of
candidate species as a category 2 candidate species (56 FR 58804). A
category 2 candidate species was a species for which we had information
indicating that a proposal to list it as threatened or endangered under
the Act may be appropriate, but for which additional information on
biological vulnerability and threat was needed to support the
preparation of a proposed rule. In the February 28, 1996, Candidate
Notice of Review (CNOR) (61 FR 7595), we adopted a single category of
candidate species defined as follows: ``Those species for which the
Service has on file sufficient information on biological vulnerability
and threat(s) to support issuance of a proposed rule to list but
issuance of the proposed rule is precluded.'' In previous CNORs,
species matching this definition were known as category 1 candidates
for listing. Thus, the Service no longer considered category 2 species
as candidates and did not include them in the 1996 or any subsequent
CNORs. The decision to stop considering category 2 species as
candidates was designed to reduce confusion about the status of these
species and to clarify that we no longer regarded these species as
candidates for listing.
On April 21, 2003, we received a petition dated April 1, 2003, from
the Committee for the High Desert, Western Watersheds Project, American
Lands Alliance, Oregon Natural Desert Association, Biodiversity
Conservation Alliance, Center for Native Ecosystems, and Mr. Craig
Criddle requesting the pygmy rabbit found in Oregon, Idaho, Montana,
Wyoming, California, Nevada, and Utah be listed as endangered or
threatened in accordance with section 4 of the Act (Committee for the
High Desert et al. 2003, entirety). The petition was clearly identified
as a petition and contained the names, signatures, and addresses of the
requesting parties. The petitioners requested designation of critical
habitat concurrent with the listing. Included in the petition was
supporting information regarding the species' taxonomy and ecology,
historical and current distribution, and perceived threats to the pygmy
rabbit.
On June 10, 2003, we acknowledged in a letter the receipt of the
petition and stated we determined an emergency listing was not
warranted for the pygmy rabbit. We also stated if our ongoing status
review of the species indicates that an emergency listing is warranted,
we would act accordingly. In addition, we advised the petitioners that
we would not be able to process the petition in a timely manner. On May
3, 2004, we received a 60-day notice of intent to sue, and on September
1, 2004, we received a complaint regarding our failure to carry out the
90-day and 12-month findings on the status of the pygmy rabbit. On
March 2, 2005, we reached an agreement with the plaintiffs to submit to
the Federal Register a completed 90-day finding by May 16, 2005, and to
complete, if applicable, a 12-month finding by February 15, 2006
(Western Watersheds Project et al. v. U.S. Fish and Wildlife Service
(CV-04-0440-N-BLW) (D. Idaho).
On May 20, 2005, we published a 90-day finding in the Federal
Register (70 FR 29253) stating that the petition did not present
substantial information indicating that listing the pygmy rabbit may be
warranted. On March 28, 2006, we received a complaint regarding alleged
violations of the Act and the Administrative Procedure Act with regard
to our May 20, 2005, 90-day finding (Western Watersheds Project et al.
v. Gale Norton and U.S. Fish and Wildlife Service (CV 06-CV-00127-S-
EJL) (D. Idaho)). On September 26, 2007, the court issued an order
remanding our May 20, 2005, 90-day finding and required the Service to
issue a new 90-day finding on or before December 26, 2007. On January
8, 2008, we published a new 90-day finding (73 FR 1312), and determined
that the petition presented substantial information indicating that the
petitioned action may be warranted. Additionally in that notice, we
indicated that we would be initiating a status review of the pygmy
rabbit and opening a 60-day public comment period.
[[Page 60517]]
This finding does not address our prior listing of the Columbia
Basin distinct population segment (DPS) of the pygmy rabbit which
occurs in the State of Washington. On November 30, 2001, we published
an emergency listing and concurrent proposed rule to list this DPS of
the pygmy rabbit as endangered (66 FR 59734 and 66 FR 59769,
respectively). We listed the Columbia Basin DPS of the pygmy rabbit as
endangered in our final rule dated March 5, 2003 (68 FR 10388). This
finding addresses the petitioned action that requests listing of the
pygmy rabbit as endangered or threatened in the remainder of its range
in Oregon, Idaho, Montana, Wyoming, California, Nevada, and Utah.
Species Information
Species Description
The pygmy rabbit is the smallest North American Leporid. Adult
weights range from 0.54 to 1.2 pounds (245 to 553 grams); adult lengths
range from 9.1 to 12.1 inches (in) (23.1 to 30.7 centimeters (cm))
(Dice 1926, p. 28; Grinnell et al. 1930, p. 554; Bailey 1936, p. 110;
Orr 1940, p. 194; Janson 1946, pp. 21, 23; Durrant 1952, p. 88; Ingles
1965, p. 143; Bradfield 1974, pp. 10-11; Holt 1975, pp. 125-126;
Campbell et al. 1982, p. 100). Adult females are generally larger than
adult males. The species can be distinguished from other rabbits by its
small size, gray color, short rounded ears, small hind legs, and the
absence of white on the tail (66 FR 59734).
Taxonomy
The pygmy rabbit is a member of the family Leporidae, which
includes rabbits and hares. This species has been placed in various
genera positions since its type specimen was described in 1891 by
Merriam (1891, pp. 76-78), who classified the ``Idaho pygmy rabbit'' as
Lepus idahoensis. Currently, the pygmy rabbit is generally placed
within the monotypic genus Brachylagus and classified as B. idahoensis
(Green and Flinders 1980a, p. 1; Washington Department of Fish and
Wildlife (WDFW) 1995, p. 1); this is the taxonomy accepted by the
Service. The analysis of blood proteins (Johnson 1968, cited in WDFW
1995, p. 1) suggests that the pygmy rabbit differs greatly from species
within both the Lepus and Sylvilagus genera. Halanych and Robinson
(1997, p. 301) supported the separate generic status as Brachylagus for
the pygmy rabbit based on phylogenetic position and sequence divergence
values. The pygmy rabbit has no recognized subspecies (Grinnell et al.
1930, p. 555; Davis 1939, p. 364; Larrison 1967, p. 64; Green and
Flinders 1980a, p. 1; Janson 2002, p. 4).
Ecology and Life History
Pygmy rabbits are typically found in areas of tall, dense Artemisia
spp. (sagebrush) cover and are considered a sagebrush obligate species
because they are highly dependent on sagebrush to provide both food and
shelter throughout the year (Dice 1926, p. 27; Grinnell et al. 1930, p.
553; Orr 1940, pp. 194-197; Hall 1946, p. 615; Janson 1946, pp. 39-40,
53; Wilde 1978, p. 46; Green and Flinders 1980a, pp. 1-3 and b, pp.
137-141; Weiss and Verts 1984, pp. 569-570; Katzner et al. 1997, p.
1,053). Anthony (1913, p. 22) also mentioned he found pygmy rabbits in
``little draws and flats'' in Oregon, where the tall sagebrush was
thick and where Chrysothamnus spp. (rabbit brush) grew in extensive
patches, and occasionally they were found on ``sparsely brushed flats
and hills.''
The winter diet of pygmy rabbits is composed of up to 99 percent
sagebrush (Wilde 1978, p. 46; Green and Flinders 1980b, p. 138), which
is unique among leporids (rabbits and hares) (White et al. 1982, p.
107). During spring and summer in Idaho, their diet consists of
approximately 51 percent sagebrush, 39 percent grasses (particularly
native bunch-grasses, such as Agropyron spp. and Poa spp.), and 10
percent forbs (Green and Flinders 1980b, p. 138). There is evidence
that pygmy rabbits preferentially select native grasses as forage over
other available foods during this period. In addition, total grass
cover relative to forbs and shrubs may be reduced within the immediate
areas occupied by pygmy rabbits as a result of their use during spring
and summer (Green and Flinders 1980b, pp. 138-141). The specific diets
of pygmy rabbit likely vary by region (68 FR 10388).
Pygmy rabbits may be active at any time of the day or night, and
appear to be most active during mid-morning (Anthony 1913, p. 23;
Bailey 1936, p. 111; Bradfield 1974, pp. 14-15; Green and
Flinders1980a, p. 3; Gahr 1993, pp. 45-46). Flinders et al. (2005, p.
27) found pygmy rabbits to be 72 percent more active during twilight.
Larrucea (2007, p. 79) found pygmy rabbits were most active during dawn
and dusk (a bimodal diel activity pattern). Activity at dawn was
greatest except for during winter when dusk activity was higher. Lee
(2008, p. 33) found pygmy rabbits were active during all time periods
of the day, but the greatest activity occurred at night.
Pygmy rabbits maintain a low stance, have a deliberate gait, and
are relatively slow and vulnerable in more open areas. They can evade
predators by maneuvering through the dense shrub cover of their
preferred habitats, often along established trails, or by escaping
among their burrows (Anthony 1913, pp. 22-23; Bailey 1936, p. 111;
Severaid 1950, p. 3; Bradfield 1974, pp. 26-27). Due to their small
size, behavior, and habitat, these small rabbits can be easily
overlooked (Merriam 1891, p. 75; Grinnell et al. 1930, p. 553; Janson
1940, p. 1; Severaid 1950, p. 3; Holt 1975, p. 135; Janson 2003, p.
71).
The pygmy rabbit is one of only two rabbits in North America that
digs its own burrows (Nelson 1909, p. 22; Bailey 1936, p. 111; Hall
1946, p. 617; Janson 1946, p. 43; Bradfield 1974, p. 28; Wilde 1978, p.
17). Pygmy rabbit burrows are typically found in relatively deep, loose
soils of wind-borne or water-borne (e.g., alluvial fan) origin. Pygmy
rabbits, especially juveniles, likely use their burrows as protection
from predators and inclement weather (Bailey 1936, p. 111; Bradfield
1974, pp. 26-27). Some burrows have only one entrance. Others have
multiple entrances, some of which are concealed at the base of larger
sagebrush plants (Dice 1926, p. 27). A single entrance burrow may be
referred to as a ``burrow'' while single entrance burrows, multi-
entrance burrows, or an entire site may be referred to as a ``burrow
system''. Burrows are relatively simple and shallow, often no more than
2.2 yards (yd) (2 meters (m)) in length and usually less than 1.1 yd (1
m) deep with no distinct chambers (Bailey 1936, p. 111; Bradfield 1974,
pp. 29-30; Green and Flinders 1980a, p. 2; Gahr 1993, p. 63). Burrows
are typically dug into gentle slopes or mound or inter-mound areas of
more level or dissected topography (Wilde 1978, p. 26; Gahr 1993, pp.
77-80).
In general, the number of active burrows in an area increases over
the summer as the number of juveniles increase. However, the number of
active burrows may not be directly related to the number of individuals
in a given area because some individual pygmy rabbits appear to
maintain multiple burrows and some individual burrows are used by
multiple individuals (Janson 1940, p. 21; Janson 1946, p. 44; Gahr
1993, pp. 66, 68; Heady 1998, p. 25).
Pygmy rabbits may also be using more than one burrow or burrow
system at a specific time or during different times of the year
(Purcell 2006, p. 96). In Idaho, Sanchez and Rachlow (2008, p. 1306)
found the number of burrows used by individuals increased with home
range size. Patterns of burrow system use varied by study area, sex,
and season (Sanchez and Rachlow 2008, pp. 1306-
[[Page 60518]]
1307). Larrucea (2007, pp. 96-97) found annual and intra-annual changes
at three study sites during a 3-year period in the Reese River Valley,
Nevada. During two of the three years, one site showed lack of activity
during winter and spring. Pygmy rabbits returned to this site in June
and many new burrows were found. This site may have been marginal
habitat and rabbits using the area in June may have been dispersing
juveniles from other areas. At the other two sites where pygmy rabbits
were observed year-round, the fewest active burrows were found from
July to October. With the return of cooler weather in the fall, the
number of active burrows again increased. Many of these new active
burrows were ones that had previously been inactive or collapsed.
Flinders et al. (2005, p. 25) reported distances between burrow
systems. They found burrow systems with multiple entrances averaged
124.6 yd (114.0 m) away from the next nearest multiple entrance system,
while distances between systems with multiple entrances to single
entrance burrows averaged 57.1 yd (52.2 m) away. Single entrance burrow
systems averaged 14 yd (12.8 m) away from the nearest single entrance
system.
Pygmy rabbits occasionally make use of burrows abandoned by other
species, such as the yellow-bellied marmot (Marmota flaviventris),
badger (Taxida taxus), or Utah prairie dog (Cynomys parvidens) (Borell
and Ellis 1934, p. 41; Hall 1946, p. 617; Bradfield 1974, p. 28; Green
and Flinders 1980a, p. 2; Flinders et al. 2005, p. 30). As a result,
they may occur in areas of shallower or more compact soils that support
sufficient shrub cover (Bradfield 1974, p. 29). Natural cavities (such
as holes in volcanic rock), rock piles, stone walls, and areas around
abandoned buildings may also be used (Janson 1946, pp. 44-46). During
winter, pygmy rabbits make extensive use of snow burrows, possibly for
access to sagebrush forage (Bradfield 1974, p. 17; Katzner and Parker
1997, p. 1,069), as travel corridors among their underground burrows,
for protection from predators, and/or as thermal cover (Katzner and
Parker 1997, pp. 1,063, 1,069-1,070).
Pygmy rabbits tend to have relatively small home ranges during
winter, remaining within 98 ft (30 m) of their burrows (Janson 1946, p.
75). Bradfield (1974, p. 20), Katzner and Parker (1997, p. 1,066), and
Flath and Rauscher (1995, p. 3) found pygmy rabbit tracks in snow
indicating movements of 262 to 328 ft (80 to 100 m) or more from their
burrows. They have larger home ranges during spring and summer (Janson
1946, p. 75; Gahr 1993, pp. 103-105). During the breeding season in
Washington, females tend to make relatively short movements within a
small core area and have home ranges covering roughly 6.7 acres (ac)
(2.7 hectares (ha)); males tend to make longer movements, traveling
among a number of females, resulting in home ranges covering roughly
49.9 ac (20.2 ha) (Gahr 1993, p. 118). Katzner (1994, pp. 14-15) found
home range size extremely variable in Wyoming; home ranges were from
0.12 to 0.86 ac (0.05 to 0.35 ha) for females and 0.82 to 4.4 ac (0.33
to 1.8 ha) for males. Burak (2006, p. 22) found in Owyhee County,
Idaho, that pygmy rabbit home range sizes based on Minimum Convex
Polygons differed between the sexes and ranged from 49.9 to 69.7 ac
(20.2 to 28.2 ha) for males and from 4 to 5.4 ac (1.6 to 2.2 ha) for
females during the breeding season. Crawford (2008, p. 47) found that
pygmy rabbit annual home ranges in southeastern Oregon and northwestern
Nevada differed between the sexes and ranged from 1.2 to 25.8 ac (0.49
to 10.46 ha) for males and 0.27 to 18.7 ac (0.11 to 7.55 ha) for
females. During the breeding season, home ranges for males ranged from
0.27 to 18.5 ac (0.11 to 7.49 ha) and from 0.15 to 17.5 ac (0.06 to
7.10 ha) for females.
Sanchez and Rachlow (2008, p. 1307) in Idaho found range use
between consecutive seasons and between seasons over 2 years was highly
variable; some pygmy rabbits shifted seasonal ranges markedly, but most
ranges showed overlap between seasons and years. One male shifted his
range center by 8,013.9 yd (7,332 m), but other males shifted their
range centers between 33 and 122 yd (30 and 112 m). Females shifted
their range centers between 58 and 144 yd (53 and 132 m) (Sanchez and
Rachlow 2008, p. 1307). Distances shifted between like seasons over the
2 years were similar to those observed between consecutive seasons.
Males showed a distance shift of between 47 and 269 yd (43 and 246 m)
and females showed a shift of between 0 and 150 yd (0 and 137 m)
(Sanchez and Rachlow 2008, p. 1307).
Earlier reports indicated pygmy rabbits were known to have traveled
up to 0.75 mile (mi) (1.2 kilometers (km)) from their burrows (Gahr
1993, p. 108), and there are a few records of individuals moving up to
2.17 mi (3.5 km) (Green and Flinders 1979, p. 88; Katzner and Parker
1998, p. 73). Rauscher (1997, p. 5) reported that pygmy rabbits crossed
500 yd (457.2 m) of relatively open grassland habitat to reach a
sagebrush stringer in Montana. Katzner (1994, p. 105) accounted for all
the rabbits within a range of 0.62 mi (1 km) of his study area. When
pygmy rabbits not previously observed appeared, he concluded these
individuals must have traveled a ``considerable distance.'' More
recently, Estes-Zumpf and Rachlow (2009, p. 367) radio-tagged juvenile
pygmy rabbits in Idaho and found median dispersal movements of 0.93 mi
(1.5 km) and 3.9 mi (6.2 km) and maximum dispersal movements of 4.0 mi
(6.5 km) and 7.4 mi (11.9 km) by male and female rabbits, respectively.
Burak (2006, p. 27) indicated the maximum distance a male pygmy rabbit
moved was 1,662.5 yd (1,521 m) and 1,112.7 yd (1,018 m) for a female.
Crawford (2008, p. 54) in Nevada and Oregon reported that 24 radio-
marked rabbits moved greater than 0.3 mi (0.5 km) with a maximum long-
distance movement of 5.3 mi (8.5 km) recorded by a juvenile female.
Twenty-one of the individuals that traveled greater than 0.3 mi (0.5
km) were juveniles.
Pygmy rabbits may begin breeding the year following their birth
(Wilde 1978, pp. 64-66, 127; Fisher 1979, p. 13). In some parts of the
species' range, females may have up to three litters per year and
average six young per litter (Davis 1939, p. 365; Hall 1946, p. 618;
Janson 1946, pp. 67-69; Green 1978, pp. 35-36; Wilde 1978, p. 69).
Breeding appears to be highly synchronous in a given area and juveniles
are often identifiable to cohorts (Wilde 1978, pp. 69-70). Prior to
publication of a study in 2005, no evidence of nests, nesting material,
or lactating females with young had been found in burrows (Bailey 1936,
p. 111; Janson 1940, p. 23; Janson 1946, p. 69; Bradfield 1974, p. 29;
Gahr 1993, p. 82 Rauscher 1997, p. 11). Recent studies have found that
natal burrows are constructed by pygmy rabbits. Rachlow et al. (2005,
pp. 137-138) provide information on seven natal burrows found in Lemhi
Valley, Idaho. Females were observed digging and subsequently back-
filling burrows with soil. Fine grasses, shredded sagebrush bark, and
hair were the primary components used in the nesting material. Larrucea
(2007, pp. 89-90) found three natal burrows in Reese River Valley,
Nevada, but did not describe them. Burak (2006, p. 29) found female
pygmy rabbits construct natal burrows outside of their original home
range core area. Three of the four natal burrows he found were located
outside of the core area; the fourth female stayed within a second core
area that included the natal burrow and when the burrow became
inactive, she returned to her original core area (Burak 2006, p. 29).
Individual juveniles have been found under clumps of sagebrush,
although it is not known if they are
[[Page 60519]]
routinely hidden at the bases of scattered shrubs or within burrows
(Wilde 1978, p. 115).
A wide range of pygmy rabbit population densities has been
reported. Janson (1946, p. 84) reported estimated pygmy rabbit
densities of 0.75 to 1.75 per ac (1.9 to 4.3 per ha) and 3.5 pygmy
rabbits per ac (8.6 per ha) in Utah. Flinders et al. (2005, p. 16)
reported 0.3 rabbits per ac (0.79 rabbits per ha) in Grass Valley,
Utah. Green (1978, p. 62) reported an estimate of 18.2 pygmy rabbits
per ac (45 per ha) in Idaho. In Montana, Rauscher (1997, p. 10)
estimated pygmy rabbit density as 0.67 rabbits per burrow or 1.2 per ac
(3.0 per ha). Based on fecal dropping counts, Larsen et al. (2006, pp.
26-27) estimated rabbit density in Deep Creek watershed, Utah, as 0.07
per ac (0.17 rabbits per ha). Using line transects in Wyoming, Purcell
(2006, pp. 100, 105) reported a range of burrow systems per mi (km) for
systematic transects (1.7 to 18.2 per mi, 2.7 to 29.3 per km) and
random transects (0.8 to 7.4 per mi, 1.33 to 11.97 per km) in 10 study
areas. Larrucea (2007, p. 89) estimated, using transect counts, that
the relative density at five study areas in California and Nevada
ranged from 0.4 to 1.7 rabbits per ac (0.9 to 4.2 rabbits per ha).
The annual mortality rate of adult pygmy rabbits may be as high as
88 percent, and more than 50 percent of juveniles can die within
roughly 5 weeks of their emergence (Wilde 1978, pp. 139-140). Estes-
Zumpf and Rachlow (2009, p. 367) found mortality rates were 69.2
percent and 88.5 percent for male and female juvenile pygmy rabbits,
respectively, in their study area in east-central Idaho. The mortality
rate was highest within two months of emerging from the natal burrow.
However, the mortality rates of adult and juvenile pygmy rabbits can
vary considerably between years, and even between juvenile cohorts
within years (Wilde 1978, pp. 85-95, 138-140). Predation is the main
cause of pygmy rabbit mortality (Green 1979, p. 25). Sanchez (2007, pp.
90-91) attributed 42 percent of natural mortalities to mammalian and
avian predation. She was unable to determine the cause of death in 58
percent of the mortalities.
Predators of the pygmy rabbit include badgers, long-tailed weasels
(Mustela frenata), coyotes (Canis latrans), bobcats (Felis rufus),
great horned owls (Bubo virginianus), long-eared owls (Asio otus),
ferruginous hawks (Buteo regalis), northern harriers (Circus cyaneus),
and common ravens (Corvus corax) (Borell and Ellis 1934, p. 42; Janson
1946, pp. 89-90; Gashwiler et al. 1960, p. 227; Green 1978, p. 37;
Wilde 1978, pp. 96, 141-143; Johnson and Hanson 1979, p. 952; WDFW
1995, p. 6).
Sanchez (2007, p. 92) estimated that for known-aged rabbits, the
average lifespan was 1.16 years. For rabbits captured as adults,
assuming a birth date of May 1 of the previous year, estimated average
life expectancy was 1.7 years, and the maximum lifespan achieved was
3.3 years.
Population cycles are not known in pygmy rabbits, although local,
relatively rapid population declines have been noted in some States
(Janson 1946, p. 84; Bradfield 1974, p. 39; Weiss and Verts 1984, p.
569). Janson (2003, p. 71) remarked that pygmy rabbits likely undergo
local, if not regional, fluctuations. After initial declines, pygmy
rabbit populations may not have the same capacity for rapid increases
in numbers in response to favorable environmental conditions as
compared to other rabbit species. This may be due to their close
association with specific components of sagebrush ecosystems, and the
relatively limited availability of their preferred habitats (Wilde
1978, p. 145; Green and Flinders 1980b, p. 141; WDFW 1995, p. 13). No
study has documented rapid increases in pygmy rabbit numbers in
response to environmental conditions (Gabler 1997, p. 95). Long-term
population monitoring studies are not available indicating whether
population fluctuations or cycles occur for pygmy rabbits or if
seasonal or other habitat shifts or movements have been misinterpreted
as declines.
Literature indicates that pygmy rabbits have never been evenly
distributed across their range (Bailey 1936, p. 111; Janson 1940 p. 5;
Holt 1975, pp. 133-134). While the species occurs throughout most of
the Great Basin, they exhibit extremely specialized habitat
requirements, and thus occupy only a small subset of locations within
this range (Larrucea 2007, p. 2). They are found in areas within their
broader distribution where sagebrush cover is sufficiently tall and
dense, and where soils are sufficiently deep and loose to allow
burrowing (Bailey 1936, p. 111; Green and Flinders 1980a, p. 2;
Campbell et al. 1982, p. 100; Weiss and Verts 1984, p. 563; WDFW 1995,
p. 15). Sagebrush- dominated communities are naturally subject to
disturbances of various kinds resulting in a heterogeneous distribution
of different stand sizes and age classes, and on the landscape scale,
pygmy rabbit distribution is naturally disjunct (Himes and Drohan 2007,
p. 380). Local distribution of this habitat and thus pygmy rabbit
populations likely shift over time due to natural and human
disturbances including fire, agriculture production, flooding, grazing,
and weather patterns (Keinath and McGee 2004, p. 5). In the past, dense
vegetation along permanent and intermittent stream corridors, alluvial
fans, and sagebrush plains probably provided travel corridors and
dispersal habitat for pygmy rabbits between suitable use areas (Green
and Flinders 1980a, p. 1; Weiss and Verts 1984, p. 570; WDFW 1995, p.
15). Since European settlement of the western United States, dense
vegetation associated with human activities (fence rows, roadway
shoulders, borrow ditches, crop margins, abandoned fields) may have
also acted as avenues of dispersal between local populations of pygmy
rabbits (Green and Flinders 1980a, p. 1; Rauscher 1997, p. 16).
Distribution, Abundance, and Trends
The pygmy rabbit's general historical and current geographic range,
excluding the Columbia Basin DPS, includes most of the Great Basin and
some of the adjacent intermountain areas of the western United States
(Green and Flinders 1980a, p. 1), and the boundaries can be described
as follows: the northern boundary extends into southeastern Oregon and
southern Idaho. The eastern boundary extends into southwestern Montana
and south central Wyoming. The southeastern boundary extends into
southwestern Utah. Central Nevada and eastern California provide the
southern and western boundaries (Merriam 1891, p. 75; Nelson 1909, p.
275; Grinnell et al. 1930, pp. 553, 558; Bailey 1936, pp. 110-111;
Janson 1946, pp. 32-33; Campbell et al. 1982, p. 100; WDFW 1995, pp. 1-
2, Purcell 2006, pp. 1, 7-11, 30). Based on available information, the
current distribution of the pygmy rabbit indicates a possible range
contraction in northern California (Larrucea and Brussard 2008a, p.
696). Because uncertainty remains about whether this possible range
contraction has occurred due to limited survey efforts in northern
California both historically and recently, it is not shown in Figure 1.
Figure 1 illustrates the approximate historical and current range of
the pygmy rabbit in the seven States discussed in this finding.
[[Page 60520]]
[GRAPHIC] [TIFF OMITTED] TP30SE10.008
Figure 1. Approximate historical and current range (based on data
from 1877 to 2008) of the pygmy rabbit (Brachylagus idahoensis) not
including the Columbia Basin DPS in Washington State.
To determine the historical and current distribution and trend
analysis for pygmy rabbits across the seven States discussed in this
finding, we reviewed published scientific peer-reviewed literature;
unpublished agency documents; dissertations; theses; databases
maintained by State heritage programs, State wildlife agencies, and
Federal agencies; survey data sheets; museum records; electronic mail
records; and agency notes to the files. Older published literature
(prior to the mid to late 1990's) generally focused on the species'
life history, behavior, and some habitat relationships and provided
location information of study areas. More recent unpublished literature
(since the mid to late 1990's to 2008) has been primarily related to
surveys conducted by government agencies or their consultants and
universities to determine pygmy rabbit occurrence within portions of a
State and some information regarding species' life history, behavior,
and habitat relationships. Survey efforts have focused on location of
pygmy rabbit signs rather than on documenting known or perceived
threats to the species at these sites. Rarely has revisiting of sites
occurred with the purpose of monitoring populations over time. While we
consider this information of limited use to our finding due to its
local, short-term nature, it is the best scientific information
available to conduct our analysis.
We compiled a database of records (location points) of various
pygmy rabbit signs for each State from these various data sources
listed above. Some records were not entered into a State database if
adequate information was
[[Page 60521]]
not provided (e.g., we could not determine a location point because the
source map did not indicate location or survey data sheet location
point information was unreadable). Once each State database was
compiled, we reviewed each location point and eliminated its database
record if it was not determined to be a reliable data point as
discussed below. The final databases combined contain approximately 68
percent of all the location points compiled. We consider the location
point data retained in these seven State databases to be the best
scientific information available. We will refer to these created State
databases as the Service's databases.
We are aware of concerns related to the use of anecdotal occurrence
records to determine distribution of species (McKelvey et al. 2008, pp.
549-554). We are also aware of confidence levels related specifically
to pygmy rabbit presence and level of activity at particular sites due
to various factors (e.g., sighting of targeted species vs. only
targeted species sign or potential targeted species sign observed; if
burrow activity is uncertain, the site should be revisited;
uncertainties due to other species or other rabbit species using
burrows; pellets being misidentified) (Bartels 2003, pp. 47-49; Keinath
and McGee 2004, pp. 32-34).
As a result of these concerns, we have based our analysis on what
we considered to be the more reliable records indicating pygmy rabbit
presence and activity level. The following types of records were not
included in the Service's databases for our analysis: database records
that showed some level of uncertainty for the information being
provided (e.g., other leporid species data included; uncertainty about
whether pygmy rabbit was observed or other leporid species; using words
such as ``possible'', ``potential'', ``maybe'', ``unsure''); records
that only provided location data or indicated pygmy rabbit sign with no
additional information indicating what type of sign (e.g., burrow,
pellet, track, sighting of animal as relates to reliability) had been
observed; records related to telemetry locations (while informative in
determining an individual's distribution within its home range, this
provides little information at the larger landscape scale used here; we
did include the capture location of any individual pygmy rabbit trapped
and fitted with a tradio collar); records based solely on pellets or
tracks due to concerns with species misidentification; those lacking
key information (e.g., year which is needed for trend analysis) and
duplicate records.
For our analysis, we mapped records of ``active'' sites or burrows
defined as those database records that indicated an activity level (at
the time of the survey) of current, present, occupied, active, or
recently active burrows; burrows in combination with fresh pellets; a
visual sighting; photographic evidence; fecal DNA confirmation;
specimen collected; trapping effort; in combination with tracks; or any
combination thereof. All sighting records were included in our analysis
even if no other information was provided, unless uncertainty was
expressed about whether it had been a pygmy rabbit observed or another
leporid species.
We also mapped records of ``inactive'' sites or burrows defined as
those database records that indicated an activity level (at the time of
the survey) of inactive, not recent, old, very old, collapsed, or
burrow plus old pellets. In addition, we assumed ``inactive'' for site
or burrow records that did not provide a status and did not provide
information to support a determination of active, those with an
``undetermined'' activity status, or were unclear. We reviewed the
mapped distribution for the ``active'' and ``inactive'' site categories
across each State.
In addition, we mapped database records of ``absent'' areas defined
as points where no sign of pygmy rabbit occupancy was evident. Most
databases do not include records of areas surveyed but where no pygmy
rabbit sign was observed. We believe this type of information can be
valuable; however, we do not assume that pygmy rabbits were or should
have been present in areas where they were determined to be absent. It
is possible that an area is unsuitable for pygmy rabbits while
appearing suitable to surveyors. Conversely, it is possible an area
that appears unsuitable to surveyors for pygmy rabbits may actually be
so (Ulmschneider et al. 2004, pp. 2-3). On the ground surveying is
necessary to positively indicate pygmy rabbit occupancy (Bartels 2003,
pp. 92-94; Lenard et al. 2005, p. 1; Meisel 2006, pp. 26, 48). The
``absent'' information indicates locations where survey efforts were
conducted but pygmy rabbit sign was not evident. Limited ``absent''
information was obtained for the States of Oregon, California, Nevada,
and Wyoming.
During our analysis we encountered some difficulties in adapting
data collected for another's purpose for our species' status review,
and there were several limitations. Overall, survey information
collected over the years reflects different surveyors, different survey
methods, different levels of survey intensity, and different amounts
and types of information recorded. We generally accepted the
information indicated in a report, data sheet, or database and tried to
do as little interpretation as possible. For some locations, we
replaced locational descriptions (Township, Range and Section or a
narrative description) with Universal Transverse Mercator (UTM)
coordinates or a center point for a section surveyed or a point was
buffered to indicate an approximate location. For a portion of records
from Oregon, we created a point representing the center of a study area
and ``active'' and ``inactive'' burrows were separated.
We encountered some difficulties with interpreting data provided
under different reporting techniques. In general, most surveys for
pygmy rabbits report location information in terms of point data (i.e.,
legal description or Global Positioning System (GPS)) with qualifiers
or descriptions for sign, such as burrows (present, absent), activity
level (occupied, unoccupied, active, inactive, current, recent, old,
very old), pellets (fresh, old), sightings (actual sightings of pygmy
rabbits, specimen collection, capture, photographic record), and
tracks. Some surveyors developed their own rating system or confidence
level for burrow or site activity (Purcell 2006, p. 38; Himes and
Drohan 2007, p. 375; Flinders et al. 2005, pp. 8-9). Some efforts
reported only those sites that were considered positive (confirmed with
photographic evidence), active, or occupied sites and did not include
information for areas considered inactive or unoccupied. Location data
may represent a burrow, a burrow system, or an entire site that was
surveyed which represents one or more burrows or burrow systems.
Various techniques have been used to detect pygmy rabbit evidence
on the landscape. Techniques may include driving and walking transects
in perceived suitable habitat, winter aerial flights over potential
habitat with subsequent selection of areas for further ground surveys
(Rachlow and Witham 2006, pp. 4-8), random searches in perceived
suitable habitat, or spot lighting at night. Survey efforts have been
made during all times of the year. It is advised that sites that
indicate pygmy rabbit sign should be confirmed through sightings or
photographic evidence; this may or may not have occurred. The Service
has recommended using draft survey guidelines developed by Ulmschneider
et al. (2004, entire) in conducting
[[Page 60522]]
pygmy rabbit surveys, but it has not always been used since its
availability.
Larrucea (2007, p. 3) tested pellet, sighting, burrow, and camera
survey methods at 20 locations in 4 known, active pygmy rabbit
populations in California and Nevada. She also assessed road transect
surveys for detecting and determining relative abundance in an area
(Larrucea 2007, p. 3). Results indicated that pellets were found at all
sites, but pellets determined to be fresh were found at only 70 percent
of the sites. Sighting individual rabbits provided positive results 30
percent of the time. Burrows were located at 85 percent of the sites,
but burrows determined to be active were found at only 55 percent of
the sites. Cameras provided positive results 95 percent of the time
(Larrucea 2007, p. 6). Photographs were taken of pygmy rabbits at all
types of active sites including those with only burrows determined to
be inactive and with pellets determined to be old (Larrucea 2007, p.
7). During the 10 transect counts, different rabbit and hare species
were observed 569 times and 545 were identified to genus (Larrucea
2007, p. 7). Lepus was observed 491 times (90.1 percent); Sylvilagus 44
times (8.1 percent) and Brachylagus 10 times (1.8 percent) (Larrucea
2007, p. 7). Photographs taken from the camera locations provided 409
photos of rabbit and hare species; the number of photographs of Lepus
was 199 (48.7 percent), Brachylagus 195 (47.7 percent), and Sylvilagus
15 (3.7 percent) (Larrucea 2007, p. 7).
Camera surveys are more effective than burrow, pellet, sightings,
or road transect surveys for determining current pygmy rabbit activity
at a site (Larrucea 2007, p. 7). Burrows are a good indicator that
pygmy rabbits may be present, but locating one does not mean pygmy
rabbits are currently using the site (Larrucea 2007, p. 8). Lack of
active burrows may not mean that there are no pygmy rabbits in the
area. Burrows may be used seasonally, may be difficult to locate, or
may be lacking in dispersal areas (Larrucea 2007, pp. 8-9). Old pellets
do not confirm current use of a site and pellets may be misidentified
due to young rabbits of other species cohabiting a site. Not finding
fresh pellets does not mean pygmy rabbits are not currently using a
site as environmental conditions can influence how rapidly pellets dry
and change color (Larrucea 2007, p. 9). Sightings of individual pygmy
rabbits do confirm current activity, but observers should be
experienced as the young of cottontails (Sylvilagus spp.) and
jackrabbits (Lepus spp.) can be confused with pygmy rabbits. Sightings
of pygmy rabbits are difficult and do not occur often due to the dense
vegetation inhabited, limited home ranges, and their elusive nature
(Larrucea 2007, p. 10). Road transect surveys are inefficient for pygmy
rabbits due to their reluctance to cross open areas and roads
(Bradfield 1975, p. 3). Pygmy rabbits are more likely to run a short
distance, sit tight, or disappear into a burrow than to run for a long
distance making detection more difficult (Larrucea 2007, p. 10).
We are also aware of difficulties in interpreting site activity
during surveys. For example, in Montana, Lenard et al. (2005, p. 9)
commented that comparisons of active to inactive burrows may be
complicated, stating that burrows exhibiting current rabbit activity
were easier to locate because tracks in the snow made them very
apparent. The relative difference in abundance between currently active
and recently active should not be interpreted to indicate any level of
past versus current activity. Flinders et al. (2005, p. 33), in Utah,
commented that single burrow systems are harder to detect than multiple
entrance burrow systems. The Bureau of Land Management (BLM) (2007a, p.
1) used the Ulmschneider et al. (2004, entire) method and noted that
this type of inventory covered large expanses and typically found the
larger pygmy rabbit populations and a small subset of the actual burrow
systems on a particular site. However, when sites were re-inventoried
intensively, BLM found numerous additional burrow systems. Lee et al.
(2008, pp. 4-5), in Utah, commented that using criteria from Rachlow
and Witham (2004b, pp. 6-7) or Ulmschneider et al. (2004, entire) is
somewhat inaccurate in predicting current pygmy rabbit burrow
utilization. Lee et al. (2008, p. 5) used remote cameras to verify the
presence or absence of pygmy rabbits in comparison to burrow
classification. By using both burrow classifications methods along with
remote cameras, refinement of burrow classifications and census
techniques may be possible in the future.
Bartels (undated) compared active and passive survey methods for
detecting pygmy rabbit burrow occupancy at what she considered isolated
and low density sites. She compared the use of an active survey method
(peeper probe) and a passive survey method (surface classification of
burrows using sign (burrows, pellets) to determine occupancy by pygmy
rabbits (Bartels undated, pp. 3-4). A total of 233 burrows were
compared on 27 sites in Oregon and Idaho. Under the passive method, all
233 burrows were considered occupied (Bartels undated, p. 5). Under the
active survey method, 122 (52.4 percent) of the burrows were classified
as occupied and as recently occupied, and 111 (47.6 percent) were
classified as unoccupied (Bartels undated, p. 5). Bartels (undated, p.
7) recommended use of an active survey method in areas where pygmy
rabbit numbers appear to be low and isolated sites are found. Viewing
the internal attributes of burrows and establishing a standard for
occupancy increases survey accuracy and could lead to greater accuracy
when monitoring pygmy rabbit occupancy over time.
We must also take into consideration complicating factors when
interpreting current distribution and/or status as we do not have a
complete understanding of pygmy rabbit habitat use. For example, it
appears that some habitat use may be seasonal and pygmy rabbits may be
somewhat migratory as some burrow systems appear occupied during
certain times of the year and inactive during others, or from year to
year (Flinders et al. 2005 p. 35; Bockting 2007 p. 2; Larrucea 2007,
pp. 96-97). Flinders et al. (2005 p. 35) reported that areas where
pygmy rabbits were relatively abundant in Utah suddenly became sparse
after the juveniles dispersed. Other areas then appeared to indicate an
increase in the numbers of pygmy rabbits. In Utah, Flinders et al.
(2005, p. 32) found active burrows were more common than the other
activity classifications (i.e., recent, old, very old), and thus
support statements that pygmy rabbits use more than one burrow system.
He thought inactive burrows likely play an important role in providing
escape cover. Cameras placed on burrows classified as old or very old
documented use by pygmy rabbits. Larrucea (2007, p. 7) also
photographed pygmy rabbits at sites where burrows were determined to be
inactive.
After reviewing the available information, we consider our approach
in using information to determine the status of the pygmy rabbit to be
conservative. We have used these data to compare historical (1999 and
earlier) to current (2000 and later) distribution patterns. We have
used the data to compare activity levels (active; inactive) of sites or
burrows during these two time periods. Questions have been raised
regarding surveyors' abilities to accurately determine activity level
due to possible detection differences, absence of long-term site
monitoring, and our incomplete understanding of the pygmy rabbit's life
history requirements (e.g., possible seasonal use of some areas or
periods of burrow non-use). We are also aware that some
[[Page 60523]]
survey techniques provide better data than others. Though these data
are limited in their usefulness for our purposes due to their local,
short-term nature, they are understood, by the Service to be the best
available information. This data does provide baseline information that
could be the foundation for future survey and monitoring efforts.
Models
To facilitate pygmy rabbit surveys in recent years, models of
potential habitat have been developed for some States or study areas.
Eliminating areas in these models that are unsuitable can be important
as it can concentrate efforts and resources in areas that are more
likely to support pygmy rabbits (Gabler et al. 2000, p. 763). Large
areas that seem to be appropriate pygmy rabbit habitat may not be
suitable based on the specific habitat characteristics needed for pygmy
rabbits (Gabler et al. 2000, p. 763). To aid pygmy rabbit research in
Oregon, modeling efforts have been conducted by the following
researchers: Bartels (2003, p. 35) for the BLM Burns District using
GIS; Meisel (2006, p. 4) for the Hart Mountain National Antelope
Refuge; and Hager and Lienkaemper (2007, pp. 1-2) for large blocks of
State land.
In Idaho, modeling efforts have been conducted by Rachlow and
Svancara (2006, p. 828); Bartels (2003, pp. 35-38), and Gabler et al.
(2000, pp. 762-763; 2001 entirety). In Montana, Lenard et al. (2005, p.
1) reported on the development of four predictive models in Montana. In
Wyoming, Purcell (2006, p. 28) used a probabilistic distribution map
developed by Keinath and Thurston (2005, cited in Purcell 2006, p. 28)
using the combination of two models, DOMAIN (environmental similarity
method) and CART (classification and regression tree analysis). Based
on data collected during Purcell's study, a new predictive distribution
model was created (Purcell 2006, p. 31).
In Nevada, a predictive equation was produced based on habitat data
collected and used as a model to characterize habitat where pygmy
rabbits or sign occurred. The model explained the occurrence of pygmy
rabbits or their sign on 56.7 percent of transects (Himes and Drohan
2007, p. 376). Larrucea and Brussard (2008a, p. 693) used GIS
coverages. In Utah, Lee et al. (2008, p. 3) used vegetation data from
the 2004 Southwestern Regional Gap Analysis Project. In general, these
models are helpful in focusing survey efforts over a large area;
however, researchers also recognize that due to scale and available
data for particular attributes such as soils and vegetation, only on
the ground surveying can positively indicate pygmy rabbit presence
(Bartels 2003, pp. 92-94; Meisel 2006, pp. 26, 48; Lenard et al. 2005,
p. 1).
We believe our large-scale, rangewide analysis, based on the
Service's databases, represents the best scientific and commercial
information available on the distribution of pygmy rabbits. As
mentioned above, many individual records were considered but not
included in the Service's databases for the following reasons: database
records showing some level of uncertainty for the information being
provided (e.g., other leporid species data included; uncertainty about
whether pygmy rabbit was observed or other leporid species; using words
such as ``possible'', ``potential'', ``maybe'', ``unsure''); records
that only provided location data or indicated pygmy rabbit sign with no
additional information indicating what type of sign (e.g., burrow,
pellet, track, sighting of animal as relates to reliability) had been
observed; records related to telemetry locations (while informative in
determining an individual's distribution within its home range, this
provides little information at the larger landscape scale used here; we
did include the capture location of any individual pygmy rabbit trapped
and fitted with a radio collar); records based solely on pellets or
tracks due to concerns with species misidentification; those lacking
key information (e.g., year which is needed for trend analysis); and
duplicate records.
Eliminating records with these types of concerns provides for a
more accurate representation of pygmy rabbit range-wide distribution
rather than including all records without considering some level of
reliability of the data. While pygmy rabbits likely occur in additional
unsurveyed areas and even in some areas that have been surveyed (pygmy
rabbit sign can be easily overlooked), we have made our finding based
on our review of these databases, which represent the best scientific
and commercial information available.
Distribution by State
The following distribution and trend discussion is based on
information obtained from published and unpublished literature and an
interpretation of the survey location point data compiled in the
Service's databases. The following review does not discuss every
document from the various information sources due to the volume, but a
selection of literature that provides substantive historical
information and survey information on a large scale. The literature is
generally, but not entirely, associated with records included in the
Service's databases. This is because not all reports provided specific
location points and not all location points are associated with a
report, and as stated earlier, some records are not included in the
Service's databases. This analysis compares our understanding of the
historical and current ranges of the pygmy rabbit discussed in this
finding.
Oregon
The earliest pygmy rabbit records for the State of Oregon include:
two specimens collected in Callow Valley, Harney County, Oregon (Nelson
1909, p. 278); specimens collected near Ironsides, Malheur County,
Oregon in 1911-1912 (Anthony 1913, pp. 20-21); and 10 specimens
collected near Baker, Baker County, Oregon (Dice 1926, p. 27).
Bailey (1936, pp. 110-111) indicated that pygmy rabbits in Oregon
extended from the southern foothills of the Blue Mountain Plateau and
eastern base of the Cascade Range over the southeastern quarter of the
State. He reported that they were absent from areas of open country
where sagebrush and rabbit brush were not abundant. As a result, there
are numerous wide gaps in their range.
Brodie and Maser (1966, pp. 11-12) reported the contents from owl
pellets collected in 1966 at Lower Bridge, Deschutes County, Oregon.
Prey animals consisted of pygmy rabbits. This location was reported as
a new location for the pygmy rabbit as the nearest previously
documented location was Redmond, Oregon (Hall and Kelson 1959, cited in
Brodie and Maser 1966, p. 12) about 10 miles (16.1 km) east of Lower
Bridge.
Olterman and Verts (1972, p. 25) listed 37 museum records for
Oregon which occurred in general near the following areas: Baker, Baker
County; Paulina, Crook County; Redmond, Deschutes County; Beakley,
Beaties Butte, Burns, Rock Creek Ranch, Crane, Drewsey, Narrows,
Sageview, Mud Lake, Steens Mountain, Voltage, and Waverly, Harney
County; Fremont and Klamath Falls, Klamath County; Adel, Ft. Rock,
Guano Creek, Guano Valley, Rabbit Creek, andSilver Lake, Lake County;
and Cold Springs, Cow Creek Lake, Ironside, Mahogany Mountains,
Malheur, McDermitt, Riverside, and Rome, Malheur County. At the time of
their writing, Olterman and Verts (1972, p. 25) indicated recent
observations by biologists demonstrated that pygmy
[[Page 60524]]
rabbits were occurring over the same area as in the past. Pygmy rabbits
were observed near Hines, Wagontire, Lakeview, Hart Mountain National
Antelope Refuge, Hampton, Ft. Rock, and Lower Bridges.
Bradfield (1974, p. 39) also spent time at Ironside, in Malheur
County, Oregon. He found evidence of previous pygmy rabbit use, but no
fresh sign of use or rabbits, which supported his belief that they were
in decline on a larger geographic scale.
Weiss and Verts (1984, p. 563) attempted to search for pygmy
rabbits in Oregon based on museum record information for sites listed
in Olterman and Verts (1972, p. 25). Because of the generality of the
location descriptions provided, they also reviewed aerial photography
and soil maps to assist in narrowing searches in the areas described
where pygmy rabbits had been collected previously (Weiss and Verts
1984, p. 564). Evidence of pygmy rabbits was found at 51 of 211 areas
searched in 1982 (Weiss and Verts 1984, p. 566). In 1983, only 5 of the
15 sites that had been sampled for soil and vegetation information in
1982 showed recent pygmy rabbit activity (Weiss and Verts 1984, p.
566). Of 51 burrows found at 5 of the sites occupied in 1982, 19
burrows were found open in 1983 and 8 had fresh pellets (Weiss and
Verts 1984, p. 568). Only the locations of the 15 occupied sites in
Grant and Lake Counties where Weiss and Verts (1984, p. 566) recorded
vegetation and soil data are provided in their document.
Since 2000, additional survey efforts have been conducted. Bartels
(2003, p. 70) visited 54 previously known pygmy rabbit sites located on
BLM lands in 2000 and 2001 in Harney, Malheur, Lake, and Deschutes
Counties, Oregon. Results from these visits showed 12 sites were
occupied, 8 were of undetermined occupancy, and 34 showed no occupancy.
Three additional sites were surveyed off of BLM lands. One site was
occupied, one showed no evidence of pygmy rabbit use, and one was
considered undetermined and warranted further investigation (Bartels
(2003, p. 86). Some of these sites included those visited by Weiss and
Verts (1984, p. 564) (Bartels 2003, p. 91).
BLM conducted surveys on their Lakeview and Vale Districts in
Harney and Lake Counties, Oregon in 2002 and 2003 (BLM 2003a, p. 1).
Forty-five sites were surveyed in fall of 2002 and winter 2003 on the
Lakeview District with 19 sites indicating pygmy rabbit activity (10
active, 9 inactive). Twenty sites were surveyed in fall of 2002 and
winter 2003 on the Vale District with two sites indicating pygmy rabbit
activity (1 active, 1 inactive). The remaining sites surveyed (44) on
the two districts in fall of 2002 and winter 2003 showed no evidence of
pygmy rabbit use (BLM 2003a, p. 1). During the summer of 2003, 23
additional sites were surveyed and 19 showed pygmy rabbit activity (11
active, 8 inactive); 4 sites showed no evidence of pygmy rabbit use
(BLM 2003a, no page number provided). BLM continued to conduct surveys
on their Burns and Lakeview Districts in Harney and Lake Counties,
Oregon, respectively, in 2005 and 2006 (BLM 2006a, pp. 3-4); active
pygmy rabbit use was found at four of the seven sites surveyed. In 2006
and 2007, BLM surveyed 12 additional sites on the Lakeview District,
and active pygmy rabbit use was found at 8 sites (BLM 2007b, p. 1).
Various numbers of burrow systems were found at the different sites
(BLM 2003a, p. 3; BLM 2006a, pp. 3-4; BLM 2007b, pp. 3-6).
Meisel (2006, p. 4), improved the known distribution of pygmy
rabbits at Hart Mountain National Antelope Refuge, Lake County, during
2004 and 2005. The sagebrush habitat on the refuge has been protected
from development and other human disturbances for at least 70 years
(Meisel 2006, p. 9). Remote infrared 35-mm cameras were used to confirm
occupancy by pygmy rabbits (Meisel 2006, p. 12). Habitat
characteristics were measured at 45 occupied burrows (Meisel 2006, p.
18). In 2005, refuge staff found approximately 99 occupied burrows near
burrow locations that were found in 2004 by Meisel (R. Huddleston-
Lorton, cited in Meisel 2006, p. 27). Location information on these 99
burrows was not included in Meisel (2006). It is possible that a large
population inhabits the northeast portion of the refuge (Meisel 2006,
p. 27). Meisel (2006, p. 27) recommends future research be conducted in
areas of Wyoming big sagebrush to locate all burrows and document the
population status on the refuge which is currently unknown.
Hager and Lienkaemper (2007, p. 1) conducted surveys to determine
the presence or absence of pygmy rabbits on State lands in Malheur,
Harney, Lake, and Deschutes Counties. One hundred and fifty-seven sites
were ground surveyed during 2004 and 2005 (Hager and Lienkaemper 2007,
p. 3). Of the 157 sites, 18 were determined to be active, 14 inactive,
and 125 showed no evidence of pygmy rabbit presence (Hager and
Lienkaemper 2007, pp. 4-5).
Most historical records (1999 and earlier) for Oregon occur in the
following counties: Malheur, Harney, and Lake. A few historical records
also occur in Baker, Grant, Crook, Deschutes, and Klamath Counties.
There is also a 1992 database sighting record for Jefferson County.
Current information (2000 and later) indicates Malheur, Harney, and
Lake as well as Klamath and Deschutes Counties continue to support
pygmy rabbit activity. We are unaware of information indicating any
recent survey efforts have been conducted to determine pygmy rabbit
activity for Baker, Grant, or Jefferson Counties. Baker County
indicated some activity in 1926. Grant County indicated inactivity
during 1982 and 1983. Jefferson County had some activity in 1992. The
southeastern portion of Crook County was searched during 2005 by BLM,
but pygmy rabbit evidence was not found. In general, pygmy rabbit
activity continues to occur in southeastern Oregon in a similar
distributional pattern as compared with historical information.
Idaho
Merriam (1891) was the first to describe the ``Idaho pygmy rabbit
(Lepus idahoensis)'' based on a specimen collected on September 16,
1890, along the upper part of the Pahsimeroi River by Basil Dutcher
(Merriam 1891, pp. 7, 13, 75-78). Merriam (1891, p 75) indicated that
the general distribution for the pygmy rabbit was the ``Sage Plains''
along the Snake River, and in Birch Creek and Lemhi Valleys, Little
Lost River Valley, Pahsimeroi Valley and Big Lost River Valley, Idaho
and into northern Nevada to the south, and to the west ``probably''
into eastern Oregon and Washington.
Other early records include: six specimens collected from Big Lost
River Valley, Birch Creek, Junction, Lost River Mountain, and
Pahsimeroi Valley, Idaho (Nelson 1909, p. 278); and a report of two
pygmy rabbits collected from 1 mi (1.6 km) west of Schutt's Mine in
November 1930 (Whitlow and Hall 1933, p. 269). In May 1931, a female
was collected near Trail Creek (Whitlow and Hall 1933, p. 270). These
records extended the known range by 75 mi (120.7 km) to the southeast
(Whitlow and Hall 1933, p. 270). Observations of pygmy rabbits in Idaho
occurred near the head of the Pahsimeroi River, Idavada, Pahsimeroi
Valley, Riddle, and Pocatello (Davis 1939, p. 364). Davis lists
locations of 10 specimens examined: Owyhee County, near Riddle, 2;
Cassia County, Elba, 1; Butte County, Craters of the Moon National
Monument, 1; Power County, near Michaud, 3; Bannock County, near
Schutt's Mine, 2; Trail Creek near Pocatello, 1. Additional records
mentioned included Nelson's (1909)
[[Page 60525]]
records of Lemhi County, Junction; Custer County, Pahsimeroi Valley.
Additional locations included Minidoka County, Minidoka (Seton 1929,
cited in Davis 1939, p. 366); Cassia County, Burley (Grinnell et al.
1930, cited in Davis 1939, p. 366); Clark County, Birch Creek; Butte
County, Big Lost River Valley; Lost River Mountains (Lyon 1904, cited
in Davis 1939, p. 366). Lyon (1904, cited in Davis 1939, p. 366) also
includes a record from Ione Valley. Davis (1939, p. 366) was unable to
find Ione Valley in Idaho and thought the specimen may have been from
Nevada.
Bradfield (1974, p. 39) speculated that the pygmy rabbit population
was declining in his study area in Bingham County, Idaho. This was
based on the number of abandoned burrows, number of skulls indicating
death by predation or other means, and fewer observed rabbits.
In her Idaho study area in portions of Idaho National Engineering
and Environmental Laboratory (Laboratory) in Butte and Jefferson
Counties, Gabler (1997, p. 42) found 101 burrow sites, of which 26 were
active. Gabler (1997, p. 94) also revisited Wilde's (1978) three study
areas on Laboratory lands, and found two collapsed burrows with no sign
of occupancy; four active burrows which were abandoned 10 months later;
and 34 abandoned burrows, respectively.
Several surveys were conducted by Roberts between 1997 and 2004. In
1997 and 1998, Roberts (2001, pp. 4-6) conducted surveys on BLM lands
administered by the Salmon and Challis Field Offices (FO) in Lemhi and
Custer Counties. The 3 areas occurred in the upper Lemhi River and
upper Birch Creek Valleys; upper Pahsimeroi River and upper Little Lost
River Valleys; and the upper Warm Springs Creek and upper Big Lost
River Valleys. He found that pygmy rabbits were found widely scattered
in all 3 of these areas (Roberts 2001, pp. 10-11). In addition, Roberts
(2001, p. 11) mentioned an occupied area in Railroad Canyon adjacent to
Bannock Pass. This may be contiguous with habitat found in Horse
Prairie Creek, Montana reported by Rauscher (1997, p. 13). Other areas
of occupied rabbit habitat were found in Hawley Creek and in Bradshaw
Basin (Roberts 2001, p. 11). During 2002, Roberts (2003a, pp. 3, 5)
conducted surveys in the Snake River Plains area in southern Idaho.
Surveys were conducted on BLM lands within Idaho Falls, Pocatello,
Shoshone, Owyhee, Jarbidge, and Burley FO areas, on U.S. Forest Service
(USFS) lands within Targhee, Caribou, Cache, Sawtooth, Salmon, and
Challis National Forests, and the Curlew National Grasslands. Roberts
(2003a, p. 6) found 9 currently active pygmy rabbit burrow systems.
Four were found on the Owyhee FO, two on the Pocatello FO and one each
in Idaho Falls and Jarbidge FO areas. One was found on the Curlew
National Grasslands. Two systems were classified as recently active.
One was found on the Owyhee FO area and the other on the Shoshone FO
area.
During the summer of 2003, Roberts (2003b, p. 3) searched areas in
Big Lost River Valley, Little Lost River Valley, Birch Creek, and
Medicine Lodge Creek for pygmy rabbits. He found three currently and
recently active burrow sites in Big Lost River Valley; seven currently
and recently active burrows in Little Lost River Valley; seven
currently active burrow sites in Birch Creek where five pygmy rabbits
were observed; and one currently active burrow site at Medicine Lodge
Creek area. Another active burrow site was found in upper Medicine
Lodge Creek (Targhee National Forest 3 miles from Bannock Pass).
In 2004, Roberts (2004, p.2) continued to survey areas in Big Lost
River Valley, Little Lost River Valley, Birch Creek, and Medicine Lodge
Creek located in Butte and Clark Counties. He was unable to find pygmy
rabbit evidence in the areas he searched in Big Lost River (Roberts
2004, pp. 3-4). He found 11 currently active sites in Little Lost River
area. In the Birch Creek area he found 7 currently and recently used
sites. He saw 6 pygmy rabbits at one of these areas. In this area, the
pygmy rabbits were using cracks and crevices in and around large rocks
and boulders as their burrows. In the Medicine Lodge Creek area he
found 10 new burrow sites. He found 2 active burrows on the Targhee
National Forest. Two additional active burrow sites were found on the
U.S. Sheep Experiment Station.
White and Bartels (2002, p. 1) surveyed for pygmy rabbits on 11
grazing allotments in Twin Falls and Cassia Counties on BLM lands
administered by the Burley FO. Results included 35 burrows found on 6
of the allotments (White and Bartels 2002, p. 5). Twenty-four of the
burrows were revisited with a peeper probe and six burrows located on
two allotments were considered occupied by pygmy rabbits (White and
Bartels 2002, p. 5). In addition, White and Bartels (2002, p. 7)
attempted to visit 31 historical locations for pygmy rabbits in Cassia,
Minidoka, Blaine, Power, and Oneida Counties, Idaho. Eighteen sites
were too vague to relocate, eight were disturbed due to various
factors, and five were potentially suitable habitat (White and Bartels
2002, pp. 7-8). No active pygmy rabbit burrows were found on any of the
13 disturbed or potentially suitable sites visited.
Red Willow Research Inc. conducted several surveys between 1999 and
2004. In 1999, Red Willow Research Inc. (2000, pp. 5-6) reported on
sightings of pygmy rabbits at five locations in Cassia and Oneida
Counties. Red Willow Research Inc. (2002, pp. 99-100) reported that all
nine study areas within the BLM Shoshone FO area showed presence of
pygmy rabbit use. Recent or current signs of occupancy were found at
five individual sites along transects within three of the nine study
areas in 2001 and 2002. Red Willow Research Inc. (2004, p. 3) continued
surveys in and adjacent to the nine study areas identified in the 2002
study. The 2004 survey resulted in one sighting and one possible
sighting of a pygmy rabbit, one inactive burrow system, and
identification of additional areas for future survey efforts (Red
Willow Research Inc. 2004, p. 4).
North Wind, Inc. (2004, p. 2) surveyed for pygmy rabbits on BLM
lands in eight areas located in the northern portions of the BLM Idaho
Falls District. Five sites indicated recent or past pygmy rabbit use,
including a pygmy rabbit sighting (North Wind, Inc. 2004, p. 13).
Rachlow and Witham conducted several surveys between 2003 and 2006.
Rachlow and Witham (2004a, p. 2) surveyed 12 locations in Camas,
Blaine, and Gooding Counties, south central Idaho that had been
identified as potential habitat in 2003. Two sites were confirmed to
support pygmy rabbit populations. Witham and Rachlow (2004, p. 3)
surveyed three potential sites at Craters of the Moon National Monument
and Preserve in 2004 and found no evidence of pygmy rabbit presence.
Rachlow and Witham (2005, p. 1) conducted a pilot study to test whether
pygmy rabbit sign could be detected during aerial surveys in the Camas
Prairie of south central Idaho. The study area included the two
previously known locations found in 2003 and confirmed in 2004 by
Rachlow and Witham (2004a, pp. 2-3) (Rachlow and Witham 2005, p. 2).
The aerial surveys identified 25 potential sites and 21 were ground
checked (Rachlow and Witham 2005, p. 7). Seven of the 21 sites were
confirmed to support pygmy rabbit populations (Rachlow and Witham 2005,
p. 7). Rachlow and Witham (2006, p. 1) surveyed a portion of the Camas
Prairie in south central Idaho by fixed-wing aircraft during February
2006. They identified 67 potential sites from the air and evaluated 64
of them on the ground. Presence of pygmy rabbits was
[[Page 60526]]
confirmed at 32 sites. Sign at the remaining sites was attributed to
cottontail rabbits or other species. These new locations expanded the
known distribution of pygmy rabbits in the Shoshone FO area.
BLM (2005a, p. 1) reported on surveys conducted between 2002 and
2005 on BLM lands within the Boise District (Owyhee FO). In 2002, four
survey routes were walked and pygmy rabbit evidence was observed on
each route (BLM 2005a, p. 2). Two sites were at or near previously
known locations and two were new locations. One site was considered
active. In 2003, 25 routes were walked and 12 locations found (7 active
or recent, 5 inactive) (BLM 2005a, p. 2). In 2004, 14 routes were
walked and 2 new populations were found (1 active or recent, 1
unrecorded activity level) (BLM 2005a, p. 2). In 2005, 242 routes were
walked with 16 new populations found (9 active or recent, 7 inactive)
(BLM 2005a, p. 2).
Bartels (2005, p. 2) conducted pygmy rabbit surveys in the southern
portion of BLM's Jarbidge FO area during 2005. Sixteen pygmy rabbit
burrows were identified with an additional 25 documented as potential
pygmy rabbit burrows. Burrows were generally located near Coonskin
Butte, Pigtail Butte, Dorsey Table, Worley Draw, and Signal Butte.
During the survey four pygmy rabbits were confirmed observed. These
rabbits were observed at Worley Draw and Coonskin Butte.
Waterbury (2005, p.3) conducted winter surveys in late 2004 and
early 2005 for pygmy rabbits in areas previously identified as
potentially suitable habitat but where their presence or absence had
not been conclusively determined on BLM (Salmon and Challis FO) and
USFS (Leadore, North Fork, and Challis Ranger Districts) lands. Of the
38 locations surveyed, pygmy rabbits were present at 12 of them
(Waterbury 2005, p. 4). Waterbury (2006, p. 5) expanded search areas
compared with previous efforts on BLM lands (Challis FO) located in
Custer and Lemhi Counties. Surveys documented 269 positive detections
of pygmy rabbits (burrows, tracks, pellets, sightings) over 20 areas
(Waterbury 2006, pp. 9, 27-32). The areas of greatest concentrations
occurred in Big Lost River Valley, Thousand Springs Valley, Pahsimeroi
River Valley, Upper Spar Canyon, and Upper Road Creek (Waterbury 2006,
p. 9). Forty-six pygmy rabbits were observed during the study
(Waterbury 2006, p. 9). Of the 265 positive detections associated with
burrow systems, 91 percent were at active or recently active systems
(Waterbury 2006, p. 9). These surveys expanded the known pygmy rabbit
locations in the Challis FO and confirmed the persistence of historical
populations in the Upper Pahsimeroi and Thousand Springs Valleys
(Waterbury 2006, p. 11).
Wackenhut (2008, pp. 4, 6, 7) conducted pygmy rabbit surveys across
much of Bear Lake Plateau, Bear Lake County, Idaho between December
2006 and March 2007. Information was collected on 568 active burrows in
19 different locations across the plateau. Ten pygmy rabbits were
sighted during the study. Fecal pellets were collected at 19 individual
burrows. DNA analysis for pygmy rabbit was positive for 13 of these
samples; 5 samples were positive for mountain cottontail and 1 sample
failed (Wackenhut 2008, p. 4).
Most of the historical records (1999 and earlier) for Idaho occur
in the following counties: Owyhee, Cassia, Minidoka, Bannock, Bingham,
Butte, Custer, and Lemhi. Additional records are from Canyon, Ada, Twin
Falls, Lincoln, Power, Oneida, Blaine, Bear Lake, and Clark. Current
information (2000 and later) indicates the following 11 counties
continue to support pygmy rabbit activity: Owyhee, Twin Falls, Cassia,
Bear Lake, Lincoln, Blaine, Bingham, Butte, Custer, Lemhi, and Clark.
Active areas were also found in the following counties without previous
records: Washington, Gooding, Camas, Jefferson, and Fremont. Payette
County indicated a recent inactive area.
We are uncertain of the current pygmy rabbit activity in Canyon,
Ada, and Bannock Counties because we are unaware of any survey efforts
in 2000 or later occurring in these counties. Limited recent survey
effort in Minidoka, Power, and Oneida Counties indicate inactivity at
previously known sites. Records from Canyon and Ada Counties indicate
activity in 1915 and 1982, respectively. Power and Minidoka Counties
indicate activity in the 1930's and 1940's, respectively. Both Bannock
and Oneida Counties indicate activity in the 1990's. However, recent
survey efforts have expanded the known distribution in this State.
Numerous previously unknown locations currently show signs of pygmy
rabbit occupancy including locations in previously undocumented
counties.
Montana
The pygmy rabbit was first documented in Montana in 1918 (Hoffman
et al. 1969, cited in Rauscher 1997, p. 1). In 1963, a specimen was
collected in Big Sheep Basin (Rauscher 1997, p. 1). Between 1963 and
1997 no additional documentation regarding the pygmy rabbit in Montana
occurred (Rauscher 1997, p. 1).
Rauscher (1997, entirety) documented the results of pygmy rabbit
surveys in Montana during 1996 and 1997. Pygmy rabbits occupied
suitable habitat in most of Beaverhead County, the extreme southern end
of Deer Lodge County, and the western edge of Madison County (Rauscher
1997, p. 5). Because of the discontinuous distribution of pygmy
rabbits, every occupied site may not have been found, and as a result
pygmy rabbits may occur outside of this range (Rauscher 1997, p. 5).
Five of six historical sites were searched and four showed signs of
occupation (Rauscher 1997, p. 6). He mentioned some sites were found
that no longer appeared to be occupied. These occurred west of Dillon,
at the southern end of Dutchman Mountain, and at the northern edge of
Frying Pan Basin (Rauscher 1997, p. 6). Rauscher concluded pygmy
rabbits appeared to occupy much of the historical range (Rauscher 1997,
p. 13).
Janson (2002, p. 33) wrote that the historical range in Montana
continues to support pygmy rabbits, with some exceptions. This was
based on his limited observations in Beaverhead County, Montana in
2001.
During 2004 and 2005, the Montana Natural Heritage Program
conducted pygmy rabbit surveys for BLM (Dillon FO) to assess current
distribution in the State (Lenard et al. 2005, p. 1). These surveys
focused on Beaverhead (2004) and Madison (2005) Counties in areas of
known use and areas where no activity had been previously documented
(Lenard et al. 2005, p. 1). Due to snow, known locations in Horse
Prairie, Medicine Lodge Creek (south of Ayers Canyon), Badger Gulch/
Sagebrush Creek, and Upper Ermont Creek were inaccessible (Lenard et
al. 2005, p. 1). New areas of pygmy rabbit activity were identified,
expanding the current known distribution of the species (Lenard et al.
2005, p. 1). In 2004, five previously known locations were surveyed and
four of the five indicated current activity in Beaverhead County. The
fifth showed recent activity (Lenard et al. 2005, pp. 9-10). Seven new
areas were surveyed and all showed current pygmy rabbit activity
(Lenard et al. 2005, p. 10).
In Madison County, five areas were surveyed in 2005. Although a few
pygmy rabbit locations had been previously documented in one of these
areas, the remaining areas were previously unknown to surveyors
regarding pygmy rabbit occupancy. Of these five areas, three areas
showed current activity; two areas showed recent activity (Lenard et
al. 2005, p. 12). Four new areas were surveyed and
[[Page 60527]]
three areas were reported as showing no pygmy activity; one area could
indicate a dispersal area as pellets were found but no burrows (Lenard
et al. 2005, pp. 12-13).
In Montana, during the winter of 2007, pygmy rabbit surveys were
conducted in areas where no prior surveys had been conducted or where
recent activity had not been documented in Beaverhead and Deer Lodge
Counties (Hendricks et al. 2007, p. 3). Twenty-four sites were surveyed
and four sites were found to have current pygmy rabbit activity
(Hendricks et al. 2007, p. 9). Twelve sites had no evidence of pygmy
rabbit activity, eight were considered unsuitable habitat for pygmy
rabbits, and two were considered potential but were inaccessible due to
snow (Hendricks et al. 2007, p. 9). Two active sites in Big Hole Valley
were notable as they indicated current activity at sites that had not
been resurveyed since they were active in 1997 (Hendricks et al. 2007,
p. 10). The two other active sites were previously undocumented pygmy
rabbit sites (Hendricks et al. 2007, p. 11). These new sites occurred
in gaps between other locations suggesting additional locations may be
found between those currently known (Hendricks et al. 2007, p. 13). The
distribution and status of pygmy rabbits in Montana has become clearer
since 1997 (Hendricks et al. 2007, p. 15). However, Hendricks et al.
(2007, p. 15) suggested additional surveys should occur in Centennial
Valley, Jefferson River corridor north of Twin Bridges, Frying Pan
Basin west of Dillon, and the Ruby River and Sweetwater Creek
corridors.
Most of the historical and recent records for Montana occur in the
following two counties: Beaverhead and Madison. Current information
(2000 and later) indicates these two counties, as well as Deer Lodge
County, continue to support pygmy rabbit activity. There is a notable
increase in the current distribution of the pygmy rabbit to the
northeast in Madison County.
Wyoming
During the 1980's and 1990's a few reports documented pygmy rabbits
in Wyoming. Campbell et al. (1982, p. 100) were the first to confirm
the existence of pygmy rabbits in Wyoming. In 1981, 6 specimens were
collected, 17 individuals were observed, and 2 skulls and many pellets
were found at 2 sites in Uinta and Lincoln Counties in southwestern
Wyoming (Campbell et al. 1982, p. 100). These two new locations found
in Wyoming extended the known range of the pygmy rabbits about 149 mi
(240 km) to the southeast and 90 mi (145 km) to the northeast (Campbell
et al. 1982, p. 100). Clark and Stromberg (1987, p. 75) reported three
sites from Lincoln and Uinta Counties located in southwestern Wyoming.
Garber and Beauchaine (1992, p. 3) compiled previously reported
observations from Campbell et al. (1982, p. 100) and information from
the Wyoming Game and Fish Department database. Although, this report
does not indicate locations, which ones were revisited, or their
status, several sites were revisited and new sites were found in 1990.
Eleven new observations were recorded which increased records to 50
site confirmations (Garber and Beauchaine 1992, p. 4). Documented
observations expanded the known distribution in Wyoming by including
two additional counties: Sublette and Sweetwater (Garber and Beauchaine
1992, p. 8).
In 2004 and 2005, Purcell (2006, pp. 1, 7-11, 30) conducted her
study in 10 areas in Lincoln, Sublette, Sweetwater, Fremont, and Carbon
Counties. She found pygmy rabbits more widely distributed in
southwestern and south central Wyoming than formerly thought due to
previously unknown locations being found in Fremont and Carbon
Counties. Purcell (2006, p. 32) suggested pygmy rabbits in Wyoming
could occur as far east as Rawlins, as far north as Riverton, and as
far south as Baggs.
Western EcoSystems Technology, Inc. (2006, p. 1) conducted a pygmy
rabbit survey in Lincoln and Uinta Counties, Wyoming. During the
survey, 88 pygmy rabbit points indicating sign of pygmy rabbit presence
were documented.
Aster Canyon Consulting, Inc. conducted several surveys between
2005 and 2007 in relation to proposed oil and gas facilities in
Wyoming. These surveys provide pygmy rabbit sightings and signs in
Lincoln, Sublette, and Sweetwater Counties.
Grasslands Consulting, Inc. (2007, pp, 1,2) conducted pygmy rabbit
surveys in 2007 in relation to three proposed oil and gas facilities in
Sweetwater and Uinta Counties, Wyoming. These surveys provided pygmy
rabbit sightings and signs in these counties.
Most of the historical and recent records for Wyoming occur in the
following four counties: Uinta, Lincoln, Sublette, and Sweetwater.
Current information (2000 and later) indicates these counties continue
to support pygmy rabbit activity. Recent survey efforts have expanded
the known distribution in this State considerably as numerous
previously unknown areas have been found in southern Sublette, southern
Fremont, and eastern Sweetwater Counties. Areas in western Carbon
County indicate a further range extension of the known distribution.
California
Early records indicate that pygmy rabbits were documented in
eastern Modoc, Lassen, and Mono Counties. Henshaw (1920, p. 9)
mentioned obtaining rabbit specimens in northeastern California at
Goose Lake, Modoc County, in 1877 (at the time identified as
Trowbridge's hare (Lepus trowbridgei) but later determined to be
Brachylagus idahoensis as described by Merriam). Grinnell et al. (1930,
p. 553) collected 20 pygmy rabbit specimens during 1926 and 1928 in the
vicinity of Ravendale, Lassen County. Orr (1940, p. 195) observed pygmy
rabbits on the south edge of the Madeline Plains, located east of
Ravendale, in October 1931. Severaid (1950, pp. 1-2) recorded
observations and collection in 1948 of pygmy rabbits at Bodie, a famed
gold mining ghost town, located in northern Mono County. The southern
limit of their distribution in California was documented in 1955 in the
vicinity of Crowley Lake in southern Mono County (Jones 1957, p. 274).
During 2004, surveys were conducted on lands managed by BLM (Eagle
Lake FO) in northern California (Sequin 2004, entirety). Twenty
historical records are documented within the boundaries of the Eagle
Lake FO and were located near Ravendale based on information provided
by Grinnell et al. (1930) and Orr (1940). Pygmy rabbits were not found
at any of the historical sites; no evidence of old or fresh pellets or
burrows were seen (Sequin 2004, p. 6). Sequin (2004, p. 6) also
surveyed 356 potential sites for pygmy rabbit sign within the Eagle
Lake FO boundary. No pygmy rabbit activity, either old or current, was
found at any of these potential sites (Sequin 2004, p. 6). As all
potential pygmy rabbit habitat was not surveyed, it is possible that
pygmy rabbits may still be found within the Eagle Lake FO boundary
(Sequin 2004, p. 8).
Larrucea and Brussard (2008a, pp. 692, 694-695), surveyed locations
in Nevada and California between 2003 and 2006 which includes
information reported in Sequin (2004). In California, active sites were
found in Mono County, but not in Modoc or Lassen Counties (Larrucea and
Brussard 2008a, p. 694). This area is on the edge of the pygmy rabbit's
western range (Larrucea and Brussard 2008a, p. 694). It is possible
that pygmy rabbits have been extirpated from Modoc and Lassen Counties.
A range contraction would be more expected in a peripheral area, such
as northern California, if it were to occur
[[Page 60528]]
(Larrucea and Brussard 2008a, p. 696). The Mono County populations may
be isolated from other known populations because they appear to be
separated by a distance of approximately 100 mi (162 km) from the
nearest known populations in Nevada (Larrucea and Brussard 2008a,
p.694). These pygmy rabbit populations may have become isolated from
more eastern populations at the end of the Pleistocene (Grayson 2006,
pp. 2969-2970).
There are only a few historical (1999 and earlier) records for
California which included Modoc, Lassen, and Mono Counties. Current
information (2000 and later) indicates that while pygmy rabbit activity
continues to occur in Mono County, pygmy rabbits may have been
extirpated from both Modoc and Lassen Counties in northeastern
California. Due to limited survey efforts in northern California
overall, uncertainty remains whether this contraction has actually
occurred. Therefore, Figure 1 does not depict this possible range
contraction.
Nevada
The earliest pygmy rabbit records for Nevada include a collection
of 12 pygmy rabbits from Paradise, Humboldt County, Nevada in 1908 and
1909 (Nelson 1909, p. 278). Nelson also indicated he examined 23
additional specimens from Halleck, Ione Valley, Monitor Valley, Reese
River, and Skelton, Nevada.
Hall (1946, p. 618) indicates he examined 56 pygmy rabbit specimens
and sight records from several locations throughout the State. The
years of these collections and sightings are not included but were
recorded for the following eight counties: Washoe, Humboldt, Pershing,
Churchill, Lander, Nye, Elko, and White Pine. The range map for Nevada
also included Eureka County and a portion of Lincoln County (Hall 1946,
p. 615).
During 1993 and 1994, surveys were conducted on Sheldon National
Wildlife Refuge lands located in Washoe and Humboldt Counties. Twenty-
four surveys were completed; 17 locations were found to be occupied by
pygmy rabbits (Service 1995, p. 1). In 2002, surveys were conducted on
the refuge and locations reported in 1993 and 1994 were also revisited
(Service 2004, p. 1). In total, 41 sites were surveyed for pygmy
rabbits and 18 had pygmy rabbit sign of which 15 sites were confirmed
with photography (Service 2004, p.2). Ten of the sites from the mid
1990's had pygmy rabbit sign in 2003. Fifteen new sites were surveyed
in 2003; eight of these showed pygmy rabbits and/or their sign (Service
2004, p. 2).
Marriott (2005, p. 4) reported conducting surveys for pygmy rabbits
in all or portions of 23 units on the Ruby Lakes National Wildlife
Refuge and an area immediately adjacent to refuge lands, located in
Elko and White Pine Counties in 2004 and 2005. Evidence of pygmy
rabbits was found in seven units. The populations reported by Ports and
Ports (1989, p. 127) were found in the sand dune area adjacent to two
of the refuge units (Marriott (2005, p. 4). It was confirmed that at
least 27 burrows were active (Marriott (2005, p. 4). Three pygmy
rabbits were observed (Marriott 2005, p. 5). The surveyors were
confident that they had not found all the burrow systems within the
refuge boundaries (Marriott 2005, p. 7). They also suspected that more
pygmy rabbits occur in the sand dune area as they were unable to survey
the entire area (Marriott 2005, p. 8). In 2006, Wienke (2006) reported
conducting pygmy rabbit surveys in two areas of the Ruby Lakes National
Wildlife Refuge and adjacent BLM lands. The sand dune area survey found
44 pygmy rabbit burrow systems of which 20 appeared to be active
(Wienke 2006, p. 2). Three pygmy rabbits were observed (Wienke 2006, p.
2). In the Unit II-D area, 162 burrow systems were found; 53 were
active (Wienke 2006, p. 2). Ten pygmy rabbits were observed (Wienke
2006, p. 2).
Etzelmiller (2003, p. 1) conducted 33 survey transects in
northwestern Nye County, Nevada in 2003 and 10 showed evidence of pygmy
rabbit sign. Pygmy rabbits appear to be concentrated in Indian, Eastern
Ione, and Upper Reese River Valleys (Etzelmiller 2003, p. 3).
In 2003 Himes and Drohan (2007) surveyed for pygmy rabbits in White
Pine, Lincoln, and Nye Counties in eastern and central Nevada. Pygmy
rabbit sign (individuals, burrow, pellets) was found along 261 of 642
transects (40.7 percent) walked (pygmy rabbits and/or fresh burrows and
pellets on 89 transects (13.9 percent); fresh pellets only on 33
transects (5.1 percent); old burrows and pellets on 113 transects (17.6
percent); old pellets only on 26 transects (4.0 percent)). No sign was
observed on 381 transects (59.3 percent) (Himes and Drohan 2007, p.
376). The southern limit of the previously known record in Nevada was
extended by about 7.5 mi (12 km) south (Himes and Drohan 2007, p. 376).
All transects where pygmy rabbits and/or sign of pygmy rabbit presence
were observed in the study area were considered new locations. Due to
the extreme remoteness and fairly inaccessible terrain in the survey
area, additional localities are almost certain to remain undocumented
(Himes and Drohan (2007, p. 380).
During surveys conducted between 2003 and 2006, a total of 1,474
locations were surveyed in Nevada and California (Larrucea and Brussard
2008a, pp. 692, 694-695). Pygmy rabbits were documented at 258 sites
(Larrucea and Brussard 2008a, p. 694). The current distribution of
active sites in Nevada is similar to the historical distribution
(Larrucea and Brussard 2008a, p. 694). Active sites were found
throughout the historical range (Larrucea and Brussard 2008a, pp. 694-
695). Positive (confirmed) locations for pygmy rabbits in Larrucea
(2007) should be considered as minimum occurrence because it occurred
on a large, state-wide basis (Larrucea 2007, p. 28). Information from
Larrucea (2006) was incorporated into the Larrucea (2007) study.
Associated with the previous study (Larrucea 2007), Larrucea and
Brussard (2008b, p. 1638) revisited 105 sites based on 118 historical
records from Nevada (109) and California (9) dated between 1877 and
1946 for current pygmy rabbit presence. Pygmy rabbits were found to be
present at 36 percent of the historical sites (Larrucea and Brussard
2008b, p. 1638). When a radius (buffer) around a positive location was
increased to 3.1 mi (5 km) around a historical site, positive locations
increased to 48 percent, and when a radius of positive location was
increased to 6.2 mi (10 km) around a site, positive locations increased
to 60 percent (Larrucea 2007, p. 56). As indicated in Larrucea and
Brussard (2008a) many additional sites were found throughout the
historical range.
The Southern Nevada Water Authority (2007, p. 5) conducted pygmy
rabbit surveys in 2005 and 2006 in Dry Lake, Cave, Lake, and Hamlin
Valleys in Lincoln County and Spring, Snake, and Steptoe Valleys in
White Pine County, Nevada. Fifty-six locations were surveyed and 15 had
pygmy rabbit sign (SNWA 2007, p. 5). There was one confirmed and one
potential pygmy rabbit sightings observed (SNWA 2007, p. 5). Pygmy
rabbit sign occurred in Cave, Dry Lake, and Lake Valleys, Lincoln
County and Spring Valley, White Pine County (SNWA 2007, pp. 5-10).
Most of the historical records (1999 and earlier) for Nevada
document occurrences in the following counties: Elko, Eureka, Lander,
White Pine, and Nye Counties. There are fewer records from Washoe,
Humboldt, Pershing, and Churchill Counties. Current information (2000
and later) indicates all of these counties, with the exception of
Pershing County, continue to support pygmy
[[Page 60529]]
rabbit activity, and across a broader area within those counties than
historically noted. Pershing County is an exception because we are
unaware of any recent survey efforts being conducted in the County, and
therefore do not know if pygmy rabbits continue to exist there. In
addition, pygmy rabbit activity has been found in Lincoln County. The
recent survey efforts have located populations over a greater area
within the State and the expansion of the known range has occurred most
notably in Washoe, Lincoln, and Nye Counties.
Utah
Early reports of pygmy rabbits occurring in Utah include the first
reporting in 1932 after having been detected in 1931 (Stanford 1932,
cited in Oliver 2004, p. 14). Janson (1940, p. 6) collected pygmy
rabbits from Blue Creek Hills 10 miles (16.1 km) west of Tremonton and
in Iron County about 5 miles (8 km) west of Cedar City. He observed
them in the valley bottom west of Parowan. Anecdotal reports to Janson
indicated that pygmy rabbits occurred at the foot of Lake Mountains
west of Utah Lake. Janson (1940, p. 6) thought it was ``probable'' the
pygmy rabbit occurred in ``a more or less broken strip through the
Upper Sonoran sagebrush areas of western Utah from the northern
boundary of the State nearly to the Iron-Washington County line
southwest of Cedar City.'' In 1946, Janson (1946, p. 32) wrote that the
pygmy rabbit ``appears'' to extend through Utah west of the Wasatch
Mountains from the Idaho border to the northern border of Washington
County. He reported specimens had been collected near Clarkston, Cache
County; Blue Spring Hills and Grouse Creek, Boxelder County; and near
Modena, Lund, Kanarraville, and Cedar City, Iron County. Pygmy rabbits
or their sign had been observed near Snowville, Lucin, and Promontory,
Boxelder County; and Parowan, Iron County. He mentioned a reliable
report of their presence west of Utah Lake, Utah County, and a
questionable report west of Trout Creek (county unknown). Schantz
(1947, p. 187) noted, based on three specimens collected by Janson in
1938, a 270 mile (434.4 km) southern expansion of known pygmy rabbit
distribution in Utah from Promontory, Boxelder County, to Cedar City,
Iron County.
Janson (1946, p. 84) reported that in the winter of 1946, pygmy
rabbits appeared to be more scarce than in 1941 based on two study
areas in Utah (near Cedar City, Iron County; near Tremonton, Box Elder
County). Areas where he considered pygmy rabbits common in Utah in 1941
were found to have no pygmy rabbits occupying them in 1946.
Durrant (1952, p. 88) reported that the pygmy rabbit range in Utah
included Boxelder, Cache and Iron Counties and ``probably'' occurred
between areas along the eastern margin of Pleistocene Lake Bonneville.
He also listed additional records provided by Janson (1946, pp. 32-33)
and included Juab County (Durrant 1952, p. 89).
Holt (1975, p. 131) indicated considerable information was obtained
that altered the distributional range of the species. Populations from
Sevier River tributaries and surrounding areas indicated that the pygmy
rabbit was not restricted to the Upper Sonoran life zone (Holt 1975, p.
132). Holt (1975, pp. 136-138) indicated additional specimens have been
examined from Boxelder, Tooele, Millard, Sevier, Beaver, Piute,
Garfield, and Washington Counties. These are in addition to Janson's
(1946, pp. 32-33) records or sightings from Boxelder, Cache, Utah,
Juab, and Iron Counties.
Pritchett et al. (1987, p. 231) reported pygmy rabbit records
outside of the published range in the Bonneville Basin. One record is
near Panguitch, Garfield County (Stephenson 1966, cited in Pritchett et
al. 1987, p. 231). They mention Holt's (1975, p. 137) record of a
population south of Fish Lake on Parker Mountain and a collection and
sighting of pygmy rabbits south of Fish Lake Ranger Station and west of
Loa, Wayne County. In addition, Pritchett et al. (1987, p. 231)
reported collecting six live individuals and two skulls from the Parker
Mountain region of the Awapa Plateau, Wayne County. The Awapa Plateau
is part of the Fremont River watershed and is outside of the
Pleistocene Lake Bonneville drainage. During 1986, Pritchett et al.
(1987, p. 233) looked for pygmy rabbits or their sign and were able to
find evidence from Burrville, about 0.5 mi (0.8 km) northwest of Parker
Mountains, south through Grass Valley to north of Otter Creek
Reservoir. They were unable to find Holt's (1975, p. 137) population
west of Otter Creek Reservoir Pritchett et al. (1987, p. 233). They
wrote that the valley between Kingston and Otter Creek is narrow and
disturbed. They found no evidence of pygmy rabbits from Sigurd to
Burrville or through Emery Valley.
Based on the two previous study areas in Utah between 1938 and
1946, and limited observations in Utah (near Clarkston, Cache County;
near Snowville and Grouse Creek, Box Elder County) in 2001, Janson
(2002, p. 32) wrote that recent information indicated pygmy rabbit
populations had declined in some areas where they were previously more
abundant, mostly as a result of human actions. He states that
residential and commercial development, farming, and range improvements
for grazing, especially near Cedar City, had impacted the sagebrush
habitat. He found no recent sign of occupancy near Cedar City, Utah.
Oliver (2004 pp. 16-18) provides a review of pygmy rabbit in Utah
and lists location records for the pygmy rabbit between 1946 and 2003
which includes the following 14 counties: Washington, Boxelder,
Garfield, Piute, Iron, Sevier, Cache, Beaver, Rich, Wayne, Toole,
Millard, Juab, and Utah.
In 2005, Welch (2005, pp. 15-17, 36) conducted walking surveys of
48 big sagebrush stands or sites in Utah (41 sites in Box Elder, Rich,
Tooele, Davis, Utah, Wasatch, Duchesne, Uintah, Juab, Carbon, Sevier,
Beaver, Piute, Wayne, Iron, and Washington Counties), Idaho (4 sites in
Cassia and Oneida Counties), and Nevada (3 sites in Elko and White Pine
Counties) in 2003 and 2004. Twelve of these sites were known to have
supported pygmy rabbits in the past, 26 possibly supported pygmy
rabbits in the past, and 10 sites had no record of past use (Welch
2005, p 2). Of the 12 sites known to have supported pygmy rabbits in
the past, 4 were found to support pygmy rabbits or current sign (Cassia
County, Idaho; Piute and Rich Counties, Utah; Elko County, Nevada); of
the 26 possible historical sites, 1 was found to support current pygmy
rabbit activity during his study (Iron County, Utah) (Welch 2005, pp.
9, 14-17, 36). In addition, he surveyed 13 other sites previously
listed by Janson (2002, pp. 10-11) (Welch 2005, p 2). Of these 13
sites, none showed signs of current use; only 5 had some remaining
suitable habitat (Welch 2005, p 10).
Flinders et al. (2005, p. 7) surveyed habitat in Grass Valley in
Piute, Sevier, and Wayne Counties located in south central Utah. Pygmy
rabbit surveys were conducted in areas slated for sagebrush treatment
but where pygmy rabbit surveys had not been previously conducted as
well as revisiting areas where pretreatment pygmy rabbit surveys had
been completed by BLM employees (Flinders et al. 2005, p. 13).
According to Flinders et al. (2005, p. 13), BLM surveys identified 118
active burrow systems and 85 inactive ones. Flinders et al. (2005, p.
13) found 14 locations with active burrow systems and all others found
in treatment areas were determined to be inactive.
During 2005 and 2006, Larsen et al. (2006) surveyed for pygmy
rabbits in Deep Creek watershed, Tooele County.
[[Page 60530]]
This watershed is located on the Utah-Nevada border and the closest
known extant pygmy rabbit population in Nevada occurs about 52 miles
(84 km) to the northwest (Larsen et al. 2006, p. 4). The Nevada
population had been surveyed within the past 5 years (Larsen et al.
2006, p. 4). Four historical (1905-2002) sites showed no evidence of
present occupation by pygmy rabbits (Larsen et al. 2006, p. 5). In
addition, three active pygmy rabbit locations (confirmed with
photography) and three inactive ones were found within the watershed
(Larsen et al. 2006, pp. 5-6). Pygmy rabbits were not photographed at
the inactive sites and fresh pellets were lacking; however, given the
recent activity and the potential for reoccupation, the authors
believed these inactive sites are important to the species in the
watershed (Larsen et al. 2006, p. 15). Interestingly, based on the map
provided by Larsen et al. (2006, p. 16), the three inactive sites and
the three active sites are located north and south of the historical
sites, respectively.
Flinders (2007, pp. 2-3) indicates discovery of fairly extensive
populations in Hamlin Valley located on the Utah-Nevada border in Iron
and Beaver Counties. Numerous burrows systems classified as current or
recently current have been found in the area. This area may provide a
corridor between Utah and Nevada pygmy rabbit populations. Pygmy rabbit
use was found on both sides of the border.
In summary, most historical records (1999 and earlier) for Utah
occurred in the following six counties: Boxelder, Iron, Washington,
Garfield, Piute, and Wayne Counties. Fewer records occurred in Beaver,
Millard, Juab, Tooele, Sevier, Utah, Rich, and Cache Counties. Current
information (2000 and later) indicates Boxelder, Tooele, Beaver, Iron,
Washington, Garfield, Piute, Wayne, Sevier, and Rich Counties continue
to support pygmy rabbit activity. Current pygmy rabbit activity is
uncertain in Cache, Utah, and Juab because we are unaware of any recent
survey efforts occurring in these counties. A new area in Millard
County was searched in 2003 and activity was not observed. The recent
survey efforts have located active population in Sanpete County and in
additional areas previously unknown within the other counties where
surveys have occurred.
Abundance
We are unaware of any historical or current population estimates
being made for the pygmy rabbit by individual States or for the range
considered in this finding. Any figures related to numbers of pygmy
rabbits provided in the literature have been reported as individuals
collected (Dice 1926 p. 27 (10 in Oregon); Grinnell et al. 1930, pp.
553-554 (20 in California), p. 555 (35 in Nevada); Bailey 1936, p. 111
(8 in Oregon); Severaid 1950, p. 2 (4 in California); Borell and Ellis
1934, pp. 41-42 (7 in Nevada)), or individuals observed (Grinnell et
al. 1930, p. 553 (1 in California); Bailey 1936, p. 111 (40 in Oregon);
Jones 1957, p. 274 (1 in California); Bartels 2003, p. 88 (5 in
Oregon); Rachlow and Witham 2004a, p. 3 (20 in Idaho); Flinders et al.
2005 p. 45 (250 in Utah)), or individuals photographed (Flinders et al.
2005 p. 45 (241 in Utah)) or individuals live trapped (Rauscher 1997,
p. 9 (58 in Montana); Rachlow and Witham 2004a, p. 3 (25 in Idaho);
Crawford 2008, p. 22 (337 in Nevada and Oregon)), or mortalities
reported related to study efforts (Rauscher 1997, p. 9 (11 in Montana))
in various parts of its range by researchers.
Other authors used qualifying statements to indicate abundance
(Anthony 1913, p. 22, in Oregon wrote, ``On account of the thick growth
and the animal's habit of circling about under cover an accurate count
of the inhabitants of such a locality was difficult to obtain.''
Anthony (1913, p. 21) also stated that the species was ``not uncommon''
around Ironside, Malheur County, Oregon; Bailey (1936, p. 111) stated
that Oregon pygmy rabbits are locally abundant only where conditions
are favorable. Janson (1940, p. 41) wrote that pygmy rabbits in Utah
occur in scattered communities which are limited by characteristics
favorable to the pygmy rabbit. In these areas where characteristics
favorable to the pygmy rabbit are found, the pygmy rabbit may be quite
abundant.
Under the species description provided above, several researchers
have reported a variety of density estimates for pygmy rabbits on
individual sites. However, the number of active burrows may not be
directly related to the number of individuals in a given area because
some individual pygmy rabbits appear to maintain multiple burrows,
while some individual burrows are used by multiple individuals (Janson
1940, pp. 21, 29; Janson 1946, p. 44; Gahr 1993, pp. 66, 68; Heady
1998, p. 25). It is not appropriate to extrapolate any of these
reported densities beyond the local scale due to the patchy
distribution of suitable habitat and the variable amount of habitat
actually occupied (Keinath and McGee 2004, p. 20). Efforts to model the
amount and distribution of suitable habitat have met with minimal
success and are useful mainly for focusing future survey efforts
(Keinath and McGee 2004, p. 20).
More recently, attempts have been made to estimate pygmy rabbit
abundance by different methods. Rachlow and Witham (2004b, pp. 2-13) in
Idaho evaluated several census techniques for pygmy rabbits (thermal
imagery, burrow surveys, live trapping, line transect surveys, fecal
pellet counts). They found several techniques were infeasible due to
cost or the likelihood of providing imprecise estimates. Surveys of
burrow systems provide an obtainable index of activity, but more work
is needed to associate this index with population density estimates
(Rachlow and Witham 2004b, p. 13). Price (2008, p. 2) in Idaho is
attempting to develop a standardized method to monitor abundance of
pygmy rabbits. Price is attempting to calibrate an index of abundance
based on burrow systems by correlating the index with estimates of
population density. Sanchez (2007, p. 108) states that tools used for
estimating relative abundance of pygmy rabbits rely on locating and
assessing burrows and fecal pellets. Sanchez evaluated the temporal
changes in fecal pellets and burrow systems to assess their potential
usefulness as indicators of relative abundance of pygmy rabbits
(Sanchez et al. 2009, p. 427). The persistence and detectability of
pellets and burrows over time may be influenced by factors such as
weather, soil microorganisms, invertebrates, vertebrates, vegetative
growth, or the soil's susceptibility to slumping or compaction (Sanchez
et al. 2009, p. 427). Sanchez et al. (2009) determined that next to
actual sightings of pygmy rabbits, burrow systems and pellets are the
most reliable evidence of pygmy rabbit presence in an area; together
they may provide an indirect index of population trend but depend on
the objectives of the investigator as multiple factors can affect
changes in pellets and burrows over time (Sanchez et al. 2009, p. 433).
Therefore, reliably estimating the abundance of pygmy rabbits on a
statewide or range wide basis is not currently possible.
Trend
Population trends are normally defined in terms of distribution or
abundance. In the case of the pygmy rabbit, the available scientific
information does not allow for an analysis of abundance over time.
Abundance trends for the pygmy rabbit in each State and throughout its
range are unknown and how impacts to the sagebrush habitat from various
events or actions have affected pygmy rabbit abundance remain unclear.
[[Page 60531]]
Distribution information obtained from early literature and records
represent a collection of sightings documented by different individuals
over time. These early records were not collected in a systematic,
comprehensive manner with the goal of determining the pygmy rabbit's
distribution. However, they do reflect the species historical
distribution known or suggested at that time, which was modified as
previously unknown locations were found. Our understanding of the
distributional trend throughout the species' range has improved only
recently.
Surveys have concentrated on documenting populations within a
particular State by revisiting historical sites and looking for
previously unknown sites. It is important to understand that
considering only contemporary surveys of historical sites is likely to
result in an apparent loss of a species from any number of locations
regardless of whether the species has suffered a decline in numbers or
not (Shaffer et al. 1998, cited in Larrucea and Brussard 2008b, p.
1639). Populations naturally fluctuate locally so some historical sites
are expected to disappear due to chance alone (Hanski 1991, cited in
Larrucea and Brussard 2008b, p. 1639). In addition, it is often
difficult to determine whether pygmy rabbit activity continues in a
particular area because many historical site descriptions are vague.
With the possible exception of California and Nevada, recent survey
efforts have not been comprehensive in individual States. Due to
funding limitations, various individuals from various agencies have
selected different areas in each State to survey. As a result,
different methodologies were developed for these surveys. Some
individual sites or locations have been destroyed while some
populations may have relocated to other areas across the landscape
because of various factors. Appropriately, surveys have also expanded
into new areas and have found previously undocumented pygmy rabbit
populations. These efforts have improved our understanding of the
species' current distribution across its range. Because of the emphasis
in determining where pygmy rabbits occur on the landscape, monitoring
of known sites over time has essentially not occurred for pygmy rabbit
populations.
Historical records provide no information on the amount of area
where pygmy rabbits were collected or observed. Rarely do recent survey
efforts report the amount of acreage attributed to occupied or
unoccupied pygmy rabbit burrow systems. Therefore, we are unable to
compare changes in the amount of acres used historically or currently
by pygmy rabbits.
Because of this lack of long-term distributional data, we have
compared active and inactive (occupied versus unoccupied) records in
the Service's databases from 1877 to 1999 to active and inactive
records from 2000 to 2008. Based on a comparison of these two groups of
records, the distribution of pygmy rabbits is quite similar to our
understanding of the historical range in all States except California
as discussed in more detail above. Not only do pygmy rabbits continue
to occupy the general areas previously known, new areas of current
activity have been documented due to increased survey efforts in recent
years. We are encouraged by recent survey efforts and that researchers
continue to find populations where they occurred historically. These
survey efforts have also lead to the discovery of active areas in
previously unknown or undocumented locations, and assist in improving
our understanding of the distribution of the pygmy rabbit across its
range.
In some States (Montana, Nevada, and most notably Wyoming) these
increased survey efforts have led to an extension of the current
distribution of pygmy rabbits within these States. We are not
suggesting that these populations have expanded in these States, only
that increased survey efforts have located previously unknown or
undocumented populations of this species. It appears that recent survey
efforts have not occurred in the peripheral counties in Oregon so we
are unsure of current pygmy rabbit activity in these areas. Idaho also
shows some uncertainties because of some inactive areas and we are
unaware of previous areas being revisited; however, active areas have
also been found in previously unknown areas and counties. Utah shows
some uncertainties because we are unaware of previous areas being
revisited. Active areas have been found in previously unknown areas and
counties in Utah. It is possible that California has experienced a
relatively small range contraction in the northeast in Modoc and Lassen
Counties. Because we eliminated undesirable records from our analysis,
as explained above, we believe we have presented a conservative look at
our current understanding of the distribution of the pygmy rabbit
across its range. The pygmy rabbit not only occurs generally throughout
its historical range, it also occurs in previously unknown or
undocumented areas, thus increasing our understanding of the species'
current distribution.
Habitat
Sagebrush is the most widespread vegetation in the western United
States' intermountain lowlands (West and Young 2000, p. 259). A number
of species and subspecies of sagebrush are recognized (Connelly et al.
2004, p. 5-2) and each has unique habitat requirements and responses to
disturbances (West and Young 2000, pp. 259-261). Sagebrush species and
subspecies occur in areas dictated by local soil type, soil moisture,
and climatic conditions (West 1983, pp. 333, 355-357; West and Young
2000, pp. 259-261). The degree of dominance by sagebrush varies with
local site conditions and disturbance history. Plant associations,
typically defined by perennial grasses, further describe distinctive
sagebrush communities (Miller and Eddleman 2001, p. 14; Connelly et al.
2004, p. 5-3) and are influenced by soil type, elevation, topography,
and precipitation.
Sagebrush species are long-lived with some surviving to 100 years
(West and Young 2000, p. 259). Allelopathic chemicals are produced that
reduce seed germination, seedling growth and root respiration of
competing plant species and inhibit the activity of soil microbes and
nitrogen fixation. Sagebrush species are resistant to environmental
extremes, with the exception of fire and on occasion defoliating
insects (West 1983, p. 341). Most species of sagebrush are killed by
fire (Miller and Eddleman 2001, p. 17; West and Young 2000, p. 259).
The natural re-colonization of sagebrush in burned areas depends on the
presence of adjacent live plants for a seed source or on a seed bank,
if present (Miller and Eddleman 2001, p. 17).
Sagebrush species are typically divided into two groups, tall
sagebrush (also known as ``big'') and low sagebrush, based on their
affinities for different soil types (West and Young 2000, p. 259).
Within tall sagebrush, there are three subspecies, Artemesia tridentata
ssp. wyomingensis (Wyoming big sagebrush), A. t. ssp. tridentata (basin
big sagebrush), and A. t. ssp. vaseyana (mountain big sagebrush) which
are the most widely distributed (Knick et al. 2003, p. 614). There are
two primary species in the low sagebrush group: A. arbuscula (low
sagebrush) and A. nova (black sagebrush) (Knick et al. 2003, p. 614).
Big sagebrush occurs in coarse-textured and/or well drained sediments,
while low sagebrush typically occurs where erosion has exposed clay or
calcified soil horizons (West and Young 2000, p. 261). Big sagebrush
will die if saturated long
[[Page 60532]]
enough to create anaerobic conditions for 2 to 3 days (West and Young
2000, p. 259). Some low sagebrush species are more tolerant of
occasionally supersaturated soils, and many low sagebrush sites are
partially flooded during spring snowmelt. Sagebrush species do not
tolerate high salinity soils (West and Young 2000, p. 270).
Sagebrush and sagebrush ecosystem response to natural and human
influenced disturbances varies based on the sagebrush species and its
understory, as well as abiotic factors such as soil type and
precipitation. Mountain big sagebrush, for example, generally can
recover more quickly and robustly than Wyoming big sagebrush following
a disturbance (Miller and Eddleman 2001, p. 22) likely due to its
occurrence on moist, well drained soils as compared to the very dry
soils typical of Wyoming big sagebrush communities. Soil associations
have resulted in disproportionate levels of habitat conversion across
different sagebrush communities. Basin big sagebrush occurs at lower
elevations, in soils that retain moisture two to four weeks longer than
in well drained, but dry and higher elevation soils typically occupied
by Wyoming big sagebrush. As a result, sagebrush communities dominated
by basin big sagebrush have been converted to agriculture more
extensively than communities found on poorer soils (Winward 2004, cited
in 70 FR 2254). The effects of disturbance on sagebrush species are not
constant across their range.
Within the sagebrush ecosystem, there are two primary features of
pygmy rabbit habitat: relatively taller and denser big sagebrush and
deep soils (Ulmschneider et al. 2004, p. 2). Pygmy rabbit burrows are
usually found in the taller and denser sagebrush within an area. The
height of the sagebrush can vary greatly, from approximately 1.5 to 7
ft (0.46 to 2.1 m). Sagebrush density can also vary, but it is common
that the sagebrush canopy cover at burrows is greater than 30 percent
(within a 20-ft (6.1 m) radius of burrow) (Ulmschneider et al. 2004,
pp. 2, 23). Occupied habitat includes various subspecies of sagebrush,
including Wyoming, mountain, and basin. Other shrub species may also be
present, including Purshia tridentata (bitterbrush), rabbit brush,
Sarcobatus vermiculatus (greasewood), Symphoricarpos spp. (snowberry),
and Juniperus spp. (juniper). In Oregon and Nevada, some areas occupied
by pygmy rabbits include rabbit brush as dominant or co-dominant with
sagebrush and burrows have been found under large, dense rabbit brush
and greasewood (Ulmschneider et al. 2004, p. 2).
Pygmy rabbits can also occupy habitat that does not appear ideal.
These areas include sagebrush that is short in height and ``bad'' soil.
In east central Idaho, pygmy rabbits occupy ``mima mounds'' (mounds of
soil several feet (ft) high and approximately 20 to 30 ft (6.1 to 9.1
m) in diameter) with taller and denser sagebrush dotted in a landscape
of shorter and thinner sagebrush. In Montana, the average sagebrush
height in occupied sites can be about 15 in (38.1 cm). In Montana,
pygmy rabbits have been found in areas where the sagebrush is not very
dense and is about 30 in (76.2 cm) high, especially in mountain bowls
and where sagebrush has been manipulated. In Utah, pygmy rabbits have
been found to occupy 12 to 120-inch (30.5 to 304.8 cm) tall sagebrush.
Regardless of the absolute height of the vegetation, pygmy rabbits will
almost always burrow in the tallest and densest sagebrush on the
landscape (Ulmschneider et al. 2004, pp. 2-3).
Generally, pygmy rabbits burrow in loamy soils deeper than 20 in
(50.8 cm). Soil composition needs to be soft enough for digging, yet be
able to support a burrow system. In southwest Idaho, pygmy rabbits
occur in areas with soils classified as stony sandy loam, and sandy
loam over sandy clay and clay loam. In east central Idaho, soils are
gravelly outwash plains with lime-coated rocks. On the lava plains of
southeast Idaho, rabbits will often burrow between or under lava
boulders. In Nevada, soils are light-colored and friable (easily
crumbled) (Ulmschneider et al. 2004, p. 3).
Occupied pygmy rabbit habitats in Oregon are very similar to those
in Idaho (below). Most habitat occurs where big sagebrush inclusions
are mixed with low sagebrush, rabbit brush, or shorter stature big
sagebrush. Mounding similar to ``mima mounding'' occurs in most of
these sites. Sagebrush on the mounds is usually 1 to 3 ft (0.30 to 0.91
m) taller than those in the surrounding area. Another common type of
occupied habitat in Oregon is small draw bottoms where deeper soils
have collected. Most of these sites are vegetated with basin big
sagebrush in the drainage bottom, surrounded by Wyoming big sagebrush,
low sagebrush, or mountain big sagebrush in the surrounding uplands.
Some areas utilized by pygmy rabbits are dominated by rabbit brush.
Some soil mounding can occur in these areas, but can be subtle. Burrows
in these areas seem to be restricted to the very bottom of the
drainages or the lower inside slopes of the drainage (Ulmschneider et
al. 2004, p. 4).
In Oregon, Weiss and Verts (1984, p. 567) found mean shrub cover in
areas occupied by pygmy rabbits was about 29 percent and mean shrub
height was about 33.1 in (84 cm). Mean shrub cover best distinguished
occupied sites from adjacent sites (29 versus 18 percent), followed by
mean soil depth (51 versus 31 cm), and mean shrub height (84 versus 53
cm). Percent basal area of perennial grasses, density of annual
grasses, density of forbs, and components of soil texture were found to
contribute little to the difference between occupied areas and adjacent
sites. Meisel (2006, p. 21) found average sagebrush height 2.1 ft (0.65
m) and percent sand content in the soil (50.2 percent) as the two
variables that determined occupied burrows. Unoccupied burrows had an
average sagebrush height of 1.0 ft (0.32 m) and 45.5 percent sand in
the soil sample.
In Idaho, pygmy rabbits are found in mima mound areas. In the
Salmon, Idaho area, pygmy rabbits are found on alluvial plains dotted
with mounds about 20 to 30 ft (6.1 to 9.1 m) in diameter, 1 to 2 ft
(0.3 to 0.61 m) tall, several hundred ft or yd apart, where the
sagebrush is taller than in the surrounding inter mound spaces. In
southwest Idaho, a similar habitat is occupied by pygmy rabbits where
big sagebrush islands are intermingled with low sagebrush. In the
Owyhees of southwest Idaho, pygmy rabbits are found in swales of taller
sagebrush. Soil mounding is present, but it does not form distinctive
mima mounds. In the Bruneau Plateau, pygmy rabbits are found in the
bottoms and lower slopes of small drainages where the sagebrush is
denser and taller, indicating deeper soils (Ulmschneider et al. (2004,
p.3). In the Owyhees of southwestern Idaho, Burak (2006, pp. 63-64)
found occupied pygmy rabbit areas had significantly greater total
shrub, sagebrush (A. t. ssp. vaseyana), forbs, and litter cover, and
significantly less bare soil and rock than in unoccupied areas. Total
shrub, sagebrush (A. t. ssp. vaseyana) and snowberry cover was greater
in occupied pygmy rabbit habitat. Height of total shrubs and sagebrush
was also significantly higher in occupied areas. Total shrub cover
values ranged from 41 to 67 percent. Sagebrush cover values ranged from
12 to 60 percent. These differences in total shrub cover and sagebrush
cover suggest that total shrub cover does not need to be comprised of
sagebrush primarily. It is unknown what minimum amount of sagebrush
cover is needed for pygmy rabbit survival. Burak (2006, p. 65) found in
his study areas
[[Page 60533]]
average total shrub and sagebrush height to be 160 in (63 cm) and 167.6
in (66 cm), respectively.
Pygmy rabbits in Montana are found in habitats similar to those in
Idaho and Oregon- large intermountain valley bottoms, alluvial fans,
mountain valleys and bowls, drainage bottoms, plateaus, rolling
sagebrush plains and isolated patches of sagebrush in grasslands.
Preferred habitat in Montana appears to be gently sloping or nearly
level floodplains where adequate sagebrush and appropriate soils exist.
However, many occupied sites have marginal sagebrush cover and
shallower soils. If pygmy rabbits are found in areas containing mima-
like mounds, they generally occur throughout the continuous sagebrush
coverage at varying densities and into sagebrush drainages
(Ulmschneider et al. 2004, p. 4).
In Wyoming, pygmy rabbits occur in swales of taller, denser
sagebrush in a setting of hillsides with thinly distributed, shorter
sagebrush. The general areas used by pygmy rabbits have evenly
distributed, taller, and more structurally diverse sagebrush with a
dense canopy. Three subspecies of big sagebrush can be present, basin,
Wyoming, and mountain (Ulmschneider et al. 2004, p. 5). In Wyoming,
Purcell (2006, p. 62) found that the proportion of bare ground and
shrub cover may influence habitat features used by pygmy rabbits. Of
the 10 study areas, 6 had significantly less bare ground at use sites
than at non-use sites. Six of the 10 study areas had significantly
greater shrub cover at use sites compared with non-use sites. Although
sagebrush was the dominant shrub in all study areas, other shrubs
contributed to the shrub cover. In relation to soils, Purcell (2006,
pp. 64-65) found 8 of the 10 study areas showed a higher fine fraction
of soil in both the surface and subsurface levels at use sites. The
amount of coarse material in the soil may not inhibit digging if the
soil is soft. Both surface and subsurface samples indicated that softer
soils occurred at the use sites compared with the non-use sites. There
did not appear to be a relationship between soil texture and areas used
by pygmy rabbits (Purcell 2006, p. 65).
Western EcoSystems Technology, Inc. (2008, pp. 18, 20, 22-23) found
the dominant habitat types within 6.6 ft (2 m) of pygmy rabbit burrows
along three pipeline routes in 2007 were tall sagebrush (42 percent),
low sagebrush (48 percent), and desert scrub (10 percent). The average
percent of different shrub types located within 16 ft (5 m) of pygmy
rabbit burrows along two of the pipeline routes in 2006 indicated tall
sagebrush at 56.6 percent, low sagebrush at 34.7 percent, and
greasewood at 7.7 percent. Average percentages of shrub cover within
6.6 ft (2 m) of burrows along the three routes in 2007 show 58 percent
of burrows had between 26 and 50 percent shrub cover. Twenty-eight
percent had a shrub cover of between 11 and 25 percent. Along two of
the routes in 2006, pygmy rabbit burrows were found in 33.3 percent
loam, 30.2 percent clay, and 20.3 percent sand.
In California, pygmy rabbits occupy areas near Mono Lake in islands
of big sagebrush and loamy soils, similar to areas in Nevada, but with
sandier soils. Burrows tend to be in sandy loam soils, which are often
surrounded by very sandy soils. Near Bodie, an abandoned mining town
approximately 10 mi (16.1 km) north of Mono Lake, the habitat includes
shorter, more uniform sagebrush, often less than 3 ft (0.9 m) tall,
with less clumping of the sagebrush. Pygmy rabbit habitat in
northeastern California is very similar to habitat in adjacent Nevada
(Ulmschneider et al. 2004, p. 5).
In Nevada, pygmy rabbits are found in broad valley floors, drainage
bottoms, alluvial fans, and other areas with friable soils. Burrows can
be located in mounds (either natural or human caused) when they are
available in these types of soils. Pygmy rabbit burrows are easiest to
find in light colored, friable soils. These soils are usually found in
valley bottoms and can be associated with rabbit brush or sagebrush
vegetation. The understory of grasses and forbs can vary from almost
none to dense (Ulmschneider et al. 2004, p. 4). In California and
Nevada, Larrucea and Brussard (2008a, pp. 695-697) found mean sagebrush
cover at occupied sites was 44.7 percent. Mean sagebrush height at
occupied sites was 38.8 in (98.4 cm), but it was not found to be a
significant factor. Pygmy rabbits were more likely to occupy sites
within clusters of sagebrush located higher than the surrounding
sagebrush or in sagebrush islands. These islands occurred in a range of
surrounding sagebrush heights of 4.7 to 46.1 in (12 to 117 cm). These
islands also had greater sagebrush cover. Occupied sites were located
on loamy soils with a mean sand and clay content of 39.1 percent and
20.4 percent, respectively. Pygmy rabbits occupied sites with little or
no understory.
In Utah, site characteristics inhabited by pygmy rabbits vary
considerably, because they occupy three different ecoregions: Central
Basin and Range, Wyoming Basin, and the Wasatch and Uintah Mountain.
These ecoregions vary in latitude, elevation, precipitation, and
geologic history. Pygmy rabbits are found in the western half of the
state in alluvial deposits and in favorable micro sites on ``bench
tops''. Habitat in northern Utah is characterized by Wyoming, mountain,
and basin big sagebrush, and bitterbrush and snowberry present at the
higher elevations. Pygmy rabbit habitat in southern areas is often
limited to the bottom of gentle drainages supporting Wyoming sagebrush
with black sagebrush, Atriplex confertifolia (shadscale), and Kochia
americana (gray molly) community of minimal height (11.0 in, 28 cm)
(Ulmschneider et al. 2004, p. 5).
Evaluation of Information Pertaining to the Five Threat Factors
Section 4 of the Act (16 U.S.C. 1533) and implementing regulations
(50 CFR part 424) set forth procedures for adding species to, removing
species from, or reclassifying species on the Federal Lists of
Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of
the Act, a species may determine to be endangered or threatened on the
basis of any of the following five factors:
(A) The present or threatened destruction, modification, or
curtailment of its habitat or range;
(B) Overutilization for commercial, recreational, scientific, or
educational purposes;
(C) Disease or predation;
(D) The inadequacy of existing regulatory mechanisms; or
(E) Other natural or manmade factors affecting its continued
existence.
In making this 12-month finding, information pertaining to the
pygmy rabbit in relation to the five factors provided in section
4(a)(1) of the Act is discussed below. In making our 12-month finding
on the petition, we considered and evaluated the best scientific and
commercial information available.
In considering what factors might constitute threats to a species,
we must look beyond the exposure of the species to a factor to evaluate
whether the species may respond to the factor in a way that causes
actual impacts to the species. If there is exposure to a factor and the
species responds negatively, the factor may be a threat and we attempt
to determine how significant a threat it is. The threat is significant
if it drives, or contributes to, the risk of extinction of the species
such that the species warrants listing as endangered or threatened as
those terms are defined in the Act.
[[Page 60534]]
Factor A: The Present or Threatened Destruction, Modification, or
Curtailment of the Species' Habitat or Range
The following potential factors that may affect the habitat or
range of the pygmy rabbit are discussed in this section, including: (1)
Habitat conversion, (2) agriculture, (3) sagebrush treatment, (4)
livestock grazing, (5) nonnative invasive plants, (6) fire, (7) pinyon-
juniper woodlands encroachment, (8) urban and rural development, (9)
mining (10) energy exploration and development, (11) habitat
fragmentation, (12) habitat manipulation conducted to benefit greater
sage-grouse (Centrocercus urophasianus urophasianus), and (13)
conservation strategies and actions.
Habitat Conversion
Sagebrush once covered approximately 270 million ac (109 million
ha) in western North America within 13 States (Washington, Oregon,
Idaho, Montana, Wyoming, North and South Dakota, Colorado, New Mexico,
Arizona, Utah, Nevada and California (American Lands Alliance 2001, p.
3). Today, because of various land uses, about 150 million ac (61
million ha) of sagebrush habitat remain (American Lands Alliance 2001,
p. 3). Pygmy rabbits occur within a portion of this area, but they are
not known to occur in Arizona, Colorado, North or South Dakota, or New
Mexico. The amount of sagebrush acres suitable for supporting pygmy
rabbits is a subset of the remaining acres in the states they are known
to occur, based on the species' specific habitat needs within the range
of the sagebrush ecosystem. Therefore, the amount of suitable sagebrush
habitat for pygmy rabbits has always been less than the total amount of
sagebrush acreage distributed across western North America.
A number of activities have been identified as potentially
impacting pygmy rabbit habitat and individuals or populations across
the species' range. These activities most commonly include land
management practices which result in the direct loss of sagebrush
habitat (e.g., conversion of sagebrush habitat to agricultural
purposes, sagebrush treatment to increase forage for livestock);
livestock grazing; invasive nonnative plant species; fire; urban and
rural development; mining; energy exploration and development;
fragmentation of sagebrush habitat, and sagebrush modification for
other species such as greater sage-grouse (Roberts 2001, p. 17; Red
Willow Research Inc. 2002, pp. 58-59, 64-65; Bartels 2003, pp. 101-104;
Keinath and McGee 2004, pp. 14, 23-25; Hayden Wing Associates, Inc.
2008b, p. 1; Larrucea 2006, p. 7; Larrucea and Brussard 2008b, p.
1636).
As discussed in the background section, the pygmy rabbit is a
sagebrush obligate, but it occurs within a subset of the sagebrush
ecosystem within its range. Pygmy rabbits are found where sagebrush
cover is sufficiently tall and dense and where soils are sufficiently
deep and loose to allow burrow construction (Bailey 1936, p. 111; Green
and Flinders 1980a, p. 2; Campbell et al. 1982, p. 100; Weiss and Verts
1984, p. 563; WDFW 1995, p. 15). Thus, pygmy rabbits are not
distributed uniformly across the full range of the sagebrush shrub-
steppe ecosystem. In large areas of the sagebrush habitat, pygmy
rabbits are not known to occur, and in those areas where it does occur
it is patchily distributed. For each of the following potential threats
listed in Factor A, the available information provides general
characteristics of sagebrush habitat degradation or provides examples
of impacts in site-specific areas resulting in possible impacts to
pygmy rabbits.
Agriculture
Large-scale conversions of western rangelands to agricultural lands
began under the Homestead Acts of the 1800's (Todd and Elmore 1997,
cited in Braun 1998, p. 4). More than 70 percent of the sagebrush
shrub-steppe habitat has been converted to agricultural crops in some
States (Braun 1998, p. 2). Hironaka et al. (1983, cited in 70 FR 2255)
estimated that 99 percent of basin big sagebrush habitat in the Snake
River Plain has been converted to cropland. Across the Interior
Columbia Basin of southern Idaho, northern Utah, northern Nevada,
eastern Oregon and Washington, about 15 million ac (6 million ha) of
shrub-steppe habitat has been converted to agricultural cropland
(Altman and Homes 2000, p. 10). Development of irrigation projects to
support agricultural production also resulted in sagebrush habitat loss
(Braun 1998, p. 4). Reservoirs have been constructed to facilitate
these irrigation projects, impacting native shrub-steppe habitat
adjacent to rivers, as well as supporting the conversion of more upland
shrub-steppe habitat to agriculture. As irrigation techniques have
improved, additional land has been irrigated, and more big sagebrush
(A. tridentata) cleared. Shrub-steppe habitat continues to be converted
to dry land and irrigated cropland but at a much lower rate (Braun
1998, p. 4).
Review of current sagebrush steppe habitat and agricultural lands
within Great Basin sagebrush among states within the range of the pygmy
rabbit show that less than 10 percent is impacted by agriculture for
Oregon, Montana, Wyoming, California, Nevada and Utah. Only Idaho has a
greater percentage of agricultural lands within Great Basin sagebrush
at about 18 percent (75 FR 13925).
The loss or modification of sagebrush habitat due to agricultural
conversion and impacts to pygmy rabbits across its range could include
injury or death at the time of vegetation clearing, reduction in forage
and shelter, temporary or permanent home range abandonment, increased
habitat fragmentation, increased dispersal barriers, increased
predation, and population declines. As a sagebrush-dependent species,
complete loss of sagebrush over a large area could have long-term
impacts to pygmy rabbits. According to Roberts (1998, p. 11), of the
583,600 ac (236,180 ha) he inventoried in Lemhi and Custer Counties,
Idaho for pygmy rabbit occupancy, 122,300 ac (49,494 ha) had been
permanently removed due to agriculture conversion. However, the acreage
or percentage of land that had been occupied by pygmy rabbits is
unknown. White and Bartels (2002, pp. 7-8) believe that the pygmy
rabbit historically was impacted by sagebrush removal for agricultural
purposes in Idaho as 3 of 13 historic sites they visited were disturbed
by agriculture, and pygmy rabbit activity was not observed at these
sites.
In Utah, Pritchett et al. (1987, p. 233) reported that a portion of
the Sevier River Valley between Kingston and Otter Creek, containing
one of the last large patches of sagebrush, had been plowed. They
speculated this may previously have been a dispersal route for pygmy
rabbits from Iron County to Wayne County, Utah. Janson (2002, pp. 31-
32) reported in 2001 that he found wheat acreage had expanded in the
Blue Springs Hills of Box Elder County and that the sagebrush was
almost gone. He also stated that the foothills area near Clarkston,
Cache County had experienced increased farming activity which had
eliminated sagebrush. Larsen et al. (2006, p. 5) visited four
historical pygmy rabbit sites in Tooele County, Utah which were
unoccupied. Some of them (number not indicated) showed evidence of
conversion to farmland.
In Utah, Idaho, and Nevada, Welch (2005, p. 10) visited historical
pygmy rabbit sites in 2003 and 2004. He mentioned 7 of 13 were impacted
or likely impacted by agricultural conversion to farmland including
wheat and alfalfa fields.
[[Page 60535]]
In Montana, Rauscher (1997, p. 16) thought conversion of sagebrush
to agriculture was minimal in southwest Montana because of the large
expanses of public land. He documented that the suspected location for
one historical pygmy rabbit record had been converted to irrigated
farmland (Rauscher 1997, p. 14).
In California, Williams (1986, p. 51) indicated that loss of
sagebrush habitat in California to agriculture was less of a concern
than loss of habitat to overgrazing. Larrucea and Brussard (2008b, p.
1638) revisited 105 of 118 historical pygmy rabbit sites from Nevada
(109) and California (9) dated between 1877 and 1946 to document
current pygmy rabbit presence. They determined the presence or absence
of current land use (agricultural conversion, livestock grazing, fire,
urbanization and presence of pinyon-juniper) at each site. This was to
determine what type of impacts were presently occurring, and they do
not imply that these land use practices are what led to the loss of
pygmy rabbits at any of the extirpated sites (Larrucea and Brussard
2008b, p. 1638). Larrucea and Brussard (2008b, p. 1639) found
agricultural fields at 6 of the 105 historical sites. Most historical
sites occurred in the foothills and not on valley floors where
vegetation was more meadow-like. This may have changed after 1880 as
excessive grazing reduced grasses, increased erosion, and lowered water
tables and fire suppression allowed sagebrush to increase on valley
floors (Miller and Rose 1999, cited in Larrucea and Brussard 2008b, p.
1640), creating pygmy rabbit habitat at these lower elevations.
Summary of Agricultural Impacts
Information indicating loss of sagebrush due to agricultural
conversion in specific portions of the pygmy rabbit's range has been
documented. However, because of the pygmy rabbit's patchy habitat
distribution across the landscape, as discussed earlier, the scope of
loss or modification of sagebrush habitat in general due to
agricultural conversion does not equally relate to the loss or
modification of pygmy rabbit habitat. Based on information in site-
specific areas, agricultural conversion has resulted in some loss of
sagebrush habitat used by pygmy rabbits and likely has resulted in some
localized population declines in areas of Idaho, Montana, California,
Nevada, and Utah.
As presented above, the examples of conversion of sagebrush habitat
are few in number across the range and do not indicate a systematic or
widespread loss of habitat that may have been or is now suitable for
pygmy rabbits. While there has been some documented loss of historical
pygmy rabbit sites due to agricultural conversion, the best available
scientific information does not indicate a significant loss or
modification of habitat, and measureable population decreases
attributed to habitat loss or modification due to agriculture impacts
are not occurring across the range. While sagebrush habitat will
continue to be converted to agricultural lands in the future, it will
occur at a much lower rate as much of the appropriate habitat has
already been converted. Therefore, based on the best available
scientific information, we conclude that sagebrush loss or modification
due to agriculture is not a significant threat to the pygmy rabbit now
or in the foreseeable future.
Sagebrush Treatment
Treatment of sagebrush by mechanical (mowing, rotobeating, roller
chopping, grubbing, chaining, bulldozing, cabling, raking, railing, and
plowing) and chemical methods (herbicide) primarily for rangeland
improvement and grazing management to increase forage production for
domestic and wild ungulates has been common in sagebrush ecosystems
(Connelly et al. 2004, pp. 7-46 to 7-47). Over 5 million ac (2 million
ha) of sagebrush habitat was mechanically or chemically treated or
burned by the 1970s (Crawford et al. 2004, p. 12). According to Braun
(1998, p. 9) mechanical treatments began in the 1930s and continued at
relatively low levels until the late 1990s. While many square miles of
sagebrush habitat have been lost during the last 150 years due to
conversion for agriculture (discussed above), today this conversion
occurs at relatively low levels (70 FR 2255).
Possible effects to pygmy rabbits of mechanical or chemical
sagebrush treatments include injury or death at the time of treatment,
reduction in forage and shelter, temporary or permanent home range
abandonment, increased habitat fragmentation, increased dispersal
barriers, increased predation, and population declines. As a sagebrush
dependent species, complete loss of sagebrush in a large area could
have long-term impacts to pygmy rabbits. Olterman and Verts (1972, p.
25) and Wilde (1978, p. 120) cautioned that the practice of sagebrush
removal from some livestock ranges in Oregon and Idaho, respectively,
could be a threat to the pygmy rabbit in the future. The researchers
noted that land changes should be monitored and adequate ``safeguards''
implemented to reduce excessive clearing of large areas.
Roberts (1998, p. 11) calculated that of the 583,600 ac (236,180
ha) he inventoried for pygmy rabbit occupancy in Lemhi and Custer
Counties, Idaho, 49,000 ac (19,830 ha) (8 percent) were lost due to
sagebrush eradication; Roberts (1998, p. 11) did not estimate the
amount of lost pygmy rabbit habitat. In Oregon, BLM (2007b, pp. 5-6)
documented active pygmy rabbit use at one of eight sites that had
sagebrush strips removed by mowing. It appeared that pygmy rabbits had
been there prior to the mowing (as evidenced by burrows), with
residency continuing following mowing. Mowing may have opened the area
for new growth of herbaceous vegetation which can be beneficial to
pygmy rabbits (BLM 2007b, p. 7).
In Montana, Rauscher (1997, pp. 13-14) reported that sagebrush
removal was a ``popular'' rangeland improvement practice in the
southwestern portion of the State. Sagebrush in the Coyote Creek area
of the Big Sheep Creek Basin has been extensively treated, and only one
active burrow was located. In nearby areas where sagebrush had not been
treated, pygmy rabbits were more abundant. In lower Badger Gulch, BLM
lands border private lands, and pygmy rabbits were found on the public
lands but absent on the private lands where sagebrush had been removed.
However, it is unclear how much sagebrush removal had occurred on the
private lands and whether pygmy rabbits had previously occupied these
same lands.
In Wyoming, Katzner (1994, p. 106) mentioned that sagebrush
eradication may have significant adverse effects on the pygmy rabbit
where they were known to occur in southwestern Wyoming at that time. He
recommended that if sagebrush management is ``mandated,'' management
plans should consider the pygmy rabbit and retain large patches of
sagebrush or corridors connecting areas of suitable habitat.
Welch (2005, p. 10) visited 13 historical pygmy rabbit sites in
Utah and Idaho. He indicated one site was no longer occupied by pygmy
rabbits and had been impacted by range improvement.
In Utah, Holt (1975, p. 159) mentioned a concern that removing
large areas of sagebrush by chaining and spraying in order to plant
grass would harm rabbits, including the pygmy rabbit. Flinders et al.
(2005, p. 7) surveyed habitat in Grass Valley in Piute, Sevier, and
Wayne Counties located in south central Utah. Pygmy rabbit surveys were
conducted in areas slated for sagebrush treatment, but
[[Page 60536]]
where pygmy rabbit surveys had not been previously conducted. Areas
where pretreatment pygmy rabbit surveys (Oak Springs and Praetor
Slopes) had been completed by BLM employees (Flinders et al. 2005, p.
13) were revisited, as well. According to Flinders et al. (2005, p.
13), BLM surveys identified 118 active burrow systems and 85 inactive
ones. Flinders et al. (2005, p. 13) found 14 locations with active
burrow systems and determined all other burrows in treatment areas to
be inactive. BLM surveyed sites recorded as active were found to be
``abandoned'' or plowed when revisited (Flinders et al. 2005, p. 13).
Where pygmy rabbits were still occupying treatment areas, they were
in wide sections of sagebrush that was intact and connected to adjacent
remaining sagebrush (Flinders et al. 2005, p. 13). In undisturbed
sagebrush, pygmy rabbits were in isolated patches (Flinders et al.
2005, p. 13). Flinders et al. (2005, p. 36) thought treatment projects
could be beneficial to pygmy rabbits if the sagebrush stands were left
in wide, connected corridors as this would provide forage as well as
cover. BLM treatment areas revisited found active burrows only where
the sagebrush treatment occurred in mosaics that were connected to
other sagebrush stands or the areas of removal were much smaller and
distances between the treatments were minimal. Patchy, smaller
sagebrush removal more likely mimics the natural historical fire
regime. Flinders (2007, p. 3) reported on his preliminary results from
a multi-year pygmy rabbit study in Grass Valley, Utah and found a
reduction in suitable pygmy rabbit habitat due to sagebrush treatments.
He found pygmy rabbit activity was restricted to a narrow band adjacent
to mature stands of sagebrush and showed significantly decreased
activity within the treated areas. Burrow abandonment was noted
following treatment, and he suggested a 131.2 ft (40 m) buffer between
active burrows and habitat treatment. In Grass Valley, Piute and Sevier
Counties, and Parker Mountain, Wayne County, Utah, Lee (2008, pp. 4, 7)
found lower fecal pellet counts in mechanically-treated sagebrush areas
as compared to untreated sagebrush areas. Average pygmy rabbit fecal
pellet counts decreased with distance from sagebrush (Lee 2008, p. 10).
Lee (2008, p. 11) recommended avoiding treatments of big sagebrush in
areas occupied by pygmy rabbits and in areas with all suitable habitat
conditions. If treatments cannot be avoided, they should leave intact
large swaths of undisturbed mature big sagebrush (Lee 2008, p. 11). Lee
(2008, p. 14) recommended that corridors between residual stands of
sagebrush within a treatment area be maintained for connectivity and
dispersal. Lee (2008, p. 13) recommended that stands of remaining
mature big sagebrush be about 54 yd (490 m) across in any direction,
and the areas of big sagebrush removed should be narrow (44 yd; 40 m).
BLM has proposed a national program to treat vegetation across
several western States to reduce hazardous fuels, control unwanted
vegetation and improve habitat and resource conditions through the use
of prescribed fire, wildland fire, herbicides, manual and mechanical
methods, and biological controls (BLM 2007c, p. 1-3 Abstract, Executive
Summary, Chapters 1 through 7, and Appendices). BLM manages
approximately 261 million ac (105.6 million ha) in 17 western States
including Alaska (BLM 2007c, p. 1-1 Abstract, Executive Summary,
Chapters 1 through 7, and Appendices). States encompassing the range of
the pygmy rabbit are included in this program. BLM estimated that 6
million ac (2,428,166.7 ha) of vegetation would need to be treated
annually over the next 10 years (BLM 2007c, p. 1-7 Abstract, Executive
Summary, Chapters 1 through 7, and Appendices). Estimated acres treated
annually by the various methods include: 2.2 million ac (890,327.8 ha)
by mechanical means; 2.1 million ac (849,858.4 ha) by fire; 932,000 ac
(377,175.2 ha) by herbicides; 454,000 ac (183,731.3 ha) by biological
control; and 271,000 ac (109,672.2 ha) by manual means (BLM 2007c, p.
ES-2 Abstract, Executive Summary, Chapters 1 through 7, and
Appendices). The implementation of this program, methods, acres
treated, and locations are yet to be determined.
Summary of Sagebrush Treatment Impacts
Although loss of sagebrush due to sagebrush treatment for rangeland
and grazing management in specific portions of the pygmy rabbit's range
has been documented, the examples presented above are few in number
across the range and are not indicative of a systematic or widespread
loss of habitat that may have been or is now suitable for pygmy
rabbits. Because of the pygmy rabbit's patchy habitat distribution
across the landscape, the scope of loss or modification of sagebrush
habitat in general due to treatments does not equally relate to loss or
modification of pygmy rabbit habitat. Sagebrush treatment has been
documented to be responsible for loss of sagebrush habitat used by
pygmy rabbits in a few specific areas of Oregon, Idaho, Montana,
Wyoming, Utah and may have resulted in localized population declines.
The known presence of pygmy rabbits prior to treatment is not
documented in all cases and some areas show continued occupancy or use
by pygmy rabbits at some level after treatments were conducted (e.g.
Flinders et al. 2005; Lee 2008).
Depending on the design and size of the sagebrush treatment,
impacts to pygmy rabbits may be minimized, and if designed
appropriately, sagebrush treatments may be beneficial to pygmy rabbits.
We are aware of a BLM proposal to implement sagebrush treatments that
could impact sagebrush habitat in the western United States, however no
actions have been implemented at this time (BLM 2007c). Available
information indicates that a significant loss or modification of
habitat, and measureable population decreases attributed to habitat
loss or modification due to treatment impacts and impacts to the pygmy
rabbit with regard to injury or death, temporary home range abandonment
or permanent shift to adjacent areas, habitat fragmentation, or
increased predation are not occurring across the range. Therefore,
based on the best available scientific and commercial information, we
conclude that sagebrush loss or modification due to treatments is not a
significant threat to the pygmy rabbit now or in the foreseeable
future.
Livestock Grazing
Livestock grazing is the most widespread land use type across
sagebrush communities (Connelly et al. 2004, p. 7-29). Excessive
grazing by domestic livestock during the late 1800s and early 1900s,
along with severe drought, significantly impacted sagebrush ecosystems
and the long-term effects involving plant community and soil changes,
continue today (Yensen 1981, cited in Knick et al. (2003, p. 616). By
the 1940s, animal unit months (AUM) on all Federal lands were estimated
to be 14.6 million, increasing to 16.5 million in the 1950s, however
estimated AUMs decreased to 10.2 million by the 1990s (Miller and
Eddleman 2001, p. 19). Grazing impacts may be associated with the
direct loss of sagebrush vegetation through physical damage by rubbing,
battering, breaking and trampling of seedlings, or habitat degradation
due to associated facilities or actions such as: construction of
fences; wells; water tanks; pipelines which concentrate livestock or
redistribute livestock;
[[Page 60537]]
seeding of crested wheatgrass to increase livestock forage; and weed
infestations.
Impacts of livestock grazing on the arid west include selective
grazing for native species, trampling of plants and soil, damage to
soil crusts, reduction of mycorrhizae fungi, increases in soil
nitrogen, increases in fire frequency, and contribution to nonnative
plant introductions (Belsky and Gelbard (2000, pp. 12-18); Paige and
Ritter (1999, pp. 7-8)). When sagebrush-grass habitats are overgrazed,
native perennial grasses can be eliminated, and shrubs, such as big
sagebrush, tend to form dense monotypic (single species) stands
(Blaisdell 1949, cited in Yensen 1982, p. 25; Tisdale and Hironaka
1981, cited in Paige and Ritter 1999, p. 7). In addition, the
understory becomes sparse with unpalatable perennials (Tisdale and
Hironaka 1981, cited in Paige and Ritter 1999, p. 7) and invasions of
annual species like Bromus tectorum (cheatgrass) can occur (Gabler
1997, p. 96; Rauscher 1997, p. 14). Reduction of native grasses and
increases in invasive plant species may reduce habitat quality and
suitability for pygmy rabbits by reducing summer forage and impeding
their movements or ability to see predators.
Possible effects of livestock grazing include direct injury or
death due to trampling, degradation of sagebrush plant structure
resulting in reduced forage and shelter, habitat fragmentation,
increased predation, reduced grasses and forbs resulting in loss of
summer forage, increased visual capabilities and ease of movement,
trampling of burrows, increased invasive plant species resulting in
reduced visual capabilities and ease of movement, and population
declines. However, livestock grazing in pygmy rabbit habitat has been
noted in the early literature. For example, Dice (1926, p. 27) in
Oregon, found pygmy rabbits near Baker in an area that was overgrazed
by domestic sheep. He stated very little vegetation remained except for
sagebrush and rabbit brush. The patch of habitat being used was about
300 yd long (274.2 m) by 50 yd (45.7 m) wide and was surrounded by low
sagebrush (Dice 1926, p 27).
Flath and Rauscher (1995, p. 2) and Purcell (2006, p. 33) found
that areas of tall, dense sagebrush inhabited by pygmy rabbits were
typically located along streams. Livestock can impact these areas
disproportionately by concentrating in riparian areas where trampling
and vegetation removal can occur (Red Willow Research Inc. 2002, p.
107). These researchers do not indicate any specific pygmy rabbit
locations along streams that have been impacted by livestock grazing.
In Oregon, Hager and Lienkaemper (2007, p. 6) reported that all 157
sites, located mostly on State lands, surveyed for pygmy rabbits had
evidence of cattle grazing. Many areas showed heavy use by cattle which
had resulted in a decrease in shrub cover. Additionally, many of the
areas where no evidence of pygmy rabbit presence was found may have had
potential to support pygmy rabbits, as predicted by a habitat model,
but the habitat may have been rendered unsuitable due to grazing
reducing shrub cover (Hager and Lienkaemper 2007, p. 6). However, it is
unknown whether pygmy rabbits were present previously or were absent
from these areas based on other factors. The BLM (2007b, p. 4) reported
livestock use at one of eight occupied sites surveyed in Oregon.
In Idaho, Red Willow Research Inc. (2000, p. 8) documented pygmy
rabbit sightings on two separate BLM grazing allotments which
demonstrated historical and current grazing activities. Another
sighting occurred on private land subjected to grazing and was also
close to dwellings and agricultural activities (Red Willow Research
Inc. 2000, pp. 8, 11). In Idaho, Roberts (2001, p. 18) concluded that
there was no clear evidence that livestock grazing is detrimental to
pygmy rabbits. In Idaho, White and Bartels (2002, pp. 6, 15) surveyed
11 grazing allotments. Of the 6 allotments where pygmy rabbit sign was
observed, 2 allotments supported active burrows, 2 allotments contained
inactive burrows, and 2 allotments supported burrows of undetermined
status. BLM (2005a, p. 2) found during their surveys, conducted between
2002 and 2005 that pygmy rabbits occurred on their lands containing
portions of grazing allotments. In Idaho, North Wind (2004, p. 12)
mentioned livestock grazing occurred in all areas where pygmy rabbit
sign or sightings occurred. In Idaho, Waterbury (2005, p. 9) mentioned
that an occupied site where a pygmy rabbit was observed (Goldburg site)
in the upper Pahsimeroi Valley was subjected to livestock grazing.
In Montana, Rauscher (1997, pp. 14, 17) found that most pygmy
rabbit sites were grazed to some extent. Pygmy rabbits were found to be
``surviving and even thriving'' at current grazing levels in certain
areas.
In Wyoming, Katzner reported that according to Dorn et al. (1984,
cited in Katzner 1994, p. 5), pygmy rabbits did not occur in his study
area (Historical Quarry Trail region) at Fossil Butte National
Monument, Lincoln County in 1983 at the time when domestic livestock
grazing was terminated in the monument. Katzner and Parker (1997, p.
1071) stated that the apparent dependence of pygmy rabbits on a dense
understory, provided in part by dead shrubs and extensive canopies, may
explain population declines in the pygmy rabbit in grazed sagebrush-
steppe habitat in the western United States. Lands grazed intensively
by domestic herbivores often have relatively low structural complexity
and may not support pygmy rabbit populations adequately. The physical
destruction of dense, structurally-diverse patches of sagebrush, and
the corridors that connect them, result in fragmented, unsuitable big
sagebrush habitat for pygmy rabbits (Katzner and Parker 1997, p. 1071).
For a species that eludes predators in sagebrush habitat, a reduction
in canopy cover would increase the vulnerability of pygmy rabbits to
predation (Bailey 1936, p. 111; Orr 1940, p. 197; Wilde 1978, pp. 115-
116; Katzner 1994, pp. 50, 52-53). Clark and Stromberg (1987, p. 76)
remarked that overgrazing, which has increased the sagebrush-grass
ratio, may decrease pygmy rabbit populations.
In Nevada and California, Larrucea (2006 p. 8) stated that
livestock grazing at inappropriate levels can be detrimental for the
degradation of sagebrush habitat. At reasonable levels it may be
beneficial (Larrucea 2006, p. 8; Larrucea 2007, p. 34). Most of the
pygmy rabbit burrows on the BLM lands in the Surprise FO were in areas
available to grazing (Larrucea 2006, p. 8). In Nevada and California,
Larrucea and Brussard (2008b, p. 1638) found cattle grazing occurred at
83 percent of historical pygmy rabbit sites; 38 percent showed current
pygmy rabbit activity. If sites with additional impacts were eliminated
and only cattle grazing impacts are considered, this increased to 62
percent of sites that supported current pygmy rabbit activity (Larrucea
and Brussard 2008b, p. 1639). Grazing was compatible with pygmy rabbits
if grazing occurs at levels that left sagebrush plants intact and soils
were not overly compacted (Larrucea 2007, p. 58). Larrucea and Brussard
(2008a, p. 697) found increasing amounts of understory stem density was
associated negatively with current pygmy rabbit presence at a site.
Pygmy rabbits, by foraging for forbs and grasses near their burrows,
may create areas of little understory. An understory that is free of
grasses and forbs may be beneficial by reducing movement restrictions
and increasing pygmy rabbit's ability to detect predators (Weiss and
Verts 1984, p. 568). The Southern Nevada Water
[[Page 60538]]
Authority (SNWA) (2008, p. 15) stated that data collected during their
surveys conducted in 2005 and 2006 in Nevada (SNWA 2007, entirety)
found 84 percent of the sites with documented pygmy rabbit occurrence
existed in areas of moderate grazing. SNWA (2008, p. 15) suggested that
given that recent occurrence data overlaps with grazing practices,
there is little evidence to suggest that light to moderate grazing is
significantly detrimental to pygmy rabbit in Nevada.
In Utah, Janson (2002, p. 31) did not attempt to measure grazing
intensity during his earlier studies. While he observed a scarcity of
grasses and forbs in the Cedar City area compared to the Blue Springs
area, efforts to collect and observe pygmy rabbits seemed to be similar
on either site. The difference between the amount of shrubs to
herbaceous vegetation between the two sites, due to grazing or some
other factor, did not seem to affect the populations. He did state that
grazing intensities high enough to break down the sagebrush plants and
reduce their density would be detrimental to pygmy rabbits. Although it
is unclear how many of the four sites he considered overgrazed, Larsen
et al. (2006, p. 5) found historical pygmy rabbit sites in Tooele
County, Utah that showed evidence of overgrazing.
Trampling of burrows by livestock has been reported in Montana by
Rauscher (1997, p. 14) and in Idaho by Red Willow Research Inc. (2002,
p. 54). This could cause the death of young rabbits in natal burrows or
injury or death of adults. Red Willow Research Inc., (2002, pp. 54-55)
reported a burrow system in Idaho that was subjected to cattle trailing
on at least two separate occasions within a period of two months or
less. After the initial event, only two of ten active burrows were
still open. A second visit showed additional trailing activities, and
no open burrows or recent sign were found, indicating ``that domestic
livestock can have an immediate and detrimental effect upon burrow
systems'' (Red Willow Research Inc., 2002, pp. 54). This assumes that
no other influences were involved, and there was no further monitoring
of the area to determine if pygmy rabbits returned to the area at a
later date.
Summary of Livestock Grazing Impacts
Livestock grazing occurs in all seven States where pygmy rabbits
occur. Researchers suggest that livestock grazing, particularly
overgrazing, may negatively impact some sagebrush habitat used by pygmy
rabbits and may result in some localized population declines. The
potential effects of livestock grazing on sagebrush habitat and pygmy
rabbit populations, while widespread across the pygmy rabbit's range
have not been documented to impact pygmy rabbits at the population
level or result in documented measurable population declines as a
result of overgrazing.
As described above, there are several examples where pygmy rabbits
have been document to continue to occupy areas grazed by livestock,
which may indicate an apparent compatibility between livestock grazing
and area use by pygmy rabbits under certain grazing conditions. Other
documentation suggests possible habitat loss or degradation, site
abandonment, habitat fragmentation, increased predation, or injury of
pygmy rabbits due to livestock overgrazing and trampling. However,
based on survey information, there is no indication of a causal
relationship between livestock grazing and pygmy rabbit site
abandonment or avoidance. Studies do not indicate that there is a level
of livestock grazing that influences pygmy rabbit site occupancy. While
the Service is aware of a report of burrow trampling, we are not aware
of any studies relating actual site abandonment, increased predation,
death, or injury due to livestock grazing or trampling. Reduced grasses
and forbs may increase the pygmy rabbits' ability to see and evade
predators. Some survey reports suggest that livestock grazing is
degrading pygmy rabbit habitat in some locations. Our review of the
best available scientific data indicate that measureable population
decreases attributed to habitat modifications from livestock grazing
are not occurring across the range. Therefore, we conclude that
livestock grazing is not a significant threat to the pygmy rabbit now
or in the foreseeable future.
Nonnative Invasive Plants
Paige and Ritter (1999, p. 8) suggest that the greatest change to
sagebrush shrub lands has been the invasion of the nonnative grasses
and forbs, especially cheatgrass. Cheatgrass is a rapid colonizer of
disturbed areas and is persistent in replacing native species (Mack
1981, Yensen 1981, and Whisenant 1990, cited in Paige and Ritter 1999,
p. 8). Cheatgrass alters fire and vegetation patterns in sagebrush
habitats as it creates a continuous fine fuel that easily carries fire
(Paige and Ritter 1999, p. 8). Where it dominates, it can carry fires
over large distances, and it burns more frequently than native
vegetation (Paige and Ritter 1999, p. 8). It also matures and dries
earlier than native vegetation, increasing the likelihood of a fire
earlier in the season (Young and Evans 1978, Whisenant 1990, and Knick
and Rotenberry 1997, cited in Paige and Ritter 1999, p. 8).
The total acreage of invasive plant infestations has been reported
with varying estimates. Pellant and Hall (1994, p. 109) reported on the
1992 distribution of cheatgrass and Taeniatherum asperum (medusa head),
the primary alien grass invaders of disturbed and fire-altered
rangelands in the Intermountain area of the western United States.
Approximately 3.3 million ac (1.3 million ha) of rangeland administered
by the BLM in Nevada, Oregon, Utah, Washington, and Idaho are dominated
by these two species (Pellant and Hall 1994, p. 109). Another 76.1
million ac (30.8 million ha) of public rangeland was classified as
infested or susceptible to infestation by these two species (Pellant
and Hall 1994, p. 109). It has been estimated that 3 million ac (1.2
million ha) of public lands in the Great Basin have been converted to a
cheatgrass monoculture with another 14 million ac (5.7 million ha)
assumed to be infested, and it is likely that conversion is inevitable
(Knapp 1996, West 1999, cited in Larrucea 2007, p. 61). Though
estimates of total area supporting cheatgrass vary widely, cheatgrass
is a significant presence in western rangelands (75 FR 13935).
BLM (1996, p. 6) estimated invasive plant species covered at least
8 million ac (3.2 million ha) of BLM lands as of 1994 and predicted 19
million ac (7.7 million ha) would be infested by 2000. A qualitative
BLM survey in 1991 covering 98.8 million ac (40 million ha) of BLM-
managed land in Washington, Oregon, Idaho, Nevada, and Utah reported
introduced annual grasses were a dominant or significant presence on
17.2 million ac (7 million ha) of sagebrush ecosystems (Connelly et al.
2004, pp. 5-10). In reference to the same BLM survey, Zouhar (2003, p.
3 cited in 75 FR 13935) estimated an additional 62 million ac (25
million ha) had less than 10 percent cheatgrass understory, but were
considered to be a risk of cheatgrass invasion. BLM has reported that
as of 2000, invasive plants occupied about 29 million ac (11.7 million
ha) of BLM lands in the Washington, Oregon, Idaho, Utah, Nevada (BLM
2007a, pp. 3-28 as cited in 75 FR 13935).
Connelly et al. (2004, p. 7-15) estimated the risk of cheatgrass
invasion into sagebrush and other natural vegetation in a portion of
the southern and northern Great Basin. They projected, based on
elevation, landform, and south-facing slope parameters, that 80 percent
of the land area in the Great Basin is susceptible to displacement by
[[Page 60539]]
cheatgrass and of that area, greater than 65 percent is estimated to be
at moderate or high risk within 30 years (Connelly et al. 2004, pp. 7-
16 to 7-17). Wyoming-basin big sagebrush and salt desert scrub, which
occupy over 40 percent of the Great Basin, are the vegetation types
most susceptible to cheatgrass displacement (Connelly et al. 2004, p.
7-17).
Restoration or rehabilitation of areas to sagebrush after invasive
plant species, especially annual grasses, become established is
difficult. Only about 3 to 34 percent of recent vegetation treatments
performed by BLM in areas of annual grassland monocultures were
successful (Carlson 2008b, pers. comm., cited in 75 FR 13937). The
success of treatments often depends on factors such as precipitation
received at the treatment site (Pyke, in press, p. 30).
Nonnative invasive plant species may impact pygmy rabbits
throughout their range by replacing native grasses and shrubs used by
pygmy rabbits, hindering their ability to see or move, and increasing
detection by predators. In Oregon, only 2 of 51 sites occupied by pygmy
rabbits in 1982 contained appreciable amounts of cheatgrass (Weiss and
Verts 1984, p. 568). This led the authors to suspect that pygmy rabbits
avoid areas containing annual grasses because it can restrict their
movements or ability to see, especially when they are attempting to
escape predators. However, it is unclear whether annual grasses are
playing a role in pygmy rabbits not occupying a site. The authors did
not indicate whether or not unoccupied sites surveyed had cheatgrass.
In Idaho, invasive plants were reported at all nine study areas
investigated by Red Willow Research Inc. (2002, pp. 38, 45, 59, 65, 72,
80, 87, 92, 97). Gabler (1997, p. 94) predicted 10 study sites would be
used by pygmy rabbits, but later found large patches of cheatgrass on 8
of those sites, and that the pygmy rabbit did not use these sites.
Other factors, such as large amounts of dead sagebrush, and/or sparse,
short sagebrush, and thick grass cover, may have contributed to pygmy
rabbit absence in those sites (Gabler (1997, p. 94). BLM (2005a, p. 2)
indicated that no evidence of pygmy rabbits was found at any of the
sites (no number provided) in Idaho surveyed in 2005 where cheatgrass
was a major component of the understory. Burak (2006, p. 68) found that
cheatgrass made up little of the grass community within his entire
study area; areas occupied by pygmy rabbit had approximately 1 percent
cheatgrass cover and unoccupied areas had less than 1 percent.
In Nevada and California, Larrucea and Brussard (2008b, p. 1641)
stated that wide expanses of cheatgrass monocultures may provide a
barrier to pygmy rabbit dispersal as they rely on shrub cover for
protection from predators. Larrucea and Brussard (2008a, p. 697) found
cheatgrass presence was negatively associated with pygmy rabbit
presence at a site. Once established it may be difficult for pygmy
rabbits to burrow into the dense root mats (Larrucea and Brussard
2008a, p. 697). SNWA overlaid a Nevada Natural Heritage Program
invasive annual grass index map (most of which was cheatgrass) (NHP
2006, cited in SNWA 2008, p. 14) with 2000 to 2007 pygmy rabbit
occurrence data from various sources. The overlay indicates a large
portion of pygmy rabbit occurrences are within areas of relatively low
cheatgrass cover. This map serves as a relative density index of
cheatgrass rather than actual current ground cover because of the
remote sensing and statistical models from which it is derived. While
the underlying models tend to underestimate index values for sites with
high invasive annual grass densities, the general pattern of low to
high densities is well represented on the map. The map is quite
accurate for sites where invasive annual grass cover is low or
nonexistent. SNWA concluded that cheatgrass has not had a major impact
on pygmy rabbit occurrence or geographic range in east-central Nevada
(SNWA 2008, p. 14).
Larsen et al. (2006, p. 5) visited four historical pygmy rabbit
sites in Tooele County, Utah that were unoccupied by pygmy rabbits.
They mentioned these sites showed evidence of cheatgrass invasion, but
it is unclear if all four sites supported cheatgrass.
Summary of Nonnative Invasive Plant Impacts
Based on information for a few specific areas, presence of invasive
plant species has been documented and may have some impact on pygmy
rabbit presence or their movements in Oregon, Idaho, Nevada,
California, and Utah. These examples, as discussed above, are few in
number and are not considered to be indicative of a widespread habitat
condition. It is unclear whether the presence of cheatgrass or other
invasive plant species caused pygmy rabbits to not occupy an area or if
other factors may have also played a role. The scope of loss or
modification of sagebrush habitat in general due to nonnative plant
invasion does not equally relate to the loss or modification of pygmy
rabbit habitat because pygmy rabbit's habitat is patchily distributed
across the landscape.
Varying estimates have been made regarding the amount of area
invaded by invasive plant species in the western United States, and
some predictions indicate it could take decades for cheatgrass to
invade sagebrush and other natural vegetation in a portion of the Great
Basin. The Service recognizes that invasion of sagebrush habitat by
nonnative plant species is a concern based on their ability to
outcompete sagebrush, the difficulty in controlling them once
established, and their interaction with other threats, such as fire.
However, there is no indication of a significant loss or modification
of habitat, and measureable population decreases attributed to habitat
loss or modification due to nonnative plant species, especially
cheatgrass, and pygmy rabbit site abandonment or avoidance are not
occurring across the range. Available information does not provide a
causal relationship between a reduction in pygmy rabbit visual
capabilities and ease of movement due to nonnative plant species.
Therefore, based on the best available scientific and commercial
information, we conclude that nonnative invasive plant species in pygmy
rabbit habitat is not a significant threat to the pygmy rabbit now or
in the foreseeable future.
Fire
The effect of fire on sagebrush habitats depend on the sagebrush
species present, the composition of understory species, and the size,
frequency, and intensity of the fire. Estimates of mean fire intervals
indicated in the literature vary widely: 12 to 15 years for mountain
big sagebrush (Miller and Rose 1999, p. 556), 13 to 25 years (Frost
1998, cited in Connelly et al. 2004, p. 7-4), greater than 50 years for
big sagebrush communities (Whisenant 1990, cited in McArthur 1994, p.
347), 20 to 100 years (Peters and Bunting 1994, p. 33), 35 to 100 years
(USFS 2000, p. 7), and 10 to 110 years depending on sagebrush species
and geographic area (Kilpatrick 2000, p. 1).
Natural fires in sagebrush stands characteristically result in
incomplete burns leaving areas of unburned sagebrush (Huff and Smith
2000, cited in 70 FR 2264). These unburned areas appear to be important
in the future recolonization of the sagebrush community by providing
sources of sagebrush seed (Huff and Smith 2000, cited in 70 FR 2264).
Prior to European immigrant settlement, fire patterns in sagebrush
communities were patchy,
[[Page 60540]]
particularly in Wyoming big sagebrush, due to the limited and
discontinuous fuels and unburned areas that remained after a fire
(Miller and Eddleman 2001, p. 17).
In parts of the Great Basin, a decline in fire occurrence since the
late 1800's has been reported in several studies coinciding with fire
suppression and reduction of fuels by introduced livestock (Miller and
Rose 1999, pp. 556-557; Kilpatrick 2000, p. 6; Connelly et al. 2004, p.
7-5). Long fire intervals and fire suppression can result in increased
dominance of conifer species, such as western juniper (Juniperus
occidentalis) (Wrobleski and Kauffman 2003, p. 82) resulting in almost
complete loss of shrubs in localized areas (Miller and Eddleman 2001,
p. 20).
Burning can also damage perennial grasses, allowing cheatgrass to
increase (Stewart and Hull 1949; Wright and Britton 1976, cited in
Yensen 1982, p. 28). The presence of cheatgrass extends the fire season
and carries a fire into areas where burning would not normally occur or
can make fires difficult to control (Yensen 1982, pp. 28-29; Billings
1994, p. 24). The invasion of nonnative annuals, such as cheatgrass and
medusa head has resulted in increases in the frequency and number of
fires within sagebrush habitats (USFS 2000, p. 153; Connelly et al.
2004, pp. 5-9 to 5-10). Sagebrush does not quickly re-establish after
fires, while nonnative grasses can recover quickly and increase,
effectively preventing sagebrush return. Due to this relationship
between fire and the spread of invasive plants, large areas of
sagebrush in the western United States have been converted to
cheatgrass (Connelly et al. 2004, p. 7-14).
Generally, fire tends to extensively reduce the sagebrush component
within the burned areas. The most widespread species of sagebrush, big
sagebrush (A. tridentata spp.) (McArthur 1994, p. 347), is killed by
fire. It does not re-sprout after burning (Agee 1994, p. 14; Braun
1998, p. 9) and can take over 30 years to recolonize an area (Wambolt
et al. 2001, pp. 244, 247). Depending on the species, sagebrush can
reestablish itself within 5 years of a burn, but it may take 15 to 30
years to return to pre-burn densities (Bunting 1984; and Britton and
Clark 1984, cited in Paige and Ritter 1999, p. 6). Billings (1994, p.
26) documented slow shrub succession following a burn in western
Nevada, with little sagebrush recovery after 45 years. This suggests
that these sagebrush subspecies evolved in an environment where
wildfire was infrequent (30 to 50 year intervals) and patchy in
distribution (Braun 1998, p. 9).
Connelly et al. (2004, p. 7-6) summarized fire statistics from
records of wild and prescribed fires in the sagebrush biome and found
the total area burned and the number of fires increased from 1960 to
2003. In the 100 million ac (40.5 million ha) sagebrush-steppe
ecoregion or drier sagebrush areas, fire regimes have become more
frequent (USFS 2000, p. 195). Miller et al. (2008, p. 39) also mapped
fires from 1960 through 2007 and found that the number of fires and
total area burned across the Greater Sage-grouse Conservation Area
increased in each of the geographic subdivisions except the Snake River
Plain from 1980 through 2007. Average fire size increased only in the
Southern Great Basin during this period. Location of fires since 1960
was related to cheatgrass distribution particularly within the Snake
River Plain and Northern Great Basin (Miller et al. 2008, p. 39).
Wildfires have removed large areas of sagebrush in recent years.
Although fire occurs throughout the sagebrush ecosystem, fire has
disproportionately affected Idaho, Nevada, Oregon, and Utah (Baker, in
press, p. 20). In these states combined, about 27 percent of the
sagebrush habitat has burned since 1980 (Baker, in press, p. 43). Total
area burned each year on or adjacent to BLM- administered lands was
variable from 1997 through 2006 (Miller et al. 2008, pp. 39-40); most
total area burned was in cheatgrass regions in Oregon, Idaho, and
Nevada (Miller et al. 2008, p. 40). A number of fires have occurred in
Idaho that have exceeded 100,000 ac (40,469 ha) (Roberts 2003a, p. 14).
The largest contiguous patch of sagebrush habitat in southern Idaho
covered about 700,000 ac (283,000 ha) (Michael Pellant, BLM, quoted in
Healy 2001, p. 3), and during 1999 to 2001 about 500,000 ac (202,000
ha) of this area burned. In Nevada, 1,277 fires in 2001 impacted
654,253 ac (264,773 ha) on public and private lands (BLM 2001, p. 3).
In 2002, BLM reported 771 fires that impacted 77,551 ac (31,384 ha) on
public and private lands in Nevada (BLM 2002, p. 3). In 2006, over
988,400 ac (400,000 ha) of sagebrush steppe and potential pygmy rabbit
habitat was burned in Elko County (Larrucea and Brussard 2008b, p.
1641). Over 9 fire seasons in Nevada (1999-2007), about 2.5 million ac
(1.0 million ha) of sagebrush habitat were burned. This represents
about 12 percent of the extant sagebrush in Nevada (Espinosa and Phenix
2008, p. 3). Most of these fires occurred in northeast Nevada (75 FR
13933). The amount of occupied pygmy rabbit habitat impacted by these
fires is unknown.
Sagebrush restoration efforts following fire are complicated by
invasive, nonnative, annual plant species, costs, equipment
limitations, availability of suitable seeds, limited knowledge of
appropriate methods, and abiotic factors (Hemstrom et al., 2002, pp.
1250-1251, Pyke, in press, p. 29). Habitat rehabilitation following
fire has increased in recent years from 69,436 ac (28,100 ha) in 1997
to 3.9 million ac (1.6 million ha) in 2002 with treatments primarily
occurring in Oregon, Idaho, and Nevada (Connelly et al. 2004, p. 7-35).
While not all burned habitat is rehabilitated, fires which occur on
public lands will likely experience some level of post-fire restoration
(75 FR 13934).
Fire, either wild or prescribed, has been documented within the
range of the pygmy rabbit and could result in long-term habitat loss or
modification of pygmy rabbit habitat across its range. Possible impacts
to pygmy rabbits include injury or death, reduction in forage and
shelter, increased habitat fragmentation, increased predation, barriers
to movement, or home range abandonment. Although information is
available relating fire and its impact to pygmy rabbits, several
studies have shown pygmy rabbit presence after fires.
In Idaho, researchers have noted burn areas on the lands they have
surveyed for pygmy rabbits. For example, Roberts (1998, p. 11) stated
that of the 583,600 ac (236,175 ha) he inventoried, about 2,500 ac
(1,012 ha) had been temporarily removed due to fire (a loss of 0.4
percent). White and Bartels (2002, pp. 8-9) indicated of the 133,067 ac
(53, 851 ha) they surveyed, 23,660 ac (9,575 ha) had been affected by
wildfire within the last 15 years and that historical pygmy rabbit
locations had been impacted. The sagebrush had been burned and habitat
for the pygmy rabbit was not available. In these studies, researchers
did not indicate how much of this acreage might have been occupied by
pygmy rabbits and the number of historical sites where habitat may have
been removed is unknown. However, Welch (2005, p. 10) visited
historical pygmy rabbit sites in Utah and Idaho and documented some
sites (2 of 13) were, or were likely impacted by fire.
Other researchers have reported impacts of fire on local pygmy
rabbit populations. For example, Gates and Eng (1984, cited in Tesky
1994, p. 8) reported the deaths of ``several'' pygmy rabbits in an area
where the fire advanced rapidly within a prescribed burn in Idaho. They
thought pygmy
[[Page 60541]]
rabbits may be capable of escaping slow-moving fires but could be
burned or die of asphyxiation in others (Gates and Eng 1984, cited in
Tesky 1994, p. 8). Gates and Eng (1984, cited in Tesky 1994, p. 9) also
reported that 2 months following a fire in big sagebrush-grassland
community, only 3 of 11 radio-collared pygmy rabbits were alive. Of the
eight lost, seven were due to predation. They speculated that the loss
of big sagebrush from their home ranges probably increased
vulnerability to predation. Some of the surviving pygmy rabbits
(presumably other uncollared pygmy rabbits) abandoned their home ranges
and moved to new home ranges in adjacent unburned sites (Gates and Eng
1984, cited in Tesky 1994, p. 9). Roberts (2001, p. 17) mentioned a
1966 burn near Gilmore Summit, Idaho, that had not regenerated to
suitable habitat, and pygmy rabbits had not recolonized the area.
Rachlow and Witham (2006, p. 6) suggested that large fires that removed
sagebrush in the Camas Prairie of south central Idaho near the
locations of known populations may reduce or eliminate successful
movement of pygmy rabbits among some populations.
In Nevada, the Service (1995, p. 2) reported that a survey
conducted after a prescribed fire on the Sheldon National Wildlife
Refuge in an area previously inhabited by pygmy rabbits found no
evidence of their use afterwards. Larrucea (2006, p. 5) found no active
pygmy rabbit sites in areas burned between 1981 and 2002 within the
Surprise FO boundary; however, few fires occurred, and they were small
in size (Figure 5 in Larrucea 2006, p. 14). Larrucea and Brussard
(2008b, p. 1641) found 16 percent of the 105 historical pygmy rabbit
sites in Nevada and California had been impacted by fire. Larrucea
(2007, p. 61) found fire to be the strongest predictor of loss of pygmy
rabbits from a site in Nevada and California; the greater the fire's
intensity, the fewer the patches of intact sagebrush will remain. Pygmy
rabbits were found on the edges of large burned areas (Midas-Tuscarora
Road, NV), but the burned areas had not reverted to suitable pygmy
rabbit habitat (Larrucea 2007, pp. 61-62).
In contrast to the above studies, other researchers have mentioned
burned areas that showed use by pygmy rabbits. In Idaho, a pygmy rabbit
sighting reported by Red Willow Research Inc. (2000, p. 8) on BLM lands
that had been impacted by wildfire in 1999 showed active use of the
site. White and Bartels (2002, p. 13) mentioned that wildfires in the
1990's severely affected the pygmy rabbit population, though some
individuals remained. At one of her study sites, Waterbury (2005, p.
11) found occupied burrows in an area where prescribed burns had
occurred during 1993 to 1995. Waterbury (2006, p. 13) discovered a
pygmy rabbit population in an old burn area in upper Spar Canyon.
In Montana, Rauscher (1997, p. 14) reported that a prescribed burn
in 1980 near Badger Pass, Montana, had been recolonized by pygmy
rabbits. He did not know how long this process had taken or if pygmy
rabbit densities had reached preburn levels. Bockting (2007 p. 1) found
prescribed burns of about 500 ac (202 ha) have been implemented in
pygmy rabbit habitat to reduce Pseudotsuga menziesii (Douglas fir)
encroachment. Fire patterns minimized burning in the dense sagebrush. A
mosaic burn pattern was allowed. Mechanical treatments (chainsaws) have
also been used to remove Douglas fir. Within one unit, pygmy rabbit
burrows were identified prior to the burn and revisited after the burn.
Where the sagebrush habitat was not burned over, the burrows were still
occupied (Bockting (2007 p. 1). It appears that small burns that create
a mosaic do not significantly impact pygmy rabbits as long as
surrounding habitat is maintained and the entire population is not
lost.
In Nevada, SNWA (2008, pp. 14-15) overlaid BLM's 1980 to 1996 and
1997 to 2007 wildlife data (BLM 2007b, cited in SNWA 2008, p. 14) with
Nevada's 2000 to 2007 pygmy rabbit occurrence data from various
sources. They stated that review of their map indicates that a large
portion of Nevada pygmy rabbit occurrence data falls in areas with
relatively low numbers and sizes of wildfires, especially in east-
central Nevada. Large numbers and sizes of wildfires have not occurred
throughout most of the historical and current pygmy rabbit range in
east-central Nevada. They concluded that wildfires have not caused
major declines in pygmy rabbits or their habitat, or pygmy rabbit
occurrence or geographic range in east-central Nevada.
Summary of Fire Impacts
Fire has impacted sagebrush ecosystems in the past and will
continue to do so in the future, likely in increasing frequency and
size of burned area. This increase in frequency is likely to be
attributed to increases in invasive plant species cover, especially
cheatgrass, as discussed above, as well as possible impacts of climate
change as discussed below. Some studies summarized above have shown
pygmy rabbits to have been negatively affected in some specific areas
within their range. However, other studies have shown pygmy rabbits are
not affected or are able to recolonize burned areas. Based on reports
from site-specific areas in Idaho, Montana, California, Nevada, and
Utah, fire has resulted in some loss of sagebrush habitat used by pygmy
rabbits and has likely resulted in some population declines. Of the
available examples showing loss of habitat, these are few in number
across the range and are not indicative of systematic or widespread
loss of habitat that may have been or is now suitable for pygmy
rabbits. The scope of loss or modification of sagebrush habitat in
general due to fire does not equally relate to loss or modification of
pygmy rabbit habitat because the pygmy rabbit habitat occurs in a
patchy distribution across the landscape. Some fires have resulted in
loss of individuals, forage, and shelter for pygmy rabbits which may
have led to an increased vulnerability to predation (Gates and Eng
1984, cited in Tesky 1994, pp. 8-9). Abandonment of home ranges has
been indicated at some specific sites but with the surviving
individuals moving to adjacent unburned areas (Gates and Eng 1984 cited
in Tesky 1994, p. 9).
Recolonization or use of burned areas has occurred in other site-
specific areas. It also appears that the adverse impacts of fire may be
minimized if burns are small, reducing possible habitat fragmentation
and barriers to movement; if they occur in a mosaic pattern; if
surrounding habitat is maintained to provide habitat; and if all
members of a population are not lost. Additionally, studies in Montana
and Idaho have indicated previously burned areas used or recolonized by
pygmy rabbits (Rauscher 1997, Red Willow Research Inc. 2000, White and
Bartels 2002, Waterbury 2005, 2006). Also in Montana a study indicated
that a small mosaic fire, leaving some surrounding habitat, remained
occupied by pygmy rabbits (Bockting 2007). Fire effects on sagebrush
habitats depend on the sagebrush species, the composition and density
of understory species, as well as the size, frequency, speed, burn
pattern, and intensity of the fire. While it is not possible to predict
the location or extent of future fires within pygmy rabbit habitat, the
numbers of fires are likely to increase in the future; however, pygmy
rabbits have shown an ability to survive and recolonize areas after
some fire events. Based on our review of the best available scientific
information, we conclude habitat loss or modification as a result of
fire is not a significant threat to the pygmy rabbit now or in the
foreseeable future.
[[Page 60542]]
Pinyon-Juniper Woodlands Encroachment
Pinyon-juniper woodlands have increased in the Intermountain West
an estimated 10 fold since European immigrant settlement (Miller and
Tausch 2001, p. 15) resulting in the loss of many sagebrush-bunchgrass
communities. The major factor cited for this increase is the decrease
in fire return intervals (Miller and Tausch 2001, p. 25). Other factors
attributed to this expansion include historical livestock grazing
patterns, which reduced fine fuel buildup that more readily carried
fire, and possibly climate change (Miller and Rose 1999, p. 551; Miller
and Tausch 2001, p. 15).
Connelly et al. (2004, pp. 7-8 to 7-12) estimated the risk of
pinyon-juniper displacement of sagebrush within 30 years for a large
portion of the Great Basin based on site elevation, proximity to extant
pinyon-juniper, precipitation, and topography. They projected that 60
percent of the sagebrush in the Great Basin was at low risk of being
displaced by pinyon-juniper, 6 percent was at moderate risk, and 35
percent was at high risk (Connelly et al. 2004, p. 7-12). It appeared
that mountain big sagebrush was the type most at risk for pinyon-
juniper displacement (Connelly et al. 2004, p. 7-13). They cautioned
that additional field research is necessary to support their
projections (Connelly et al. 2004, pp. 7-14).
Surveys (BLM 2006a, pp. 4-5) conducted in Oregon found junipers at
6 of 7 sites surveyed, and pygmy rabbits occupied 5 of these sites with
an additional site being inconclusive in terms of occupancy. In areas
where pygmy rabbit burrows were found close to junipers, tree density
ranged from 5 to 15 mature (70 to 120 years old) trees per ac (2 to 6
per ha), and trees more than 20 years old were common. The areas still
had a sagebrush and grass understory. Burrows were within 50 yd (45.7
m) of junipers. . BLM (2007b, pp. 7-8) mentioned juniper control may
benefit the pygmy rabbit populations at two of the eight occupied sites
surveyed in Oregon. Juniper control may benefit pygmy rabbit
populations at these sites before canopy closure affects the understory
(BLM 2006a, p. 4; 2007b, p. 7).
Welch (2005, p. 10) indicated 1 of 13 historical pygmy rabbit sites
visited in Utah and Idaho were impacted by juniper encroachment. Larsen
et al. (2006, p. 5) found historical pygmy rabbit sites in Tooele
County, Utah, showed evidence of pinyon-juniper encroachment, but he
did not indicate if all four sites had been encroached by pinyon-
juniper or whether there was remaining suitable pygmy rabbit habitat.
Pinyon-juniper encroachment may have a negative impact on pygmy
rabbits. In Nevada, pinyon-juniper woodland populations have increased
almost 250 percent in distribution during the last 150 years (Tausch et
al. 1981, cited in Larrucea and Brussard 2008b, p. 1640). These
conifers slowly replace the sagebrush and convert it to woodland
habitat, eliminating the understory (Miller et al. 2000, cited in
Larrucea and Brussard 2008b, p. 1640).
Larrucea and Brussard (2008b, p. 1640) found that a few of these
trees at a site generally meant that pygmy rabbits were not present.
Larrucea and Brussard (2008b, p. 1639), surveying sites in California
and Nevada, showed that 14 percent of historical pygmy rabbit sites
showed signs of pinyon-juniper woodland conversion. Of these sites,
only one had current pygmy rabbit activity (Larrucea and Brussard
2008b, p. 1639). At 6 of the 14 extirpated pinyon-juniper sites, pygmy
rabbits were known to occur lower in the valley where sagebrush habitat
existed (Larrucea and Brussard 2008b, p. 1640). However, based on the
information available a significant loss or modification of habitat and
measureable population decreases from site abandonment or avoidance
attributed to pinyon-juniper encroachment are not occurring across the
range.
Summary of Pinyon-Juniper Woodlands Encroachment Impacts
Based on our review of the best available information, we found few
studies which document negative effects of pinyon-juniper expansion on
pygmy rabbit populations. Based on the studies cited above, pinyon-
juniper expansion has occurred in some occupied pygmy rabbit habitat in
Oregon, Idaho, California, Nevada, and Utah; however, pygmy rabbits
continued to be present at a number of these sites. Larrucea and
Brussard (2008b, p. 1639), surveyed sites in California and Nevada and
found only 14 percent of historical sites showed signs of pinyon-
juniper woodland conversion, and one had current activity. BLM (2006a,
p. 4) conducted surveys in Oregon and found junipers at 6 of 7 sites,
and pygmy rabbits continued to occupy a majority of these sites. Welch
(2005, p. 10) found only 1 of 13 historical sites in Utah and Idaho
showed signs of juniper encroachment. Larsen et al. (2006, p. 5) found
four historical sites in Utah may have showed pinyon-juniper
encroachment. The encroachment of pinyon-juniper into occupied pygmy
rabbit habitat is a slow process, and pygmy rabbits may be able to
inhabit those areas or shift their home range to adjacent areas if
pinyon-junipers habitat becomes established at a site. Therefore, based
on the best available scientific and commercial information, we
conclude that pinyon-juniper expansion is not a significant threat to
the pygmy rabbit now or in the foreseeable future.
Urban and Rural Development
Historical destruction of sagebrush habitat for urban development
has occurred (Braun 1998, pp. 6-7) with more recent expansion into
rural areas causing additional loss (Braun 1998, pp. 6-7). Since 1950,
the western United States has experienced rapid human population growth
with regional rates higher than the national average (Brown et al. 2005
cited in Leu and Hanser in press, p. 4). Fifty percent of all
population growth in the United States from 1990 to 2000 occurred in
western states (Perry and Mackun 2001 cited in Anderson and Woosley
2005, p. 6). The amount of uninhabited area in the Great Basin (Idaho,
California, Nevada, and Utah) has decreased from 90,000 km\2\ (34,749
mi\2\) in 1990 to less than 12,000 km\2\ (4.633 mi\2\) in 2004 (Knick
et al. in press, p. 20). The petitioner contended that power lines,
fences, and roads that are associated with urban and rural development
may have also resulted in the direct loss of sagebrush habitat and
subsequently affected pygmy rabbits.
Urban and rural development has impacted and may impact pygmy
rabbit populations on a local scale. Possible effects to pygmy rabbits
include loss of food and shelter, home range abandonment, injury or
death at the time of vegetation clearing, habitat fragmentation, and
population declines. Power poles and fences can provide hunting and
roosting perches and nesting support, for many raptor species that are
known to prey upon pygmy rabbits. In addition to direct habitat loss,
roads may disrupt pygmy rabbit dispersal movements, and exacerbate
potential impacts due to habitat fragmentation.
Some research indicates that pygmy rabbits can occur where humans
are present, while other research indicates that the human-developed
habitat is not inhabited by pygmy rabbits. For example, Red Willow
Research Inc. (2000, p 6) observed a pygmy rabbit under a conifer near
a main ranch house in Idaho. In Nevada and California, Larrucea and
Brussard (2008b, p. 1639) found 21 percent of historical sites showed
signs of urbanization and still had pygmy rabbits present. White and
Bartels (2002, pp. 7-8) found urban development had impacted 3 of 13
[[Page 60543]]
historical pygmy rabbit locations in Idaho, and no active pygmy rabbit
burrows were found. Janson (2002, p. 32) discovered that one of his
1940's pygmy rabbit study areas was impacted by residential and
commercial development near Cedar City, Utah, when it was revisited in
2001. He reported that his study area had been ``taken over'' by
development and no pygmy rabbits or recent sign was seen.
The petitioners contend that power lines and fences associated with
urban and rural development result in loss of pygmy rabbit habitat,
predation, displacement, and creation of movement barriers to pygmy
rabbit populations. The available information does not document that
power lines or fences are causing these impacts to pygmy rabbit
populations.
Estes-Zumpf and Rachlow (2009, p. 367) found that several radio-
collared pygmy rabbits crossed gravel roads and creeks in Idaho.
Rauscher (1997, p. 14) reported the use of a subnivian (layer between
snow and soil surface) tunnel that extended across a back country road
near Badger Pass, Montana. Western EcoSystems Technology, Inc. (2008,
p. 28) reported observations of pygmy rabbits crossing open areas,
including desert grasslands with limited shrub cover, roads, and
between shrub lands surrounded by grasslands in Wyoming. These few
studies indicate that roads do not significantly affect pygmy rabbit
movements.
Summary of Urban and Rural Development Impacts
Although loss of sagebrush habitat due to development has been
documented and will continue in the future, the amount of suitable or
occupied pygmy rabbit habitat lost (or the magnitude of that loss
across the range) is minimal in scale compared to overall sagebrush
habitat and will likely remain so. Based on the best available
information, pygmy rabbits have been reported to have been impacted by
some development in a few site-specific areas in Idaho and Utah, but
they have also continued to be present in some other areas. The scope
of loss or modification of sagebrush habitat in general due to urban
and rural development does not equally relate to the loss or
modification of pygmy rabbit habitat because pygmy rabbits are patchily
distributed across the landscape.
While power lines, fences, and roads associated with development
are also known to occur across sagebrush habitat within the range of
the pygmy rabbit, we have no information regarding the amount of pygmy
rabbit habitat that has been impacted across the range. The best
available scientific information does not indicate that power lines,
fences, and roads are threats to the pygmy rabbit. We do not have
reports of raptors associated with power lines or fences impacting
pygmy rabbit populations. The best available scientific information
indicates that pygmy rabbits will cross roads, suggesting roads may be
less of a barrier to pygmy rabbit movements than previously thought.
Therefore, based on the best available scientific and commercial
information, we conclude that urban and rural development, including
associated power lines, fences, and roads, in the sagebrush ecosystem
are not significant threats to the pygmy rabbit now or in the
foreseeable future.
Mining
Sagebrush habitat throughout the west has been impacted by gold,
coal, and uranium mining (Braun 1998, pp. 5-6). Mining, livestock
grazing, and ranching are decreasing as a percent of the economics in
some parts of the western United States (Hansen et al. 2002, 2005 cited
in Knick et al. in press, p. 56). Immediate impacts from mining to
sagebrush habitat include direct loss from mining and construction of
associated facilities, roads, and power lines (Braun 1998, pp. 5-6). In
western North America, development of mines and energy resources began
before 1900 (Robbins and Wolf 1994, cited in Braun 1998, p. 5).
While comprehensive information on the number or surface extent of
mines across the range of the pygmy rabbit is not known, the
development of mineral resources is occurring on a large-scale and
important to the economies of a few of the states in the range. For
example, Nevada ranked second in the United States in terms of value of
overall nonfuel mineral production in 2006 (U.S. Geological Survey
2007, p. 10); Wyoming is the largest coal producer in the U.S. (Wyoming
Mining Association 2008, p. 2).
Between 2006 and 2007, surface coal production increased by 1.6
percent in Wyoming (EIA, http://www.eia.doe.gov/cneaf/coal/page/acr/
table1.pdf, accessed October 19, 2008). The number of Wyoming coal
mines increased from 19 in 2005 to 23 in 2007 (Wyoming Mining
Association 2005, p 5; 2008, p. 6). Most of these mines are located in
the Powder River Basin (Wyoming Mining Association 2008, p. 2) which is
not within the known range of the pygmy rabbit in that State.
Possible impacts from mining to pygmy rabbits could include injury
or death, loss or reduction of forage or shelter, temporary or
permanent home range abandonment, increased habitat fragmentation,
increased dispersal barriers, increased predation, and population
declines. Red Willow Research Inc. (2000, p. 6) reported a pygmy rabbit
sighting near the Historical Tallman Pit on the Sawtooth National
Forest, Idaho. The individual was observed entering the rocks and
boulders on the east edge of the pit. In California, pygmy rabbits have
been observed in the area around Bodie, a mining town that was
abandoned in the mid 1930's (Severaid 1950, p. 2). In Oregon, two
survey areas supported active pygmy rabbit burrows at inactive
diatomaceous earth mines (BLM 2008d, pp. 3, 6). One pygmy rabbit was
observed at one of the sites (BLM 2008d, p. 6). Still, the best
available scientific information does not indicate whether pygmy
rabbits occupied these areas prior to or during the active mining
period or if the observed individuals colonized or recolonized the
areas after mining activities ceased.
Summary of Mining Impacts
Though mining activities occur within sagebrush habitat, we do not
have an estimate of habitat lost to mining impacts; however the impact
to pygmy rabbit habitat is likely small compared to the overall range
of the species and will likely continue to remain so in the future.
Noted increases in the number of Wyoming coal mines occurred mostly in
the Powder River Basin outside the known range of the pygmy rabbit in
that State. We do have some information that indicates pygmy rabbits
have been observed at specific mining areas in Idaho, California, and
Oregon which may indicate pygmy rabbits are adaptable and can exist
near mining sites or reestablish use of mining areas after mining
activities have ceased. The best available scientific information
indicates that significant loss or modification of habitat and
measureable population decreases due to habitat loss or modification
from mining impacts are not occurring across the range. Therefore,
based on the best available scientific and commercial information, we
conclude that habitat loss or modification due to mining is not a
significant threat to the pygmy rabbit now or in the foreseeable
future.
Energy Exploration and Development
Energy exploration and development of non-renewable resources (oil,
gas, coal) has occurred in sagebrush habitat since the late 1800's
(Connelly et al. 2004, p. 7-38). Energy development and its associated
facilities (well pads, access roads, pipelines, compressor
[[Page 60544]]
stations, pumping stations, and power lines) can impact sagebrush
habitats.
The exploration and development of fossil fuels in sagebrush
habitats has increased recently as prices and demand are spurred by
geopolitical uncertainties and legislative mandates (National Petroleum
Council 2007, pp. 5-7). Legislative mandates include those of the
Energy Policy and Conservation Act of 1975 (EPCA), 42 U.S.C. 6201, et
seq., to secure energy supplies and increase the availability of fossil
fuels. The EPCA was re-authorized and amended by the Energy Policy Act
of 2000, P.L. 106-469, and the Energy Policy Act of 2005, PL 109-58,
mandating inventory of Federal nonrenewable resources, economic
incentives for energy development, identification of impediments to
timely granting of leases and post-leasing development, and increased
development of renewable energy resources (DOE 2005). In addition, the
Energy Policy Act of 2005 mandated designation of federal lands for
energy transport corridors (DOE 2005).
Present and future exploration and development is highly likely to
focus on areas of highest potential return. Pursuant to the EPCA
mandates, the BLM as lead Federal agency for EPCA implementation,
released results in 2003 of the first of a 4-phase survey intended to
identify onshore oil and gas resources. Phases II and III were
published in 2006 and 2008, respectively. Phase III supersedes the
previous phases (DOI et al. 2008, p. 6).
Available EPCA inventories indicate energy resources (oil and gas)
in 11 geological basins within the range of the greater sage-grouse as
identified in the 2006 Conservation Strategy (Stiver et al. 2006, p. 1-
11) for the greater sage grouse. Some of these basins also correspond
with pygmy rabbit range: the Wyoming Thrust Belt of Wyoming, Utah and
Idaho; Southwestern Wyoming Basin including portions of Wyoming and
Utah; and Eastern Great Basin in Nevada, Utah, and Southern Idaho.
We are aware that many land parcels within the range of the pygmy
rabbit are leased for oil and gas development. Oil fields have been
developed in east-central Nevada and western and central Utah. Major
oil and gas production areas occur in eastern Utah, southwest Wyoming,
and central California (USFS 2008a, p. 25). We are aware of a number of
projects related to oil, gas, and coalbed methane production in
sagebrush habitats---most notably in Wyoming---as can be seen from the
following list of NEPA documents:
Final Environmental Impact Statement (EIS) for the Jack Morrow
Hills Coordinated Activity Plan/Proposed Green River Resource
Management Plan Amendment, (BLM 2004a), for Sweetwater, Fremont and
Sublette Counties, Wyoming;
Scoping Notice for South Piney Natural Gas Development
Project, (BLM undated), for Sublette County, Wyoming;
Final Supplemental EIS for the Pinedale Anticline Oil and Gas
Exploration and Development Project, (BLM 2008a), for Sublette County,
Wyoming;
Record of Decision Jonah Infill Drilling Project, (BLM 2006b),
for Sublette County, Wyoming;
Record of Decision EIS for the Atlantic Rim Natural Gas Field
Development Project, (BLM 2007d), for Carbon County, Wyoming;
Finding of No Significant Impact and Decision Record for the
Bitter Creek Shallow Oil and Gas Project, Sweetwater County, Wyoming
(BLM 2005b);
Decision Record, Finding of No significant Impact and
Environmental Assessment for the Copper Ridge Shallow Gas Exploration
and Development Project, (BLM 2003b), for Sweetwater County, Wyoming;
Environmental Assessment, Finding of No significant Impact and
Decision Record for the Pacific Rim Shallow Gas Exploration and
Development Project, Sweetwater County, Wyoming (BLM 2004b);
Record of Decision for White Pine and Grant-Quinn Oil and Gas
Leasing Project, (USFS 2007), for White Pine, Nye, and Lincoln
Counties, Nevada;
Final EIS Greater Deadman Bench Oil and Gas Producing Region,
(BLM 2008b), for Uintah County, Utah.
Currently, pygmy rabbits could be most affected by an energy
resources development concentration in the Southwest Wyoming Basin. For
example, the BLM published the Record of Decision in 2008 for Pinedale
Anticline Project Area in southwest Wyoming (BLM 2008e). The project
description included up to 900 drill pads, including dry holes, over a
10 to 15-year development period (BLM 2008a, p. 4-4). Approximately 250
new well pads are proposed in addition to pipelines and other
facilities (BLM 2008e, p. 36). Total initial direct disturbance acres
for the entire Pinedale project are approximately 25,800 ac (10,400 ha)
with over 18,000 ac (7,200 ha) in sagebrush land cover type (BLM 2008a,
pp. 4-52).
The Jonah Gas Project also occurs in the Pinedale Anticline area of
the Southwest Wyoming Basin. In 2006, the BLM issued a Record of
Decision (BLM 2006b, entire) and a final EIS (BLM 2006c, entire) to
extend the existing project to an additional 3,100 wells and up to
16,200 ac (6,556 ha) of new surface disturbance (BLM 2006c, p. 2-4).
Specific features include: at least 64 well pads per 640 ac (259
km\2\), up to 473 mi (761 km) of pipeline and roads, and 140 ac (56 ha)
of new surface disturbance for ancillary facilities (BLM 2006c, pp. 2-4
to 2-5).
The Pinedale Anticline and Jonah Gas Field Projects as analyzed by
the BLM's EISs are not the only oil and gas development occurring in
Wyoming. According to the Wyoming Oil and Gas Commission completed
wells in Wyoming counties with sagebrush habitats increased from a
total of 37,144 in 2005 to 42,510 in 2007. An additional 6,209
applications for permit to drill were approved from January through
September 2008 in these counties (WOGC 2008, http://wogcc.state.wy.us,
accessed September 29, 2008).
The Ruby Pipeline Project, as proposed, involves the construction
and operation of a 675-mi-(1,086-km)-42-inch (106.7-cm)-diameter
natural gas pipeline. The pipeline would transport natural gas from
western Wyoming, through northern Utah and Nevada, to south central
Oregon (Federal Energy Regulatory Commission (FERC) 2010, pp. 1-2- 1-
3). The project would cross known occupied pygmy rabbit habitat in
Wyoming, Utah, and Nevada (FERC 2010, p. 4-126). Approximately 62 ac
(25 ha) of suitable pygmy rabbit habitat was delineated along the
pipeline route in these three states (FERC 2010, p. 4-147). The
Applicant has committed to minimize impacts to pygmy rabbits by
conducting preconstruction surveys, realignment of portions of the
pipeline to avoid occupied habitat, construction buffers, construction
timing restrictions, and specific re-vegetation activities, among other
commitments (FERC 2010, pp. 4-132; 4-159; 5-9).
Possible impacts to pygmy rabbits due to nonrenewable energy
exploration and development include injury or death, loss of habitat,
habitat fragmentation, dispersal barriers, noise, and disturbance due
to increased human presence. Lance (2008, pp. 5-6) provided information
on oil and gas development in southwestern Wyoming as it relates to
pygmy rabbits. He indicated that the greatest number of wells drilled
to date has occurred in the Pinedale/Jonah fields in southern Sublette
County (Big Piney area south to Granger; in the Overthrust Belt along
the Wyoming/Utah border; the Wamsutter area). While oil and gas
development has been intensive in some portions of
[[Page 60545]]
the pygmy rabbit's predicted range in Wyoming, the majority of the
range has been subjected to scattered oil and gas exploration and/or
development, or no exploration or development at all. The pygmy
rabbit's predicted range in Wyoming is based on a predictive
distribution model that uses habitat variables and confirmed pygmy
rabbit records (sightings) from the Wyoming Natural Diversity database
(Lance 2008, pp. 2-3). Lance (2008, p. 5) estimated that 9,200 oil and
gas wells have been drilled within the predicted range. Based on an
average disturbance of 25 ac (10.1 ha) per well (accounting for pad,
production facility, roads, pipelines, etc.), it was estimated that 4
percent of the predicted range in Wyoming has been disturbed by
conventional oil and gas development.
Coal bed methane development is expected in isolated portions of
the pygmy rabbit's predicted range in Wyoming. The areas potentially
suitable for coal bed methane development include the area around
Atlantic Rim and Baggs in Carbon County, and in the vicinity of Hay
Reservoir in Sweetwater County.
While some power lines may cross habitat occupied by pygmy rabbits,
localized and insignificant impacts are expected given the linear
nature of these projects (Lance 2008, p. 6). Power poles could be used
as perches by avian predators preying on pygmy rabbits; however, as
discussed above, we were not able to find evidence documenting this.
Purcell (2006, pp. 2, 34) expressed concern for loss of sagebrush
communities at energy production sites in Wyoming. Purcell (2006, p.
110) mentioned that oil and gas development in southwestern and south
central portions of Wyoming may contribute to degradation of suitable
areas used by pygmy rabbits due to destruction of sagebrush and sodium
contamination of the soil; and recommended that research be conducted
to determine pygmy rabbit response to these disturbances.
In contrast, two studies indicate energy projects and pygmy rabbits
can co-exist. Hayden-Wing Associates, Inc. (2008b, p. 2) compiled pygmy
rabbit observations of all sign (visuals, burrows and pellets, burrows
only, pellets only) they collected during 1994 to 2007 surveys in
Wyoming. All of their observations were within 109 yd (100 m) of roads
(Hayden-Wing Associates, Inc. 2008b, p. 3). Observations were recorded
in the Continental Divide-Wamsutter and Creston-Blue Gap natural gas
project areas in Carbon and Sweetwater Counties; Moxa Arch natural gas
development area in Lincoln, Uinta, and Sweetwater Counties; Jonah gas
field in Sublette County; and Lake Ridge 3D seismic area in Lincoln
County (Hayden-Wing Associates, Inc. 2008b, p. 2). They recorded 1,151
pygmy rabbit observations (visuals, n=216; burrows and pellets, n=422,
pellets only, n=513) (Hayden-Wing Associates, Inc. (2008b, p. 3). The
majority of observations (50 percent) occurred in Moxa, 26 percent
occurred within the Continental Divide-Wamsutter and Creston-Blue Gap
areas, 17 percent in the Jonah gas field, and 6.5 percent in the Lake
Ridge 3D seismic area (Hayden-Wing Associates, Inc. 2008b, p. 3). They
acknowledge biases with road-based surveys and possible uncertainties
in assigning pellets to pygmy rabbits, but concluded that energy
development and pygmy rabbits do coexist throughout portions of Wyoming
(Hayden-Wing Associates, Inc. 2008b, p. 3). Pygmy rabbit locations were
farther away from well pads, but the analysis, in general, suggests
that pygmy rabbits are capable of tolerating some level of disturbance
(Hayden-Wing Associates, Inc. 2008b, p. 4). The authors suggest that
research needs to be conducted to quantify the mechanisms that affect
pygmy rabbits due to energy development, to understand thresholds at
which negative impacts occur, and to determine ways the industry can
avoid impacting populations (Hayden-Wing Associates, Inc. 2008b, p. 4).
Estes-Zumpf et al. (2009, p. 4) began a pygmy rabbit monitoring
program in the Pinedale Anticline Project Area (PAPA) (359 plots) and
in a neighboring Boulder reference area (85 plots), Sublette County,
Wyoming, in 2009. Surveys confirmed recent or current pygmy rabbit use
at 83 percent of the plots, and there were 120 confirmed pygmy rabbit
sightings across both study areas (Estes-Zumpf et al. 2009, p. 9). The
Boulder reference area contained a greater proportion of active plots
(81 percent) compared to the PAPA (54 percent) (Estes-Zumpf et al.
2009, p. 9). One hundred and twelve plots were surveyed in the PAPA
that occurred within the five oil and gas development areas (Estes-
Zumpf et al. 2009, p. 10). The proportion of active (52 percent) and
recently active (25 percent) plots within the development zone was
similar to the proportion of active (54 percent) and recently active
(26 percent) plots throughout the PAPA (Estes-Zumpf et al. 2009, p.
10). Thirty-two known plots were surveyed inside the development zone
and 19 known plots were surveyed in the remainder of the PAPA; the
proportion of known plots in the development zone that were still
active (88 percent) was similar to the proportion of known plots still
active (74 percent) in the remainder of the PAPA (Estes-Zumpf et al.
2009, p. 10). Only 2 (6 percent) of previously known active plots
within the development zone showed recent, but not current, pygmy
rabbit activity (Estes-Zumpf et al. 2009, p. 10).
Past and present renewable energy development (wind, solar, and
geothermal) in sagebrush habitats could impact pygmy rabbits. Possible
impacts to pygmy rabbits could include injury or death, loss of
habitat, habitat fragmentation, dispersal barriers, noise, and
disturbance due to increased human presence. The Department of Interior
(DOI) and Department of Energy (DOE) (2003, pp. 2-17) assessed the
potential for renewable energy being developed on public lands in 11
western States. This assessment also indicated which BLM planning areas
within these States offered the highest potential for each type of
renewable energy (DOI and DOE 2003, pp. 18-24).
BLM published a Final Programmatic EIS on Wind Energy Development
on BLM-administered Lands in the Western United States (BLM 2005c,
entire). This EIS addresses the environmental, social, and economic
impacts associated with wind energy development on BLM-administered
lands in 11 western States under the direction of increasing renewable
energy production on public lands while minimizing environmental and
socio-cultural impacts (BLM 2005c, p. ES-1). Future proposed wind
energy projects may impact sagebrush habitats, and therefore, pygmy
rabbits within the seven States. The 12-month finding for the greater
sage-grouse (75 FR 13950) provides acreage of sagebrush habitat with
wind energy development potential by Greater Sage-grouse Management
Zone. Selecting those management zones that most appropriately overlap
with the pygmy rabbit range, the estimated percent of sagebrush with
developable wind potential in the species range is 3 to 9 percent
(Greater Sage-grouse Management Zones III, IV, V). Greater Sage-grouse
Management Zone II has 42 percent of sagebrush habitat with developable
wind potential, but this incorporates a much larger area of Wyoming
than is known to be occupied by pygmy rabbits.
Wind development could occur in the future in the eastern portion
of the predicted range in Wyoming; most projects are expected to be
located east of Rawlins, and some may occur between Rawlins and
Wamsutter in pygmy rabbit habitat with localized impacts (Lance 2008,
p. 6).
[[Page 60546]]
Eastern Nevada and the Pinedale area of Wyoming are the areas
within the pygmy rabbit range with good potential for commercial solar
development (EIA 2009e, entire cited in 75 FR 13953). The BLM is
developing a programmatic EIS for leasing and development of solar
energy on BLM lands (75 FR 13953).
Geothermal energy facilities occur in pygmy rabbit range in
California, Nevada, Utah, and Idaho. Geothermal potential occurs across
pygmy rabbit range in the four mentioned states above as well as in
southeast Oregon and west central Wyoming (EIA 2009e, entire cited in
75 FR 13953).
A Programmatic EIS for the Designation of Energy Corridors on
Federal Land in the 11 Western States (DOE 2008) was published in 2008.
This EIS addresses section 368 of the Energy Policy Act of 2005 which
directs the designation of corridors for oil, gas, and hydrogen
pipelines, and electricity transmission and distribution facilities on
Federal lands. Federal agencies are required to conduct environmental
reviews to complete the designation and incorporate the designated
corridors into agency land use and resource management plans or
equivalent plans. This EIS proposes only designation of corridors, and
no environmental impacts are attributed to this action. Section 368
does not require agencies to consider or approve specific projects,
applications for rights-of-way (ROW), or other permits within any
designated corridor nor does section 368 direct, license, or permit any
activity on the ground. Any interested applicant would need to apply
for a ROW authorization and the agency would consider each application
under the requirements of various laws and related regulations (DOE
2008, S-1-S-2). The proposed action would designate more than 6,000 mi
(9,600 km) with an average width of 3,500 ft (1 km) of energy corridors
across the West (DOE 2008, p. S-17). Federal land not presently in
transportation or utility right-of-way is proposed for use in Idaho
(102 mi or 164 km), Montana (149 mi or 240 km), Nevada (373 mi or 600
km), Oregon (253 mi or 407 km), Utah (166 mi or 268 km), Wyoming (70 mi
or 113 km), and California (unclear as miles in existing right-of-way
is greater than miles of proposed corridors) (DOE 2008, p. S-18).
Although we do not have data on how much of the corridor is in
sagebrush habitat within the range of pygmy rabbits, based on the
proposed location, habitat in Wyoming, Idaho, Utah, Nevada, and Oregon
would be most affected.
Summary of Energy Exploration and Development Impacts
Energy (nonrenewable and renewable) exploration and development has
been documented within sagebrush habitat. Pygmy rabbits have been
reported to occur in areas impacted by energy development in Wyoming
and have continued to be present in these areas but with unknown
impacts to population trends and long-term population persistence. The
scope of loss or modification of sagebrush habitat in general due to
energy exploration and development does not equally relate to the loss
or modification of pygmy rabbit habitat because of the pygmy rabbit's
patchy habitat distribution across the landscape. Available information
indicates that significant loss or modification of habitat and
measureable population declines from injuries or mortalities, temporary
home range abandonment or permanent home range shift to adjacent areas,
increased habitat fragmentation, increased dispersal barriers, noise,
or increased human presence due to energy development (nonrenewable and
renewable) are not occurring across the range.
Energy exploration and development is occurring, especially within
a portion of the pygmy rabbit's range in Wyoming. Yet, the available
information does not indicate that this potential threat is negatively
impacting pygmy rabbits. Therefore, based on the best available
scientific and commercial information, we conclude that habitat
degradation and loss due to energy exploration and development is not a
significant threat to the pygmy rabbit now or in the foreseeable
future.
Habitat Fragmentation
Habitat fragmentation is the separating of previously contiguous,
functional habitat components that are used by a particular species.
Habitat fragmentation can result from direct losses that leave
remaining habitat in discontinuous patches or from alteration of
habitat such that the habitat becomes unusable to the species (i.e.,
functional habitat loss). This type of loss can result from
disturbances that change a habitat's successional state or remove one
or more of its habitat functions; barriers that prevent use of suitable
areas; and activities that prevent use of habitat due to behavioral
avoidance. Most extant sagebrush habitat has been altered since
European immigrant settlement of the West (Braun 1998, p. 2; West and
Young 2000, Miller and Eddleman 2001, cited in Knick et al. 2003, p.
614; Connelly et al. 2004, p. 7-1). Sagebrush habitat continues to be
fragmented (Knick et al. 2003, p. 625) through various factors (natural
and anthropogenic) and will into the future. Cumulative effects of
habitat fragmentation have not been quantified over the range of
sagebrush and most fragmentation cannot be attributed to specific land
uses (Knick et al. 2003, pp. 614-616). Review of the human- footprint
intensity within the greater sage-grouse management zones showed that
the Northern and Southern Great Basin and Snake River Plain sage-grouse
management zones contained a greater proportion of low-intensity human
footprint area compared to the range-wide intensity (Leu and Hanser in
press, p. 14). Sage-grouse management zones with a higher proportion of
high-intensity human footprint area (Colorado Plateau, Great Plains,
and Columbia Basin) compared to the range-wide intensity (Leu and
Hanser in press, p. 14) occurred outside of the range occupied by the
pygmy rabbit. Thus, in sage-grouse management zones, the range of the
pygmy rabbit occurs mostly within a low-intensity human footprint area.
In general, habitat fragmentation has been mentioned as a potential
threat to pygmy rabbits by several researchers (White and Bartels 2002,
p. 13; Bartels 2003, p. 99; Roberts 2003a, p. 9). Potential impacts to
pygmy rabbits include loss of habitat, increased dispersal distance,
increased predation, and increased isolation. Weiss and Verts (1984, p.
570), in Oregon, stated that fragmentation of sagebrush posed a threat
to pygmy rabbit populations by reducing the size of this vegetative
community and increasing the distances between suitable areas; however,
the severity of this threat to pygmy rabbits cannot be adequately
assessed without improved understanding of the dispersal abilities of
this species and minimum sagebrush patch size requirements. Katzner and
Parker (1997, p. 1071) stated that fragmentation of habitat can
influence size, stability, and success of pygmy rabbit populations
because of their low dispersal capabilities. However, subsequent
studies by researchers, as indicated below, demonstrate dispersal
capabilities of pygmy rabbits are greater than initially thought and
that potential barriers such as perennial creeks and roads do not
appear to be barriers to gene flow among some populations.
Pygmy rabbits depend on sagebrush, but there is no information
available to indicate minimum sagebrush patch size required to support
populations. In Washington, the Service (2007, p. 54) estimated that a
subpopulation of at least 500 Columbia Basin DPS pygmy
[[Page 60547]]
rabbits would need an area of between 454 and 3,250 ac (184 and 1,316
ha) of suitable habitat. Some studies indicate that pygmy rabbit
populations may not be as isolated as previously thought. This has
implications for recolonization and genetic exchange between nearby
areas. In Montana, movement data has shown pygmy rabbits will cross
relatively small open areas (1,500 ft (457 m)) to reach suitable
habitat (Rauscher 1997, p. 5). In Wyoming, Katzner and Parker (1998, p.
73) reported a pygmy rabbit traveled long-distance (2.2 mi (3.5 km))
through open habitat likely unsuitable for long-term habitation. In
Idaho, Estes-Zumpf and Rachlow (2009, p. 367) found median dispersal
movements of 0.93 mi (1.5 km) and 3.9 mi (6.2 km) and maximum dispersal
movements of 4.0 mi (6.5 km) and 7.4 mi (11.9 km) by male and female
juvenile pygmy rabbits, respectively. Crawford (2008, p. 54) in Nevada
and Oregon reported that 24 radio-marked rabbits moved greater than 0.3
mi (0.5 km) with a maximum long-distance movement of 5.3 mi (8.5 km)
recorded by a juvenile female.
Continued survey efforts in recent years have found new populations
throughout the pygmy rabbit's range. Rachlow and Witham (2006, p. 6)
found that the locations of the 32 new sites in the Camas Prairie of
south central Idaho indicated the possibility that movement can occur
among several of these sites. The sites are separated by distances of
less than 3.1 to 4.3 mi (5 to 7 km) which are within dispersal
capabilities shown by Estes-Zumpf and Rachlow (2009) and Rachlow and
Witham (2006, p. 6). Because most surveys for pygmy rabbits are limited
to a single state, it is noteworthy that some reports mention occupied
sites near state lines. This suggests the possibility that additional
unreported genetic exchange may be occurring where ranges overlap two
states. This would further reduce the concern of habitat fragmentation
and isolation. Roberts (2003a, p. 9) reported that 6 of the 9 active
burrow systems found were within 15 mi (24.1 km) of the Idaho State
line. One was within 3 mi (4.8 km) of the Montana border at the head of
Medicine Lodge Creek, Clark County. Two active burrow sites were within
8 mi (12.9 km) of both Wyoming and Utah borders on Pegram Creek, Bear
Lake County. One active burrow site found on the Curlew National
Grasslands was about 15 mi (24.1 km) north of the Utah border and two
active burrows sites were about 15 mi (24.1 km) north of the Nevada
border near Riddle, Idaho. In Montana, Hendricks et al. (2007, p. 13)
mentioned that two new active sites found during their survey occurred
in gaps between other locations and suggested pygmy rabbits may exist
in additional locations in Big Hole Valley. Continued occupancy of
previously known locations along the east side of Big Hole Valley may
benefit through connectivity with populations in Grasshopper Valley,
Argenta Flats, and Horse Prairie located to the south.
Estes-Zumpf et al. (2010, p. 212) obtained genotypes for 249 pygmy
rabbits from 8 sample locations in Lemhi Valley (5) and Camas Prairie
(3), Idaho. They did not document strong evidence of genetic
substructure based on nuclear microsatellites among pygmy rabbit
populations within the study areas (Estes-Zumpf et al. 2010, p. 215).
Lack of strong population structure within the study areas indicates
that perennial creeks and roads do not appear to create substantial
barriers to gene flow (Estes-Zumpf et al. 2010, pp. 215-216). Levels of
genetic diversity in pygmy rabbits were relatively high in the study
areas (Estes-Zumpf et al. 2010, pp. 214). Sample locations within 8.1
mi (13 km) of one another in each study area showed sufficient gene
flow to constitute single populations (Estes-Zumpf et al. 2010, pp.
215).
In Utah, Flinders (2007, pp. 2-3) found fairly extensive
populations in Hamlin Valley located on the Utah/Nevada border in Iron
and Beaver Counties (Utah). He thought that this area may provide an
important habitat corridor between the two States as he found pygmy
rabbit use for several miles on both sides of the border.
Summary of Habitat Fragmentation Impacts
Although we cannot estimate the amount of suitable or occupied
pygmy rabbit habitat lost or the magnitude or extent of that loss due
to habitat fragmentation, the habitat used by pygmy rabbits is
naturally fragmented and populations occur in a patchy distribution
across their range. Because of this patchy habitat distribution across
the range, the scope of loss or modification of sagebrush habitat in
general due to fragmentation does not equally relate to the loss or
modification of pygmy rabbit habitat. Naturally fragmented sagebrush
habitat occupied by pygmy rabbits may not have been more prevalent or
more contiguous prior to human settlement. Local distribution of this
habitat and the distribution of the pygmy rabbit likely shifts over
time due to disturbances from factors such as fire, agriculture
production, flooding, grazing, and weather patterns.
Pygmy rabbit populations may be less isolated than previously
thought based on studies in Idaho, Montana, Wyoming, Nevada, and Utah.
For example, studies related to movement data indicate pygmy rabbits,
including juveniles, can move greater distances than initially thought
(Green and Flinders 1979, p. 88; Gahr 1993, p. 108; Katzner and Parker
1998, p. 73; Crawford 2008, p. 54; Estes-Zumpf and Rachlow 2009, p.
367).
Other studies by Rachlow and Witham (2006, p. 6) and Roberts
(2003a, p. 9) in Idaho, Hendricks et al. (2007, p. 13) in Montana, and
Flinders (2007, pp. 2-3) in Utah, as detailed above, suggest
connectivity may occur among several areas and between states.
Understanding dispersal capabilities of pygmy rabbits plays an
important role in addressing the possibility for genetic exchange among
occupied sites as well as determining whether the characteristics of a
metapopulation apply to this species.
The best available scientific information does not indicate that
fragmented sagebrush habitat is negatively impacting pygmy rabbit
populations across their range. Available information indicates through
genetic analysis that current habitat sagebrush distribution does not
appear to affect dispersal distances, predation, or isolation among
pygmy rabbit populations. Although the necessary patch size to support
pygmy rabbit populations has not been determined, this species has been
reported to historically survive in a naturally fragmented habitat.
Survey efforts demonstrate that pygmy rabbits have been found in areas
impacted or fragmented by various potential threats as discussed in
Factor A and continue to exist in or adjacent to many of these areas
suggesting that habitat fragmentation is not a significant threat to
this species. While its habitat may be impacted to some degree by
current habitat fragmentation, based on the best available scientific
and commercial information, we conclude that habitat fragmentation is
not a significant threat to the pygmy rabbit now or in the foreseeable
future.
Habitat Manipulation Conducted to Benefit Greater Sage-Grouse
There has been a recent and widespread interest in the protection
and restoration of sagebrush habitats with an emphasis on greater sage-
grouse conservation (BLM 2004c). It is uncertain whether efforts
implemented to improve greater sage-grouse habitat will benefit pygmy
rabbits. Some habitat manipulation to benefit greater sage-grouse could
benefit pygmy rabbit (e.g.,
[[Page 60548]]
pinyon-juniper removal) (Larrucea 2007, p. 127).
Connelly et al. (2000, pp. 977, 980) recommend managing sagebrush
canopy cover for greater sage-grouse habitat at 10 to 25 percent for
brood-rearing, 15 to 25 percent for breeding habitat, and 10 to 30
percent for winter habitat. Pygmy rabbits, in general, prefer taller,
denser sagebrush cover relative to the surrounding landscape (Green and
Flinders 1980b, p. 138; Weiss and Verts 1984, p. 567), which can be
greater than the 10 to 30 percent range suggested for greater sage-
grouse habitat needs during their various life history stages. Burak
(2006, pp. 63-64) found total shrub cover values ranged from 41 to 67
percent and sagebrush cover values ranged from 12 to 60 percent in
areas occupied by pygmy rabbits. Reducing dense sagebrush cover to
benefit greater sage-grouse may be in conflict with habitat needs of
pygmy rabbits.
In Nevada, Larrucea (2006, p. 7) raised a concern that sagebrush
management plans which target areas of mature sagebrush for treatment
to promote succession (e.g., Greater Sage-Grouse Conservation Plan for
Nevada and Eastern California (NDOW 2004), cited in Larrucea 2006, p.
7) do not protect pygmy rabbit habitat. The goal of these plans is to
create a mosaic of sagebrush stands of differing ages. These plans
allow for mature sagebrush at the end of the succession, but pygmy
rabbits use their burrows over many seasons and require stable, long
lasting, mature sagebrush. Larrucea (2006, p. 7) suggested a
modification of these plans which would allow protection of habitat for
pygmy rabbits and recommends either: 1) surveying for areas to be
managed for pygmy rabbit habitat; or 2) specifying areas of mature,
clumped, larger than average sagebrush stands within the area to be
managed and taking a portion of these areas to be mapped and managed as
stable, mature sagebrush sites with no treatments applied. The
combination of these two actions (successional and stable) would create
a mosaic of ages. This would incorporate both the succession desired by
other plans while protecting the stable type of habitat needed by pygmy
rabbits. The stable, mature sagebrush would be available for
colonization and the earlier successional stages would be available for
pygmy rabbit dispersal. These untreated areas of late-successional
sagebrush should be included in the actively managed rotational-
successional plan (i.e., NDOW 2004). Larrucea (2006) does not provide
details of any specific project implemented within sagebrush habitats
to improve greater sage-grouse habitat and its possible impact to pygmy
rabbits or their populations.
Summary of Habitat Manipulation Conducted to Benefit Greater Sage-
Grouse
Sagebrush habitat manipulations to benefit greater sage-grouse have
occurred within the range of the pygmy rabbit. Habitat manipulation to
benefit greater sage-grouse or other species was raised as a concern by
the petitioners and a researcher, but the available information does
not provide an example of the effects of this activity on pygmy
rabbits. Additionally, the available information does not indicate
there has been a systematic or widespread loss of habitat due to
habitat manipulation that may have been or is suitable habitat for
pygmy rabbits. Because of the pygmy rabbit's patchy habitat
distribution across the landscape, the scope of loss or modification of
sagebrush habitat in general due to habitat manipulation for greater
sage-grouse does not equally relate to the loss or modification of
pygmy rabbit habitat.
Large-scale sagebrush manipulations to benefit greater sage-grouse
may benefit pygmy rabbit. Based on the similarities with sagebrush
treatments discussed earlier, the size and design of the manipulated
area may minimize adverse impacts to pygmy rabbits. If designed
appropriately, these projects may be beneficial to pygmy rabbits by
opening up areas for new vegetation growth or to provide dispersal
areas. Pygmy rabbits have been found in mosaics where large areas of
sagebrush were left intact and remained connected to adjacent sagebrush
or where treated areas were small and travel distances between them
were minimal. Therefore, based on the best available scientific and
commercial information, we conclude that habitat degradation and loss
due to habitat manipulations for other species is not a significant
threat to the pygmy rabbit now or in the foreseeable future.
Conservation Strategies and Actions
All seven States mention the pygmy rabbit in their Comprehensive
Wildlife Conservation Strategies. These strategies confer no regulatory
mechanisms, but indicate that the species or its habitat deserves
special management considerations (Oregon Department of Fish and
Wildlife 2006; Idaho Department of Fish and Game 2005; Montana Fish,
Wildlife & Parks 2005; Wyoming Game and Fish Department 2005;
California Department of Fish and Game 2005; Nevada Department of
Wildlife 2006; Utah Division of Wildlife Resources 2006).
We are not aware of any States implementing conservation actions
specifically for the pygmy rabbit, though we are aware of initiatives
to restore the sagebrush ecosystem within the range of the pygmy
rabbit. For example, the State of Utah Division of Wildlife Resources
launched the Watershed Initiative in 2003 to implement restoration
projects designed to prevent and reverse habitat loss. Emphasis has
been placed on restoration and protection of shrub-steppe and riparian
habitats in Utah due to their importance to a diversity of wildlife
species. Completed, current, and proposed projects within the range of
pygmy rabbit total 35,335 ac (14,300 ha). Monitoring is an important
component to assessing these treatments (Karpowitz 2008, p. 3). In
addition, research is being conducted to address impacts of treatments
for greater sage-grouse, mule deer, and pronghorn on pygmy rabbit
populations. Preliminary results indicate that at least a 131.2 ft (40-
m) buffer should be established between active pygmy rabbit burrows and
treatments. Future designs should also implement a mosaic pattern and
preserve long and wide swaths of undisturbed mature big sagebrush with
corridors of connectivity between all residual stands. All current and
future habitat projects in pygmy rabbit habitat follow these
recommendations (Karpowitz 2008, p. 3). Although it is not known
whether pygmy rabbits are benefiting from these types of habitat
restoration actions across their range, some actions implemented for
other species may benefit pygmy rabbits (e.g., pinyon-juniper removal
for greater sage-grouse) (Larrucea 2007, p. 127).
At the State level, control of invasive plant species is sometimes
encouraged. Some States require landowners to control noxious weeds on
their property, but the types of plants considered to be noxious weeds
vary by state. For example, only Oregon, California, Colorado, Utah,
and Nevada list medusa head as a noxious, regulated weed, but medusa
head can be problematic in other states (e.g., Idaho). Cheatgrass is
not considered an official noxious weed within the range of the pygmy
rabbit. Although we do not know how these regulations affect sagebrush
habitats, States have regulations regarding invasive species in place.
Summary of Conservation Strategies and Actions
All seven States within the range of the pygmy rabbit mention this
species in their Comprehensive Wildlife Conservation Strategies and
indicate
[[Page 60549]]
that the species or its habitat deserves special management
considerations now and in the future. While we are not aware of any
States implementing conservation actions specifically for the pygmy
rabbit, we are aware of initiatives to restore the sagebrush ecosystem
within the range of the pygmy rabbit over time. Many states encourage
the control of invasive plant species. Conservation strategies and
actions carried out in consideration of the pygmy rabbit will benefit
it now and in the future.
Therefore, based on the best available scientific and commercial
information, we conclude that conservation strategies and actions for
pygmy rabbits or their habitat do not pose a significant threat to the
pygmy rabbit now or in the foreseeable future.
Summary of Factor A
We have assessed the best available scientific and commercial data
on the magnitude and extent of the impacts of agriculture, sagebrush
treatment, livestock grazing, nonnative and invasive plant species,
fire, urban and rural development (and associated facilities), mining,
energy exploration and development (and associated facilities), habitat
fragmentation, greater sage-grouse conservation actions and other
conservation actions on pygmy rabbit habitat. We find that these
threats do not significantly, either singly or cumulatively, impact the
pygmy rabbit to such an extent within the foreseeable future such that
listing under the Act as an endangered or threatened species is
warranted. While sagebrush habitat loss and fragmentation has occurred
within the range of the pygmy rabbit due to various anthropogenic and
natural activities as discussed above and likely will continue at some
level in the future; our review of the best available information
reveals only a handful of specific areas where sagebrush loss or
degradation is occurring in occupied pygmy rabbit habitat. Due to the
pygmy rabbit's patchy habitat distribution across the landscape, the
scope of loss or modification of sagebrush habitat in general does not
equally relate to loss or modification of pygmy rabbit habitat. The
activities listed above are likely to continue into the future with
some increases occurring. However, pygmy rabbit populations continue to
occur throughout the species' current known range, including
historically occupied locations, and some new populations have been
found in recent years, despite numerous activities occurring within its
habitat.
We conclude that the best scientific and commercial information
available indicates that the pygmy rabbit is not now, or in the
foreseeable future, threatened by the present or threatened
destruction, modification, or curtailment of its habitat or range to
the extent that listing under the Act as an endangered or threatened
species is warranted at this time.
Factor B: Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
We have no information that the pygmy rabbit is being used for
commercial or educational purposes.
Hunting
Impacts due to hunting include injury or death with the potential
for impacting population numbers. Some individuals have suggested that
pygmy rabbits were not readily hunted in the past. Bailey (1936, p.
112) indicated an individual from Nevada reported that pygmy rabbits
were not eaten by locals because of the strong sage taste. Later
Larrison (1967, p. 64) said, ``[Pygmy rabbits] flesh tastes of
sagebrush, rendering it unfit as food.''
In Idaho, Fisher (1979, p. 29) recommended that bag limits be
monitored, especially where habitat was declining, because with the
pygmy rabbit's lower reproductive potential as compared to other
rabbits, fewer surplus animals may be available to hunters. Sanchez
(2007, p. 90) reports of an illegal harvest of two pygmy rabbits in her
Idaho study area during 2004 to 2005. Rauscher (1997, pp. 10-11)
reported pygmy rabbit hunting in southwestern Montana, but stated that
hunting did not appear to be a significant mortality factor. Williams
(1986, p. 52) stated that although hunting impacts were not known in
California, he thought that hunters probably did not kill many pygmy
rabbits because the species was quite secretive and rarely left dense
brush. Pritchett et al. (1987, p. 231) reported that, according to
locals near Loa, Wayne County, Utah, pygmy rabbits have been
``extensively hunted'' along with black-tailed jackrabbits (Lepus
californicus) and cottontails. Where he was able to access portions of
his previous study area outside Cedar City, Utah, Janson (2002, p. 32)
found spent shotgun shells. He thought it was probable that some pygmy
rabbits were shot because most hunters cannot distinguish between pygmy
rabbits and cottontails.
We are aware that rabbit drives occurred (Bacon et al. 1959, p.
281; Jackman and Long 1964, p. no page number), but there is little
documentation on the impacts to pygmy rabbits. For example, Bacon et
al. (1959, p. 281) collected rabbits, mostly by organized drives of
hunters who shot them, to gather ectoparasitic (parasite on outer
surface of an animal) information on wild rabbits and rodents in
eastern and central Washington between 1951 and 1956; of the 1,040
rabbits collected, representing four species, only one was a pygmy
rabbit. It is unknown if the single collection indicates pygmy rabbits
are less vulnerable to drives or if numbers were reduced in that area
at the time.
Jackman and Long (1964, p. no page number) documented, with a
photograph, that a rabbit drive occurred in Oregon in 1911. The drive
resulted in 1,811 rabbits being captured, but the species of rabbits
were not identified nor was the location of the drive. The photograph
is courtesy of the Schminke Museum, Lakeview, Lake County, Oregon, so
the drive could have occurred in that county. We do not have any
additional information on rabbit drives occurring within the range of
the pygmy rabbit.
Currently, only three (California, Nevada, and Montana) of the
seven States within the species range allow hunting of pygmy rabbits.
For these States, the State Wildlife Boards of Commissioners set
hunting regulations yearly. In California, for the 2009 to 2010 Upland
Game Season, hunting of pygmy rabbits is allowed from July 1 to January
31 with a bag limit of 5 per day and 10 in possession (California
Department of Fish and Game 2010, http://www.dfg.ca.gov/regulations/09-
10-upland-sum.html, accessed July 20, 2010). The 2009-2010 pygmy rabbit
hunting season in Nevada opened October 10 and closed February 28 with
a daily limit of 10 and a possession limit of 20 (Nevada Department of
Wildlife, 2009, no page numbers). For Montana, the pygmy rabbit is
considered a nongame species and there is no protection from hunting.
Pygmy rabbits can be hunted year-round with no bag limits (Montana
Department of Fish Wildlife and Parks 2010, http://fwp.mt.gov/
wildthings/livingWithWildlife/rabbits/rab_ctrl.html). For these three
States, harvest data are collected through hunter surveys but the
various rabbit species are not distinguished from one another so the
number of pygmy rabbits harvested in these States per year is not
known.
Summary of Hunting Impacts
While it has been reported that pygmy rabbits have been hunted over
the years and specifically in Idaho, Nevada, and Utah, only three
(Montana, California,
[[Page 60550]]
and Nevada) of the seven States within the range of the pygmy rabbit
currently allow hunting of this species. Historical harvest records are
not available, but information indicates a reluctance to eat pygmy
rabbits due to their strong sage taste as well as difficulty in hunting
them due to their secretive nature. The number of pygmy rabbits taken
more recently through hunting is not discernable because of the method
by which present-day data are collected in States that allow hunting.
Based on the best scientific information available, we conclude that
hunting is not a significant threat to the pygmy rabbit now or in the
foreseeable future.
Research
Research activities on pygmy rabbits that involve trapping,
handling, and holding them for a period of time can result in mortality
from exposure, injury, trap predation, intra-specific fighting, and
capture stress (Bailey 1936, pp. 111-112; Severaid 1950, p. 2; Wilde
1978, p. 96; Gahr 1993; Rauscher 1997, p. 9). Mortality rates for
captured pygmy rabbits have been reported as 3 percent (Gahr 1993, p.
37), 5 percent (Wilde 1978, p. 96), and 19 percent (Rauscher 1997, p.
9). Individuals may be killed for specimen collections (Grinnell et al.
1930, pp. 553-555; Bailey 1936, p. 111; Severaid 1950, p. 2).
Investigations may also involve digging out burrows, stepping on
burrows accidentally, measuring vegetation and other site
characteristics near burrows, and other general disturbance in the
study area (Janson 1946, p. 69; Bradfield 1974, pp. 17, 21-22, 26;
Green 1978, pp. 4-6; Gahr 1993, pp. 54-60; Katzner 1994, pp. 6-12;
Rauscher 1997, pp. 6, 12). Katzner (1994, p. 111) reported that all of
his collared rabbits (10) died. He suggested the weight of the radio
collars, and increased grooming as a result of their presence, may have
increased a rabbits' vulnerability to predation. Rachlow and Witham
(2004a, p. 3) reported 1 pygmy rabbit mortality out of the 15 trapped
during their survey efforts. The trap contained a long-tailed weasel
(Mustela frenata), and it was unclear if the weasel killed the rabbit
prior to entering the trap, entered the trap after the rabbit was
captured in the trap, or entered the trap with the rabbit
simultaneously. Sanchez (2007, p. 90) reported two deaths related to
her study due to collars entrapping the lower jaw of the pygmy rabbit.
Flinders et al. (2005, p. 36) captured two pygmy rabbits, placing
radio-collars and ear tags on them. They reported one died due to a
loose collar; the other bit the collar off but was captured by a remote
camera 339 yd (310 m) away from the initial capture site.
Summary of Research Impacts
The documented mortalities due to research activities are
relatively few in number, occur in limited areas, and occur over
limited time periods. Most of these reported mortalities are documented
in studies conducted before 1997 and few mortalities have been reported
in recent documents. Therefore, based on our review of the best
available scientific information, we conclude that research activities
are not a significant threat to the pygmy rabbit now or in the
foreseeable future.
Summary of Factor B
Currently only three States allow hunting of pygmy rabbits; this is
a reduction from the historic condition where all of the states
considered in this finding allowed hunting. We found no data regarding
long-term historical or recent hunting data that would clarify past or
current hunting pressure on the pygmy rabbit across its range. While
there is a potential for populations at low levels to be harmed by
hunting and poaching mortality, our review of the best scientific and
commercial information indicates hunting is not a significant threat to
the pygmy rabbit.
Research activities have been a source of mortality for pygmy
rabbits, although our review of the best scientific information
suggests this is a very minor level of mortality and does not pose a
significant threat to the species.
We have assessed the best available scientific and commercial data
on the magnitude and extent of the impacts of hunting and research
activities on pygmy rabbits. Based on that information, we conclude
that the best scientific and commercial information available indicates
that the pygmy rabbit is not now, or in the foreseeable future,
threatened by the overutilization for commercial, recreational,
scientific, or educational purposes to the extent that listing under
the Act as an endangered or threatened species is warranted at this
time.
Factor C: Disease or Predation
Disease
Possible effects of disease include weakening of individuals which
may increase their vulnerability to predation. Serious disease
outbreaks can impact population size and number. Pygmy rabbits
reportedly can harbor high parasite loads (Janson 1946, p. 90; Wilde
1978, p. 107; Gahr 1993; WDFW 1995; 66 FR 59734). These parasites
include ticks (e.g., Dermacenter paramapterus, D. anersoni,
Haemaphysalis leporis-palustris), fleas (e.g., Cediopsylia inaequalis,
Odontopysilys dentatus), lice (not specified), and bot flies (e.g.,
Cuterebra maculata) (Davis 1939, p. 365; Janson 1940, pp. 25-27; Janson
1946, p. 90; Larrison 1967, p. 64; Wilde 1978, pp. 13-16; Gahr 1993;
Rauscher 1997, p. 12) which can be vectors of disease.
Plague and tularemia can be found in leporid populations, but they
have not been confirmed in pygmy rabbits. Plague is a bacterial disease
that is transmitted by fleas infected with the bacterium, Yersinia
pestis. Tularemia is caused by the bacterium Francisella tularensis and
is commonly transmitted by ticks. These diseases often spread rapidly
and can be fatal (Quan 1993, p. 54). Hall (1946, p. 618), in Nevada,
thought that pygmy rabbits were killed by tularemia based on his
general observations which were not specified. Gahr (1993, p. 22) found
bot flies on two pygmy rabbits located in the grazed area of her study
in Washington, indicating cattle may act as a vector for spreading
parasites and possibly disease. She commented that parasitism by bot
flies is not necessarily detrimental to the rabbit, and additional
study is needed to determine if cattle presence increases the incidence
of ectoparasites for pygmy rabbits.
Red Willow Research Inc. (2002, p. 108) expressed concern that the
transport and transmission of diseases by domestic livestock to pygmy
rabbits could be a threat. Red Willow Research Inc. (2002, p. 108)
raised the concern that a calicivirus, such as Rabbit Hemorrhagic
Disease (RHD), could explain declines in pygmy rabbit populations and
suggests additional research is needed. The Committee for the High
Desert et al. (2003, p. 150) indicated that West Nile Virus is a
growing concern for native wildlife, including pygmy rabbits. We have
no reports of disease epizootics (outbreaks) occurring in pygmy rabbits
in the range considered in this finding. Janson (2002, p. 30) did not
observe any obviously diseased pygmy rabbits in his earlier work in the
1940's. Oliver (2004, p. 36) reported that in Utah, the effects of
parasites and disease on pygmy rabbit populations are not known.
Parasites and disease have not been regarded as a major threat to pygmy
rabbits (Wilde 1978, p. 141; Green 1979, p. 25). The final rule for the
Columbia Basin DPS pygmy rabbit indicated disease, including plague,
was a significant potential threat to the remaining, small populations
(68 FR 10405). A number of captive Columbia Basin pygmy rabbits have
died of mycobacteriosis and
[[Page 60551]]
coccidiosis (WDFW 2005a; Harrenstien et al. 2006 cited in Service 2007,
p. 21). It is unclear if these two diseases were introduced into the
captive breeding population from wild caught individuals or by some
other means. Mycobacteriosis and coccidiosis have not been reported in
pygmy rabbits occurring in the rest of its range.
Summary of Disease Impacts
Though pygmy rabbits can harbor high parasite loads, there is no
evidence that this is negatively impacting pygmy rabbit populations.
Through our review of the best scientific and commercial information we
found no reports of disease epizootics occurring in pygmy rabbit
populations anywhere within the range of the species. Therefore, based
on our review of the best available information, we conclude that
disease is not a significant threat to the pygmy rabbit now or in the
foreseeable future.
Predation
Predation of pygmy rabbits has been reported in Idaho, Nevada, and
Utah. According to Green (1979, p. 25) predation is the main cause of
pygmy rabbit mortality. The annual mortality rate of adult pygmy
rabbits may be as high as 88 percent, and one researcher found that
more than 50 percent of juveniles can die within about 5 weeks of their
emergence (Wilde 1978, pp. 139-140). Estes-Zumpf and Rachlow (2009, p.
367) found mortality rates were 69 percent and 88.5 percent for male
and female juvenile pygmy rabbits, respectively, in their study area in
east-central Idaho. The mortality rate was highest within two months of
emerging from the natal burrow. However, mortality rates for adult and
juveniles can vary considerably between years and for juveniles between
cohorts within years (Wilde 1978, pp. 85-95, 138-140).
While pygmy rabbits have numerous predators, they have adapted to
their presence (Janson 1946, pp. 28-29; Gashwiler et al. 1960, p. 227;
Green 1978, p. 37; Wilde 1978, pp. 141-143). Junipers provide perches
for avian predators and may provide habitat for mammalian predators
(Larrucea and Brussard 2008b, p. 1640). However, Larrucea and Brussard
(2008b) do not provide actual losses of pygmy rabbits to predators
utilizing pinyon-juniper habitat. If levels of predation are too high,
local populations may be suppressed below a point at which they can be
maintained. Sagebrush habitat with damaged structural components may
increase the pygmy rabbit's vulnerability to predation. Weiss and Verts
(1984, p. 569) thought that use of denser and taller sagebrush habitats
by pygmy rabbits was related to predator avoidance. Katzner (1994, p.
52) documented that raptors were a cause of mortality and denser
sagebrush cover deterred these avian predators. In Idaho, Sanchez
(2007, pp. 90-91) attributed 42 percent of natural mortalities to
mammalian and avian predation; the cause of death in 58 percent of the
mortalities could not be determined.
Summary of Predation Impacts
Pygmy rabbits are a prey species and predation has been stated by
some researchers as the main cause of mortality. Annual mortality rates
for adult and juvenile pygmy rabbits can be high, but these rates can
vary considerably between years and between juvenile cohorts within
particular years. Predation is a natural part of population dynamics
for any species and results in the death of individuals. Based on our
review of the best available scientific information, we did not find
any indication of predation being a significant threat to the pygmy
rabbit in all or a significant portion of its range. The Service is not
aware of any predators that potentially pose a significant threat to
the species. We therefore conclude that the available information
indicates that the pygmy rabbit is not threatened by predation now or
in the foreseeable future.
Summary of Factor C
Disease and predation may be significant threat factors to local or
isolated pygmy rabbit populations; however, based on our review of the
best available scientific information, we did not find any information
to indicate significant threats from either disease or predation
Habitat degradation and fragmentation may increase the effects of
parasites, disease, and predation on some populations. We do not have
any reports indicating that RHD or West Nile Virus is a significant
threat to pygmy rabbits, nor are we are aware of reports of disease
epizootics occurring in wild pygmy rabbits anywhere within the species'
range. Therefore, we conclude that the best scientific and commercial
information available indicates that the pygmy rabbit is not now, or in
the foreseeable future, threatened by disease or predation to the
extent that listing under the Act as an endangered or threatened
species is warranted at this time.
Factor D: Inadequacy of Existing Regulatory Mechanisms
Local Laws and Regulations
We are not aware of any county or city ordinances that provide
protection specifically for pygmy rabbits or their habitat on private
lands. We recognize that county or city ordinances that address
agricultural lands, transportation, and zoning for various land uses
have the potential to influence pygmy rabbits or their habitat (zoning
that protects open space might retain suitable pygmy rabbit habitat; a
housing development and associated roads might destroy or fragment
habitat). We found no detailed information regarding the nature or
extent of zoning efforts within the species' range and its direct or
indirect effects on pygmy rabbit habitat or populations.
State Laws and Regulations
Currently, hunting of pygmy rabbits is allowed in three of the
seven States within the species' range (California, Nevada, and
Montana). In California, for the 2009 to 2010 Upland Game Season,
hunting of pygmy rabbits is allowed from July 1 to January 31 with a
bag limit of 5 per day and 10 in possession (California Department of
Fish and Game, 2010, http://www.dfg.ca.gov/regulations/09-10-upland-
sum.html, accessed July 20, 2010). In Nevada, the 2009-2010 pygmy
rabbit hunting season opened on October 10 and closed on February 28
with a daily limit of 10 and a possession limit of 20 (Nevada
Department of Wildlife, 2009, no page numbers). For Montana, the pygmy
rabbit is considered a species of concern, nongame species and there is
no protection from hunting. Pygmy rabbits can be hunted year-round with
no bag limits (Montana Department of Fish Wildlife and Parks 2010,
http://fwp.mt.gov/wildthings/livingWithWildlife/rabbits/rab_
ctrl.html). Due to the manner of data collection, the numbers of pygmy
rabbits harvested in these States each year is not known.
Hunting of pygmy rabbits is not allowed in Idaho or Wyoming where
they are considered a species of special concern, or in Utah where they
are considered a sensitive species. Nor is hunting allowed in Oregon
where the pygmy rabbit is considered a sensitive species and protected
under State law.
In Wyoming, many oil and gas development projects occurring on
private lands fall under the jurisdiction of the Wyoming Industrial
Siting Act (cited in Lance 2008, p. 6). This requires the Industrial
Siting Administration to consult with Wyoming Game and Fish
[[Page 60552]]
Department to address impacts; and appropriate mitigation is required
prior to issuance of permits (Lance 2008, pp. 5-6). As mentioned above,
monitoring for restoration and mitigation activities are in the early
stages. We do not know whether pygmy rabbits are benefiting from any
mitigation that may have been required under reviewed projects, but
restoration of sagebrush habitat is likely to positively impact pygmy
rabbits.
Summary of State Laws and Regulations Impacts
Hunting of pygmy rabbits is allowed in three of the seven States.
In Wyoming, many oil and gas projects located on private lands will be
reviewed by that state's wildlife agency with appropriate mitigation
required that may benefit pygmy rabbits. The best available information
indicates that the inadequacy of existing State laws do not threaten
the pygmy rabbit.
Federal Laws and Regulations
A large portion of the sagebrush community with the potential to
support pygmy rabbits occurs on BLM lands. The Federal Land Policy and
Management Act of 1976 (FLPMA) (43 U.S.C. 1701 et seq.) is the primary
Federal law governing most land uses on BLM-administered lands. Section
102 (a)(8) of FLPMA specifically recognizes that wildlife and fish
resources are the uses for which these lands are to be managed.
We acknowledge that data to evaluate the effectiveness of BLM's
programs on pygmy rabbit conservation are not available. Whether the
various BLM stipulations issued related to oil and gas activities
specific to the greater sage-grouse (75 FR 13978) also reduce impacts
from these activities to pygmy rabbits and their habitats is unknown.
The BLM has management and permitting authorities to regulate and
condition oil and gas lease permits under FLPMA and the Mineral Leasing
Act (MLA) (30 U.S.C. 181 et seq.). BLM usually incorporates
stipulations as a condition of issuing leases. The BLM's planning
handbook has program-specific guidance for fluid materials (including
oil and gas) that specifies that Resource Management Plan (RMP)
decision-makers will consider restrictions on areas subject to leasing,
including closures, and lease stipulations (BLM 2000, Appendix C, p.
16). The handbook also specifies that all stipulations must have
waiver, exception, or modification criteria documented in the plan, and
indicates that the least restrictive constraint to meet the resource
protection objective should be used (BLM 2000, Appendix C, p. 16).
BLM's RMPs are the basis for all actions and authorizations
involving BLM-administered land and resources. They establish allowable
resource uses; resource condition, goals and objectives to be attained;
program constraints and general management practices needed to attain
the goals and objectives; general implementation sequences; and
intervals and standards for monitoring and evaluating each plan to
determine its effectiveness and the need for amendment or revision (43
CFR 1601.0-5(k)).
RMPs provide a framework and programmatic guidance for site-
specific activity plans. These plans address livestock grazing, oil and
gas field development, travel management (managing vehicle routes and
access), wildlife habitat management, and other activities. Activity
plan decisions normally require National Environmental Policy Act
(NEPA) (42 U.S.C. 4321 et seq.) analysis.
BLM has designated the pygmy rabbit as a special status species/
bureau assessment species in five (Idaho, Montana, Nevada, Oregon, and
Wyoming) of the seven States in which it occurs. BLM policy and
guidance for species of concern occurring on BLM managed land is
addressed under BLM's 6840 Manual, ``Special Status Species
Management'' (BLM 2008c entirety). This manual provides agency policy
and guidance for the conservation of special status plants and animals
and the ecosystems on which they depend, but it is not a regulatory
document. The objectives for BLM special status species are `` to
conserve and/or recover ESA-listed species and the ecosystems on which
they depend so that ESA protections are no longer needed for these
species and to initiate proactive conservation measures that reduce or
eliminate threats to Bureau sensitive species to minimize the
likelihood of and need for listing of these species under the ESA.''
(BLM 2008c, p. 3).
There has been an increased focus on the roles that state, county,
and private entities have in controlling invasive plants. For example,
the Noxious Weed Control and Eradication Act was passed in 2004 and
incorporated into the Plant Protection Act. This Act is intended to
assist eligible weed management entities to control or eradicate
harmful nonnative weeds on both public and private lands. Additionally,
Executive Order 13112 was signed on February 3, 1999, establishing an
interagency National Invasive Species Council in charge of creating and
implementing a National Invasive Species Management Plan. The
Management Plan directs federal efforts, including overall strategy and
objectives, to prevent, control, and minimize invasive species and
their impacts (National Invasive Species Council 2008, p. 5). However,
the Order also directs the Council to encourage planning and action at
local, tribal, state, regional, and eco-system levels to achieve the
goals of the National Invasive Species Management Plan, in cooperation
with stakeholders (e.g., private landowners, states) and existing
organizations addressing invasive species.
Noxious and invasive weed treatments on BLM lands involving
reseeding can occur through the Emergency Stabilization and Burned Area
Rehabilitation Programs. Invasive species control is a stated priority
in many RMPs. For example, 76 of the RMPs included in BLM's response to
a data call claim that the RMP (or supplemental plans/guidance
applicable to the RMP) require treatment of noxious weeds on all
disturbed surfaces to avoid infestations of BLM-managed lands in the
planning area (Carlson 2008a cited in 75 FR 13977). We also note that
it is possible that more RMPs specifically address invasive species
under another general restoration category (75 FR 13977).
BLM commonly uses herbicides on lands to control invasive plant
species. In 2007, the BLM completed a programmatic EIS (BLM 2007c) and
Record of Decision for vegetation treatments on BLM-administered lands
in the western United States. This program approves the use of four new
herbicides, provides updated analysis of 18 currently used herbicides,
and identifies herbicides that the BLM will no longer use on public
lands. Information is unavailable on how frequently the programmatic
EIS has been used for most states or whether actions implemented under
this EIS have been effective; and while not authorizing any specific
on-the-ground actions, it guides the use of herbicides for field-level
planning. Site-specific NEPA analysis is still required at the project
level (BLM 2007c, p. ES-1 to ES-2).
Another voluntary approach to control invasive plant species is the
development of Cooperative Weed Management Areas (CWMAs). CWMAs are
partnerships between federal, state, and local agencies, tribes,
individuals, and interested groups to manage both regulatory noxious
weeds and invasive plants in a county or multi-county geographical
area. They function under a mutually developed memorandum of
understanding and a locally developed
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strategic plan. The CWMAs can utilize federal funds for invasive plant
control on non-federal land. As of 2005, Oregon, Nevada, and Utah had
between 75 and 89 percent of their state covered by CWMAs and/or county
weed districts, while Idaho, Montana, Wyoming, and California had
between 90 and 100 percent coverage (Center for Invasive Plant
Management 2008, www.weedcenter.org/weed_mgmt_areas/wma_
overview.html).
BLM regulatory authority for grazing management is provided at 43
CFR part 4100 (Regulations on Grazing Administration Exclusive of
Alaska). Livestock grazing permits and leases contain terms and
conditions determined by BLM to be appropriate to achieve management
and resource condition objectives on the public lands and other lands
administered by the BLM, and to ensure that habitats are, or are making
significant progress toward being restored or maintained for BLM
special status species (43 CFR 4180.1(d)). Grazing practices and
activities include the development of grazing related portions of
implementation or activity plans, establishment of terms and conditions
of permits, leases and other grazing authorizations, and range
improvement activities such as vegetation manipulation, fence
construction, and development of water for livestock.
BLM grazing administration standards for a particular state or
region must address habitat for endangered, threatened, proposed,
candidate, or special status species, and habitat quality for native
plant and animal populations and communities (43 CFR 4180.2 (d)(4) and
(5). The guidelines must address restoring, maintaining or enhancing
habitats of BLM special status species to promote their conservation,
and maintaining or promoting the physical and biological conditions to
sustain native populations and communities (43 CFR 4180.2(e)(9) and
(10).
Information regarding assessments of rangelands is not available.
During 2004 through 2008, BLM conducted a national data call to collect
information on the status of rangelands, rangeland health assessments,
and measures that have been implemented to address rangeland health
issues under their jurisdiction. The information collected was unusable
to make broad generalizations about the status of rangelands or
management actions because of inconsistency across the range regarding
how questions were interpreted and answered. This limited the ability
to use this information in understanding habitat conditions on BLM
lands (75 FR 13976).
Since 2005, the BLM has developed or is in the process of
developing guidances to minimize impacts of renewable energy production
on public lands. A Record of Decision for ``Implementation of a Wind
Energy Development Program and Associated Land Use Plan Amendments''
was issued in 2005. The Record of Decision outlines the Best Management
Practices for the siting, development, and operation of wind energy
facilities on BLM lands. A final programmatic EIS and Record of
Decision for geothermal development were issued in 2008. The BLM is in
the process of developing programmatic-level guidance for the
development of solar energy projects. The draft programmatic EIS for
solar energy is under development -available at http://www.blm.gov/wo/
st/en/prog/energy/epca_chart.html).
Although we are uncertain which management direction the USFS is
taking for the pygmy rabbit or whether pygmy rabbit habitat objectives
and conservation measures have been incorporated into grazing allotment
plans or Land and Resource Management Plan (LRMPs), the pygmy rabbit is
designated as a USFS Sensitive Species in the Intermountain Region (R4)
(USFS 2008b, p. 1). This includes southern Idaho, western Wyoming,
Utah, and Nevada; the Northern Region (R1) which includes Montana (USFS
2005, p. 2); and the Pacific Northwest Region (R6) which includes
Oregon (USFS 2008c, p. 2). Sensitive species receive special management
to ensure viability and to preclude trends that may lead to the need
for Federal listing. There must be no impacts to sensitive species
without an analysis of the significance of adverse impacts on
populations, habitat and on the viability of the species as a whole
(USFS Manual 2672.1, cited in USFS 2008b, p. 1).
Management of Federal activities on National Forest System lands is
guided principally by the National Forest Management Act (NFMA) 16
U.S.C. 1600-1614, August 17, 1974, as amended. NFMA specifies that all
national forests and grasslands must have a LRMP (16 U.S.C. 1604(a)) to
guide and set standards for natural resource management activities.
NFMA also requires the USFS to incorporate standards and guidelines
into LRMPs (16 U.S.C. 1604(c)). This has historically been done through
a NEPA process. In order to meet overall multiple-use objectives,
provisions are developed to manage plant and animal communities for
diversity, based on the suitability and capability of a specific land
area.
The 1982 NFMA implementing regulations for land and resource
management planning under which all existing forest plans were
prepared, requires the USFS to manage habitat in order to maintain
viable populations of existing native vertebrate species on National
Forest System lands (47 FR 43037, September 30, 1982). A new USFS
planning regulation was published on April 21, 2008 (73 FR 21,468)
which superseded the 1982 rule. Plans developed under the new
regulations would be more strategic and less prescriptive in nature
than those developed under the 1982 planning rule. However, on June 30,
2009, the U.S. District Court for the Northern District of California
vacated the new rule, and as a result, the rule is not currently in use
by the USFS.
Through the NFMA, LRMPs, and the On-Shore Oil and Gas Leasing
Reform Act (1987; implementing regulations at 36 CFR 228, subpart E),
the USFS has the authority to manage, restrict, or include protective
measures to mineral and other energy permits on their lands. Similar to
BLM, existing protective standard stipulations on USFS lands occur for
greater sage-grouse (75 FR 13980). The USFS is a partner agency with
the BLM on the draft programmatic EIS for geothermal energy development
mentioned above. If finalized, the programmatic EIS will amend relevant
LRMPs and will expedite the leasing of USFS lands with geothermal
energy potential.
Pygmy rabbit habitat also occurs on lands managed by other Federal
agencies such as the Service and National Park Service (NPS). The
National Wildlife Refuge System Administration Act (16 U.S.C. 668dd-
668ee) provides guidelines and directives for administration and
management of all areas in the National Wildlife Refuge system. Refuges
are managed for species conservation, consistent with direction in the
National Wildlife Refuge System Administration Act, as amended, and
related Service policies and guidance. The National Park Service
Organic Act (16 U.S.C. Sec. 1, et seq.) states that the NPS will
administer areas under their jurisdiction ``*** by such means and
measures as conform to the fundamental purpose of said parks,
monuments, and reservations, which purpose is to conserve the scenery
and the natural and historical objects and the wildlife within and to
provide for the enjoyment of the same in such manner and by such means
as will leave them unimpaired for the enjoyment of future
generations.''
[[Page 60554]]
Summary of Federal Laws and Regulations Impacts
A large portion of pygmy rabbit habitat occurs on lands
administered by Federal agencies, including BLM, USFS, Service, and
NPS. Numerous policies, guidance, and laws have been developed to
assist the different agencies in management of these lands. The Bureau
of Land Management policies and guidance address species of concern,
actions covered by RMPs, and regulatory authority for grazing and oil
and gas leasing and operating. The USFS policies and guidance address
sensitive species and actions covered by LRMPs. The Service uses
guidelines and directives under the National Wildlife Refuge System
Administration Act for management of lands in the National Wildlife
Refuge system. The National Park Service Organic Act provides
management guidance to the NPS for management of lands administered by
this agency.
As discussed under Factors A and E, the best available information
indicates that activities such as livestock grazing, mining, energy
exploration and development, and recreational activities that are
regulated by various policies, guidance, and laws on Federal lands are
not significantly impacting pygmy rabbits. Therefore, we conclude that
available information indicates that the existence of inadequate
Federal laws and regulations are not a significant threat to the pygmy
rabbit.
Summary of Factor D
Our assessment of threats based on the best available scientific
and commercial data regarding the past, present and future loss or
modification of pygmy rabbit habitat as discussed in Factor A, hunting
activities as discussed in Factor B, and intra and inter-specific
competition or recreational and non recreational vehicle use as
discussed under Factor E lead us to conclude that the inadequacy of
existing regulatory mechanisms is not a threat to the pygmy rabbit.
Therefore, the best available scientific and commercial information
indicates that the pygmy rabbit is not now, or in the foreseeable
future, threatened by the inadequacy of existing regulatory mechanisms
to the extent that listing under the Act as an endangered or threatened
species is warranted at this time.
Factor E: Other Natural or Manmade Factors Affecting the Species
Continued Existence
Several other potential threats have been mentioned as possibly
negatively impacting pygmy rabbit populations including: (1) intra- and
inter-specific competition; (2) small or isolated populations; (3)
natural stochastic (random) events such as floods and drought; (4)
climate change; (5) recreational activities; (6) mortality caused by
collisions with vehicles; and (7) life history traits of a habitat
specialist.
Intra- and Inter-specific Competition
While intra-specific competition likely occurs both under normal
and stressful environmental conditions, we are not aware of any
scientific information documenting or suggesting that such competition
for food and space is negatively impacting pygmy rabbits at this time.
As pygmy rabbits are habitat specialists, inter-specific
competition with other herbivores for sagebrush such as jackrabbits,
pronghorn, and mule deer could occur. Numerous researchers have
mentioned other leporid species, namely black-tailed and white-tailed
(Lepus townsendii) jackrabbits, and mountain cottontails (Silvilagus
nuttallii) as occurring in the same areas with pygmy rabbits throughout
their range.
In Oregon, Anthony (1913, p. 23) mentioned that cottontails and
black-tailed jackrabbits were observed in the same areas with pygmy
rabbits. Bartels (2003, p. 93) also mentioned these two species were
observed in areas used by pygmy rabbits.
In Idaho, Merriam (1891, p, 13) mentioned white- and black-tailed
jack rabbits and mountain cottontails in Pahsimeroi Valley where the
pygmy rabbit also occurred. Roberts (2004, p. 4) mentioned that at one
site in the Birch Creek area he flushed pygmy rabbits along with
cottontails. Waterbury (2006, p. 10) found other rabbit and hare
species (black-tailed and white-tailed jackrabbits, mountain
cottontails) in association with pygmy rabbits in several locations,
including Pahsimeroi and Big Lost River Valleys.
In Montana, Rauscher (1997 p. 11) mentioned mountain cottontails
and jack rabbits were observed at most pygmy rabbit sites. It was
unclear if cottontails and pygmy rabbits were sharing burrows, if
cottontails were replacing pygmy rabbits at burrows, or if cottontails
were taking advantage of burrow availability.
In California and Nevada, Larrucea and Brussard (2008a, p. 697)
found cottontail rabbits may compete with pygmy rabbits and influence
the relationship between understory growth and pygmy rabbit presence.
Cottontails appear to occur more in areas with greater understory
(Larrucea and Brussard 2008a, p. 697). Though pygmy rabbits consume
primarily sagebrush, they will also eat forbs and grasses (Green and
Flinders 1980b, p. 138).
In California, Severaid (1950, p. 4) commented that white- and
black-tailed jackrabbits and cottontails occupied the same habitats as
pygmy rabbits. In northern Utah, Janson (1946, p. 40) also mentioned
that these three species were occupying the same areas as pygmy
rabbits.
Grinnell et al. (1930, pp. 557-558) also noted the overlap of pygmy
rabbit's range with other leporids, namely mountain cottontail and
black-tailed jackrabbit ranges. The other species occurred within or
near the same territories as pygmy rabbits throughout all of their
ranges, but mountain cottontails and black-tailed jackrabbits ranged
over a much larger area than the pygmy rabbit. They suggested that the
differentiation of each is mainly due to conditions outside of the
range of the pygmy rabbit and these conditions may limit the territory
of the pygmy rabbit.
Conde (1982, p. 4) compared pygmy rabbit and black-tailed
jackrabbit use in sagebrush-greasewood habitat in Cassia County, Idaho.
She found in summer that pygmy rabbits selected areas with abundant
grass while jackrabbits selected areas with abundant forbs. During the
fall-winter period shrubs played an important role for both species,
but pygmy rabbits fed on sagebrush leaves and young stems (Johnson
1979, cited in Conde 1982, p. 19) and jackrabbits on 2-year old woody
stems (Currie and Goodwin 1966, cited in Conde 1982, p. 19). Spatial
distribution and exploitation of different vegetation in the summer
allowed a sympatric relationship to occur between these two species
(Conde 1982, p. 3).
Grazing competition with livestock will depend on the range
conditions and grazing practices that vary across the range of the
pygmy rabbit. While researchers have documented pygmy rabbit in
livestock use areas and the potential impacts to pygmy rabbits under
Factor A, we are unaware of studies documenting aspects of potential
forage competition between the two species within the range of the
pygmy rabbit. We are aware of one study conducted at Sagebrush Flat,
Washington, by Siegel Thines et al. (2004, p. 532) that found Columbia
Basin pygmy rabbits selected ungrazed areas over grazed areas when
constructing burrows. Livestock grazing during late summer and fall
reduced the availability of grass (and likely forbs) by about 50
percent in the grazed units until the following growing season. Grasses
provided greater than 50
[[Page 60555]]
percent and forbs greater than 30 percent of the pygmy rabbit's diet in
winter at Sagebrush Flat. They did not find that Columbia Basin pygmy
rabbits ate less grass in grazed areas or that they chose different
diets relative to the availability between ungrazed and grazed areas
before the yearly grazing. However, after yearly grazing the Columbia
Basin pygmy rabbits may have had a harder time finding grasses and
forbs in the grazed areas. Grazing reduced the nutritional quality of
grasses in winter and spring. On grazed areas, grasses had less protein
and more fiber than ungrazed areas. Shrubs were more fibrous in grazed
areas than ungrazed areas in winter. However, grasses may not have been
providing a more nutritious food source for Columbia Basin pygmy
rabbits in winter as they provided about 50 percent less of the crude
protein and 50 percent more fiber than sagebrush or rabbit brush. It is
unclear why the Columbia Basin pygmy rabbits avoided grazed areas and
may not be due to diet-related reasons not measured in the study. Other
impacts of cattle grazing in pygmy rabbit habitat have been previously
discussed under Factor A.
In Montana, there is spatial overlap between big game (elk Cervus
elaphus, mule deer Odocoileus hemionus, antelope Antilocapra americana)
winter range, jack rabbits and greater sage-grouse, and the range of
pygmy rabbits. Hence, inter specific competition with pygmy rabbits may
result (Janson 2002, pp. 16-17).
Summary of Intra- and Inter-specific Competition Impacts
Most authors only mention observing these other rabbit and hare
species while they were studying or searching for pygmy rabbits in
Oregon, Idaho, Montana, California, Nevada, and Utah; few authors
suggest that there is possible competition between or among the species
that negatively impacts pygmy rabbits. One study demonstrates a
sympatric relationship between pygmy rabbits and black-tailed
jackrabbits in Idaho. It has been suggested in Montana that competition
may occur between big game species and pygmy rabbits where they
coexist. While livestock grazing occurs throughout the range of the
pygmy rabbit, its impact on the species remains unclear as discussed
under Factor A. Any possible negative impacts to pygmy rabbits may be
related more to loss or degradation of sagebrush structure as opposed
to loss or reduction of the grass or forbs understory. The best
scientific and commercial information available does not provide any
documentation that pygmy rabbits are adversely affected by intra-
specific competition for food or space across their range. We know from
numerous reports that there appears to be a long history of pygmy
rabbits co-existing across their range, with other species, especially
other rabbit and hare species. The available information does not
document adverse effects of inter-specific competition on pygmy rabbits
from other species of rabbits or hares or other species. Therefore,
based on the best available scientific and commercial information, we
conclude that the intra- or inter-specific competition is a not a
significant threat to the pygmy rabbit now or in the foreseeable
future.
Small or Isolated Populations
Small, restricted populations are more vulnerable to risks and more
susceptible to extinction from naturally occurring stochastic
environmental causes than populations with large numbers occurring over
a large area (Shaffer 1981, pp. 131-132). Small, isolated populations
are also at a greater risk to the deleterious effects of demographic
and genetic problems (Schaffer 1981, p. 133). Random demographic
effects (e.g., skewed sex ratios) and loss of genetic variability may
result in individuals and populations being less able to cope with
environmental change.
As discussed in the Background Section, accurately estimating pygmy
rabbit population size is complex because the number of active burrows
may not be directly related to the number of individuals in a given
area. Some individual pygmy rabbits appear to maintain multiple burrows
and conversely some individual burrows are used by multiple individuals
(Janson 1940, p. 21; Janson 1946, p. 44; Gahr 1993, pp. 66, 68; Heady
1998, p. 25). Pygmy rabbits may also use more than one burrow or burrow
system at a specific time or during different times of the year
(Purcell 2006, p. 96).
It is possible that pygmy rabbits have a metapopulation structure
and therefore, populations located across the range are not small or
isolated because they are able to interact with neighboring populations
if distance is not too great. Recent studies as mentioned in the
Background section above, indicate that pygmy rabbit home ranges and
dispersal capabilities are greater than previously thought. Genetic
research has occurred in some areas of the species' range, and we have
information documenting little population substructure in areas
supporting pygmy rabbit in Idaho indicating these populations are not
isolated (Estes-Zumpf et al. 2010, p. 215).
Summary of Small or Isolated Populations
The impacts of various potential threats can be more pronounced on
small or isolated populations. However, the best available scientific
and commercial information does not indicate that pygmy rabbit
populations are isolated or occurring in small populations across the
range, or that these are significant threats now or in the foreseeable
future.
Stochastic Events
Natural stochastic events can significantly impact populations if
they result in high mortality, habitat loss, or offer little or no
possibility of recolonization. They are most significant for small or
fragmented populations (Gilpin and Soule 1986, p. 25). Flooding which
may cause burrow abandonment, mortality, and erosion of deep soils has
been mentioned as a concern for pygmy rabbits. Pygmy rabbits are known
to use deeper soils found along drainages for their burrows (Flath and
Rauscher 1995, p. 2). Bartels (2003, p. 103) mentions a large flood
event in pygmy rabbit habitat in the Harney Basin, Oregon, in 1984,
though it is not reported if animals were actually killed. Drought can
reduce vegetative cover, potentially resulting in increased soil
erosion and subsequent reduced soil depths, decreased water
infiltration, and reduced water storage capacity (Connelly et al. 2004,
p. 7-19), Pygmy rabbit populations could be impacted directly by loss
of habitat (food and shelter) or indirectly through possible increased
predation. Drought has not been reported as having a direct negative
effect on pygmy rabbits.
Summary of Stochastic Events Impacts
While natural stochastic events most certainly have occurred within
the range of the pygmy rabbit and may have impacted specific
populations, such as in Oregon during a flood, they have not been
documented as types of events that have played a significant role in
population distribution, abundance, and/or trends for the pygmy rabbit
within its range. The best available scientific and commercial
information does not indicate that stochastic events are a significant
threat to the pygmy rabbit now or in the foreseeable future.
Climate Change
The Service acknowledges that environmental changes resulting from
climate change could facilitate invasion and establishment of invasive
species or exacerbate the fire regime, possibly accelerating the loss
of sagebrush habitats (Connelly et al. 2004, p. 7-18).
[[Page 60556]]
Increases in the expansion of pinyon and juniper woodlands in the
Great Basin may have resulted from poor habitat management and climate
change (Connelly et al. 2004, p. 7-7). However, the encroachment of
pinyon-juniper into occupied pygmy rabbit habitat is a slow process,
and pygmy rabbits may be able to inhabit those areas or shift their
home range to adjacent areas if pinyon-junipers habitat becomes
established at a site.
One researcher has addressed potential impacts to pygmy rabbits due
to climate change. In California and Nevada, Larrucea and Brussard
(2008b, p. 1640) found extant historical pygmy rabbit sites averaged
515 ft (157 m) higher than extirpated sites. With local downward shift
effect accounted for, overall upward elevation shift of extant sites
was 721.8 ft (220 m); the researchers attributed this to climate. Over
the last century, a 0.7 degree Celsius temperature increase has
occurred, which correlates with a predicted elevational shift upwards
of 383.9 ft (117 m) (Peters 1989, cited in Larrucea and Brussard 2008b,
p. 1640). Warmer temperatures are also expected to increase fire
intensity and frequencies (Westerling et al. 2006, cited in Larrucea
2007, pp. 63-64). Warming temperatures may continue to shift upward the
lower elevational boundary of habitable pygmy rabbit sites.
The prehistoric record for pygmy rabbits in the Great Basin
indicates a wider distribution than today and declines have occurred
since the end of the Pleistocene (Kurten and Anderson 1972, p. 21;
Findley et al., 1975, Gillespie 1984, Harris 1985, 1993a cited in
Grayson 2006 pp. 2969-2970). The beginning of the middle Holocene in
the Great Basin also saw a decline in pygmy rabbit abundance (Grayson
2006, pp. 2971-2972). The decline is attributed to this period
experiencing elevated temperatures and decreased precipitation in the
Great Basin (Grayson 2006, p. 2972). A third decline in pygmy rabbit
abundance in the Great Basin is associated with the development of
pinyon-juniper woodland within the region (Grayson 2006, pp. 2973-
2974). Establishment of pinyon-juniper in this area and its associated
decline in pygmy rabbit numbers is best explained by the loss of
sagebrush-grass habitat (Grayson 2006, p. 2974). Pygmy rabbits occur in
the prehistoric record in New Mexico (Grayson 2006, p. 2970), but they
are not currently known to occur in the State, though sagebrush habitat
does exist there. The habitat may have changed to such an extent since
prehistoric times that it no longer provides appropriate habitat for
pygmy rabbits. Butler (1972, p. 52) stated that the population of pygmy
rabbits on the Eastern Snake River Plain was greater prior to 7,000
years ago. The decline in abundance of pygmy rabbits and pocket gophers
(common in grassy meadows) at the beginning of the 7\th\ millennium
B.P. and accompanied by a proportional increase in the pygmy rabbit may
indicate a change in climate that had more impact on grasses and forbs
than on sagebrush (Butler 1972, p. 52).
A warming trend in the mountains of western North America is
expected to decrease snow pack, accelerate spring runoff, and reduce
summer flows (Intergovernmental Panel on Climate Change (IPCC) 2007, p.
11). Increased summer temperatures may increase the frequency and
intensity of wildfires (IPCC 2007, p. 13). Recent warming is linked, in
terrestrial ecosystems, to pole-ward and upward shifts in plant and
animal ranges (IPCC 2007, p. 2). Climate projections predict the Great
Basin region is likely to become warmer and drier (Peters and Lovejoy
1992, cited in Larrucea 2007, p. 63).
It is difficult to predict local climate change impacts due to
substantial uncertainty in trends of hydrological variables,
limitations in spatial and temporal coverage of monitoring networks,
and differences in the spatial scales of global climate models and
hydrological models (Bates et al. 2008, p. 3). Climate change models
that are currently available are not yet capable of making meaningful
predictions of climate change for specific, local areas (Parmesan and
Matthews 2005, p. 354). Thus, while the best available information
indicates that climate change has the potential to affect habitats used
by pygmy rabbits in the Great Basin in the long-term, there is much
uncertainty regarding which habitat attributes (including sagebrush,
grass, and forbs communities) could be affected, and the timing,
magnitude, and rate of their change as it relates to pygmy rabbits and
their needs.
Summary of Climatic Change Impacts
Extant historical populations may indicate an upward shift in
elevation due to climatic changes or this shift may be due to other
unknown factors. The prehistoric record shows the range of the pygmy
rabbit occurred over a larger area than today, and the range
contraction has been attributed, in part, to increased temperatures and
decreased precipitation. It is reasonable to assume that pygmy rabbits
of today may be likewise affected in the Great Basin due to possible
warmer and drier conditions. Climate change could also facilitate the
establishment of invasive plant species or exacerbate the fire regime.
Pinyon and juniper woodland expansion may increase, however this may be
a slow process and may result in less sagebrush habitat being available
for the pygmy rabbit in the future. However, while there is some
evidence to suggest there may be an upward shift in elevation or
contracted range due to climatic changes, we have no information to
suggest that climate change will significantly affect the pygmy rabbit.
Based on our review of the available information, there is no
demonstrated direct link between predicted climate change and reduced
abundance and survival of pygmy rabbits. The best scientific and
commercial information currently available does not indicate that
climate change is a significant threat to the species now or in the
foreseeable future.
Recreational Activities
Recreational activities, especially off-highway vehicle/off-road
vehicle (OHV/ORV) and snowmobile use, have the potential to be a threat
to pygmy rabbits and their sagebrush habitat by disturbing individuals
through excessive noise, damaging sagebrush, or damaging burrows or
subnivian tunnels. Additionally, recreation could increase the spread
of weeds, and human presence and pets in a particular area. Much of the
sagebrush habitat across the range of the pygmy rabbit is open to
recreational use. Based on our review of the best available
information, we found one document that indicates pygmy rabbits occupy
an area used by OHV/ORV users in Oregon (BLM 2008d, p. 6). In addition,
in Idaho, Bradfield (1974, pp. 35-36) suggested that the pygmy rabbit
depends on its hearing for predator detection and may be less active
during windy periods when predator detection may be reduced. This study
may suggest noise from a passing vehicle could make pygmy rabbits more
vulnerable to predation.
Summary of Recreational Activities Impacts
Recreational activities occur in sagebrush habitat within the range
of the pygmy rabbit, however, our review of the best scientific and
commercial information available identified only one instance of
recreational activities or areas where these activities may be directly
or indirectly impacting pygmy rabbits. This area continued to support a
number of active pygmy rabbit burrows. Therefore, we conclude that the
best scientific and commercial information available does not indicate
that recreational activities are a
[[Page 60557]]
significant threat to the pygmy rabbit now or in the foreseeable
future.
Vehicle Collisions
Roads are known to exist throughout the range of the pygmy rabbit.
Jones (1957, p. 274) mentions a pygmy rabbit winter road kill in
California north of Crowley Lake, Mono County, and in Wyoming a study
mentions a previously reported road kill near Pinedale (Purcell 2006,
p. 8). Bradfield (1974, p. 3) suggested that pygmy rabbits were
reluctant to cross open areas based on the lack of observed highway
mortality (Gordon 1932, Sperry 1933, Smith 1943, cited in Bradfield
1974, p. 3). We are not aware of any documentation of pygmy rabbit
mortalities due to snowmobiles or OHVs and ORVs. Additionally, there is
no indication that vehicle mortalities have increased, or will increase
in the future, as the density of roads have increased across the range
of the species.
Summary of Vehicle Collisions Impacts
While we are aware of reports of road mortalities in Wyoming and
California related to pygmy rabbits, they are few in number with low
mortalities documented. We conclude that populations are able to
recover from these types of limited, individual losses. Based on our
review of the best available information, we conclude that mortality
due to vehicular collisions is not a significant threat to the pygmy
rabbit now or in the foreseeable future.
Habitat Specialist
Because the pygmy rabbit is a habitat specialist and its habitat is
fragmented across the landscape, the species' life history traits could
affect population viability. Pygmy rabbits appear to have small home
ranges, are not evenly distributed across the species' range, and may
have poor dispersal capabilities (though recent information indicates
home ranges and dispersal capabilities are greater than originally
thought) influencing genetic diversity or its ability to move to a more
favorable location if necessary in reaction to natural or manmade
factors. Pygmy rabbits do not respond to abundant spring food supply by
producing additional litters like other rabbits and therefore, may have
lower reproductive capabilities (Wilde 1978, p. 145). These life
history traits could contribute to population declines as habitat size
and quality are reduced, however, they should not be a limiting factor
to pygmy rabbits across large geographic areas when suitable habitat is
extensive and in good condition.
Summary of Habitat Specialist Impacts
The pygmy rabbit is a habitat specialist. Life history traits such
as small home ranges, uneven distribution across its range, poor
dispersal capabilities and lower reproductive potential compared to
other leporid species might suggest a concern for the long-term
survival of the pygmy rabbit. However, recent studies as mentioned in
the Background section above indicate that pygmy rabbit home ranges and
dispersal capabilities are greater than previously thought. Genetic
research (Estes-Zumpf et al. 2010, p. 214) has occurred in some areas
of the species' range, and available information indicates the pygmy
rabbit exhibits relatively high genetic diversity. The best available
scientific and commercial information does not indicate that the pygmy
rabbit is negatively impacted by current habitat fragmentation. The
information available indicates pygmy rabbit populations continue to
occur over a wide distribution of their current range.
The pygmy rabbit survives almost exclusively on sagebrush for food
(especially in winter) and shelter. Sagebrush are long-lived, stable
species, resistant to most environmental impacts, except fire and some
insects, and thus do not fluctuate widely in availability. The best
available information does not indicate how the lack of producing
additional litters specifically during times of abundant plant growth
is detrimental to the species. However, as indicated in the background
section, female pygmy rabbits are capable of producing an average of
six young per litter with three litters possible in a year. The best
available information shows that the pygmy rabbit's natural life
history characteristics have not limited the species across its range.
Therefore, we conclude that being a habitat specialist is not a
significant threat to the pygmy rabbit now or in the foreseeable
future.
Other Potential Threats
In our 90-day petition finding, we identified other natural or
manmade factors (facilities associated with grazing (tanks, pipelines,
roads) may allow predators, OHV/ORV users, and hunters to access new
terrain; activities on military facilities; and predator control to
benefit livestock increases predation on pygmy rabbits) that might pose
a threat to pygmy rabbits. However, for this analysis, we could find no
supporting information to indicate that any of these factors are
threatening pygmy rabbit populations.
Summary of Factor E
We have assessed the best available scientific and commercial data
on the magnitude and extent of the potential threats of intra- and
inter-specific relationships, small or isolated populations, stochastic
events, climate change, recreational activities, vehicle collisions,
and habitat specialist life history requirements of the pygmy rabbit.
As discussed above, intra- and inter-specific relationships between and
among pygmy rabbits and other species are natural and occur but do not
constitute a significant threat to the species. The best available
scientific and commercial information does not document that natural or
anthropogenic pressures are negatively affecting these relationships.
The best available information indicates that pygmy rabbit populations
are not small or occurring in isolation across the range. While
stochastic events have occurred and will continue to occur throughout
the range of the species, there is no indication that these events are
a significant threat to the pygmy rabbit largely due to the patchy
distribution of the species and its preferred habitat. Vehicle
collisions, while a potential threat, have been rarely reported, and we
do not consider them to be a significant source of mortality. Projected
climate change impacts across the range of the pygmy rabbit are
generalized and are not considered to be a significant threat. The
potential impact of pinyon-juniper woodland expansion into pygmy rabbit
habitat is predicted to be slow with pygmy rabbits demonstrating a
variety of responses. Recreational activities occur within the range of
the pygmy rabbit, but no information is available to qualify or
quantify the effect on populations, and we do not considered these
activities to be a significant threat. There is no indication from the
available information that the pygmy rabbit has been limited across its
range based on its natural life history characteristics. There are many
natural and manmade factors or activities that have occurred and will
continue to occur within pygmy rabbit habitats within its range. As
discussed in the distribution and trend section, the available
information indicates pygmy rabbit populations continue to occur over a
wide distribution of their current range, including historical
locations, despite these various factors. Based on the best available
scientific and commercial information, the pygmy rabbit is not now, or
in the foreseeable future, threatened by other natural or manmade
factors affecting the species to the extent that listing as endangered
or
[[Page 60558]]
threatened under the Act is warranted at this time.
Finding
As required by the Act, we considered the five factors in assessing
whether the pygmy rabbit is endangered or threatened throughout all or
a significant portion of its range. We carefully examined the best
scientific and commercial information available regarding the past,
present, and future threats faced by the pygmy rabbit. We reviewed the
petition, information available in our files, other available published
and unpublished information, and we consulted with recognized pygmy
rabbit experts and other Federal, State, and tribal agencies.
We have identified and evaluated the potential threats as discussed
under Factor A (agriculture, sagebrush treatment, livestock grazing,
nonnative invasive plants, fire, urban and rural development, mining,
energy exploration and development, habitat fragmentation, and greater
sage-grouse conservation actions), and we acknowledge that most of
these threats have occurred within the range of the pygmy rabbit and
may have impacted some areas known to be, or to have been, occupied by
pygmy rabbits based on site-specific information. Some or all of these
activities are likely to continue at some level in the future.
Available information does not indicate that the sagebrush lost or
degraded due to agriculture, sagebrush treatment, urban and rural
development, mining, habitat fragmentation, greater sage-grouse
conservation actions, or other conservation actions has impacted large
areas of suitable or occupied pygmy rabbit habitat resulting in
significant occupied habitat or population losses. The impacts
attributed to livestock grazing, while widespread across the pygmy
rabbit's range, have not resulted in documented measurable declines in
pygmy rabbit numbers or populations. Based on the information
available, we find that the potential threat of increasing energy
exploration and development as well as the relationship between
invasive nonnative plant species and fire regimes are not significant
threats to the pygmy rabbit now or in the foreseeable future. There is
no available information that indicates the magnitude or extent of
pygmy rabbit sites that may have been lost or reduced in area or in
population size due to these activities. Some of these events or
actions that can result in the complete loss of sagebrush over large
areas (i.e., sagebrush conversion to agriculture, sagebrush treatments,
fire) likely resulted in the reduction of occupied habitat and loss of
some pygmy rabbit populations. However, there is no evidence that this
will significantly threaten the species in the foreseeable future.
Therefore, based on our review of the best available scientific
information, we find these potential threats, either singly or in
combination with one another, are not significant threats now or in the
foreseeable future, to pygmy rabbit habitat across its range.
We have identified and evaluated the risks from overutilization for
commercial, recreational, scientific or educational purposes. Available
information indicates that historical or recent hunting pressure has
not played an important role in population dynamics for the pygmy
rabbit across its range. Three of the seven States discussed in this
finding currently allow hunting of pygmy rabbits; this is a reduction
from the past. Based on the best available information we find that
hunting was not and is not a significant threat to pygmy rabbit
populations across its range nor will it be in the foreseeable future.
Research activities may result in adverse impacts to a species
(e.g., injury, death, stress, or general habitat disturbance). Negative
impacts to pygmy rabbits that have been caused by research activities
have been few in number, occurred in limited areas, and occurred over
short periods of time. We encourage research activities to continue in
the future to increase our understanding of this species. With planning
and care, adverse impacts of research activities can be minimized.
Based on the best available information we find that research
activities are not a significant threat now or in the foreseeable
future, to the pygmy rabbit across its range.
Disease epizootics in pygmy rabbits have not been reported within
its range considered in this finding. Research is needed to determine
if disease could be a threat in the future. Predation has been reported
as the main cause of mortality in pygmy rabbits. Numerous species have
been identified as predators of pygmy rabbits. Based on the best
available information, we find that neither disease nor predation are
significant threats now or in the foreseeable future, to the pygmy
rabbit across its range.
Based on our analysis of the existing regulatory mechanisms, we
determined that States are managing pygmy rabbit hunting in three
States while four others protect them hunting as species of concern or
sensitive species. In Wyoming, many oil and gas projects will be
reviewed and mitigation provided that may benefit pygmy rabbits.
A large portion of pygmy rabbit habitat occurs on lands
administered by Federal agencies and numerous policies, guidance, and
laws have been developed to assist in managing these lands. We
determined in the evaluation that other threats would not significantly
affect the pygmy rabbit now or in the foreseeable future. Thus, we find
the inadequacy of existing regulatory mechanisms is not a significant
threat to the pygmy rabbit across its range now or in the foreseeable
future.
Other natural or manmade factors have occurred within the range of
the pygmy rabbit, and these habitat impacts or actions will likely
continue at some level in the future. As indicated above, intra- and
inter-specific relationships between pygmy rabbits and among pygmy
rabbits and other species are natural and occur across the range, but
there is no indication that these relationships are negatively
impacting the pygmy rabbit. Though impacts to pygmy rabbits have
occurred related to stochastic events and vehicle collisions, they have
been rarely reported. The best available information indicates that
pygmy rabbit populations are not small or isolated across the range.
Potential impacts due to climate change are general, and there is no
demonstrated connection between climate change and reduced abundance or
survival of pygmy rabbits. Recreational activities occur throughout the
range of the pygmy rabbit, but there is no indication these activities
are significantly impacting pygmy rabbit populations. The best
available information indicates that the pygmy rabbit, as a habitat
specialist, has not been limited across its range.
During our status review for this species, it has become evident
that many of the threat issues raised have been speculative and direct
impacts to historical and extant pygmy rabbit populations have not been
documented. Threats exist but do not appear to be significant across
the range of the species. While the sagebrush ecosystem has been and
will continue to be impacted by various natural and manmade events and
activities in parts of the pygmy rabbit's range, we have determined,
based on the species' current range and distribution, that pygmy rabbit
populations continue to persist in much of its range, despite the
numerous activities occurring within their habitat. Pygmy rabbits are
represented across their current range which is not dissimilar from
what is known of their historical distribution as
[[Page 60559]]
discussed in the Distribution and Trend section. Our understanding of
the pygmy rabbit's range has improved, and the current known range has
been extended in Montana, Nevada, and most notably Wyoming based on
recent survey efforts.
Based on our review of the best available scientific and commercial
information, we find that the threats are not of sufficient imminence,
intensity, or magnitude to indicate that the pygmy rabbit is in danger
of extinction (endangered), or likely to become endangered within the
foreseeable future (threatened) throughout its range. Therefore,
listing the pygmy rabbit as an endangered or threatened species under
the Act is not warranted at this time.
Distinct Vertebrate Population Segment (DPS)
After assessing whether the species is endangered or threatened
throughout its range, we next consider whether any distinct vertebrate
populations segment (DPS) exists and meets the definition of endangered
or is likely to become endangered in the foreseeable future
(threatened).
Under the Service's Policy Regarding the Recognition of Distinct
Vertebrate Population Segments Under the Endangered Species Act (61 FR
4722, February 7, 1996), three elements are considered in the decision
concerning the establishment and classification of a possible DPS.
These are applied similarly for additions to or removal from the
Federal List of Endangered and Threatened Wildlife. These elements
include:
(1) The discreteness of a population in relation to the remainder
of the taxon to which it belongs;
(2) The significance of the population segment to the taxon to
which it belongs; and
(3) The population segment's conservation status in relation to the
Act's standards for listing, delisting (removal from the list), or
reclassification (i.e., is the population segment endangered or
threatened).
In this analysis, we will evaluate whether pygmy rabbits in Mono
County, California, meet the criteria to be considered a DPS. This
analysis is being conducted because studies have indicated that pygmy
rabbit populations in Mono County may be separated from the rest of the
pygmy rabbit range (Grayson 2006, pp. 2969-2970; Larrucea and Brussard
2008a, pp. 694, 696).
Discreteness
Under the DPS policy, a population segment of a vertebrate taxon
may be considered discrete if it satisfies either one of the following
conditions:
(1) It is markedly separated from other populations of the same
taxon as a consequence of physical, physiological, ecological, or
behavioral factors. Quantitative measures of genetic or morphological
discontinuity may provide evidence of this separation.
(2) It is delimited by international governmental boundaries within
which differences in control of exploitation, management of habitat,
conservation status, or regulatory mechanisms exist that are
significant in light of section 4(a)(1)(D) of the Act.
We note that the standard set forth in the DPS policy is that a DPS
be ``markedly separated'' from other populations--thus, while absolute
separation is not required, neither are ``large numbers'' of
individuals migrating between populations. Nor is absolute isolation
required for populations to be markedly separated.
Pygmy rabbits in Mono County appear to be markedly separated from
other pygmy rabbit populations. The nearest known populations to Mono
County populations are in western Nevada, approximately 100 mi (162 km)
away (Larrucea and Brussard 2008a, p. 694). There are no known
historical pygmy rabbit records for Lyon, Mineral, and Emeralda
Counties, Nevada, which could provide possible connections between
California and Nevada in this area. Surveys conducted during 2003 and
2006 in Lyon and Mineral Counties did not find evidence of pygmy
rabbits (Larrucea 2007, pp. 165-179). It is possible that the Mono
County populations have been separated from the rest of the species'
range since the end of the Pleistocene (Grayson 2006, pp. 2969-2970).
We determine, based on a review of the best available information,
that the Mono County populations of pygmy rabbit are markedly separated
from other pygmy rabbit populations as a consequence of physical
factors and thus meet the discreteness criterion of the 1996 DPS
policy.
There are no international governmental boundaries associated with
this species that are significant. The pygmy rabbit is found wholly
within the United States. Because this element is not relevant in this
case for a finding of discreteness, it was not considered in reaching
this determination.
Significance
If a population segment is considered discrete under one or more of
the conditions described in our DPS policy, its biological and
ecological significance will be considered in light of Congressional
guidance that the authority to list DPSs be used ``sparingly'' while
encouraging the conservation of genetic diversity. In making this
determination, we consider available scientific evidence of the
discrete populations segment's importance to the taxon to which it
belongs. Since precise circumstances are likely to vary considerably
from case to case, the DPS policy does not describe all the classes of
information that might be used in determining the biological and
ecological importance of a discrete population. However, the DPS policy
does provide four possible reasons why a discrete population may be
significant. As specified in the DPS policy (61 FR 4722), this
consideration of the population segment's significance may include, but
is not limited to, the following:
(1) Persistence of the discrete population segment in an ecological
setting unusual or unique to the taxon;
(2) Evidence that loss of the discrete population segment would
result in a significant gap in the range of a taxon;
(3) Evidence that the discrete population segment represents the
only surviving natural occurrence of a taxon that may be more abundant
elsewhere as an introduced population outside its historic range; or
(4) Evidence that the discrete population segment differs markedly
from other populations of the species in its genetic characteristics.
A population segment needs to satisfy only one of these criteria to
be considered significant. Furthermore, the list of criteria is not
exhaustive; other criteria may be used as appropriate.
(1) Persistence of the discrete population segment in an ecological
setting unusual or unique to the taxon;
The available information does not suggest that the ecological
setting occupied by pygmy rabbits in the Mono County, California,
portion of its range is unusual or unique when compared to the
remainder of its range. The available information does not suggest that
the vegetation, elevation, topography, or climate of the habitat
occupied by the Mono County, California populations of the pygmy rabbit
is unusual or unique to the taxon; nor is there any information
indicating there are physiological or behavioral factors of the Mono
County populations that are unusual or unique to the taxon.
[[Page 60560]]
(2) Evidence that loss of the discrete population segment would result
in a significant gap in the range of a taxon;
The Mono County populations are located on the western periphery of
the pygmy rabbit's range. We have determined that they occupy less than
1 percent of the species' range. If the populations in Mono County were
to be extirpated, the portion of the range lost would be small when
compared to the remainder of the species' range. Loss of these
populations would not result in a gap in the pygmy rabbit's range as
they are located on the edge of the range and may not be providing
connectivity to other portions of its range. Therefore, we conclude
that loss of these populations would not be result in a significant gap
in the range of the species.
(3) Evidence that the discrete population segment represents the
only surviving natural occurrence of a taxon that may be more abundant
elsewhere as an introduced population outside its historic range; or
The Mono County populations do not represent the only surviving
natural occurrence of a taxon that may be more abundant elsewhere as an
introduced population outside its historic range. The pygmy rabbit's
current distribution is similar to its historic distribution, and the
species has not been introduced to areas outside of its historic range.
The Mono county populations represent a small portion of the total
extent of the species' range.
(4) Evidence that the discrete population segment differs markedly from
other populations of the species in its genetic characteristics.
As indicated above, pygmy rabbits in Mono County have not been
genetically tested. Therefore, there is no information to indicate that
these populations differ markedly from other populations of this
species in its genetic characteristics.
We therefore conclude that pygmy rabbit populations in Mono County
do not meet the significance element of the Service's DPS policy
because they do not occur in an ecological setting unusual or unique to
the taxon; their loss would not result in a significant gap in the
range of the taxon; they do not represent the only surviving natural
occurrence of the taxon; and there is no evidence available indicating
that Mono County populations differ markedly in genetic
characteristics.
Conclusion of Distinct Population Segment Review
Based on the best scientific and commercial information available,
we find that pygmy rabbit populations found in Mono County, California,
meet the discreteness element of our DPS policy but fail to meet the
significance element of that policy. Since both discreteness and
significance are required to satisfy the DPS policy, we have determined
that Mono County pygmy rabbit populations do not qualify as a DPS under
our policy. As a result, no further analysis under the DPS policy is
necessary.
Significant Portion of the Range Analysis
Having determined that the pygmy rabbit is not endangered or
threatened throughout all its range, we must next consider whether
there are any significant portions of the range where the pygmy rabbit
is in danger of extinction or is likely to become endangered in the
foreseeable future.
To identify those portions that may be significant portions of the
range, we determine whether there is substantial information indicating
that: (i) The portions may be significant, and (ii) the species may be
in danger of extinction there or likely to become so within the
foreseeable future. In practice, a key part of this analysis is whether
the threats are geographically concentrated in some way. If the threats
to the species are essentially uniform throughout its range, no portion
is likely to be a significant portion of the range. Moreover, if any
concentration of threats applies only to portions of the range that are
unimportant to the conservation of the species, such portions will not
be significant portions of the range.
If we identify any significant portions, we then determine whether
the species is threatened or endangered in that portion of the range.
Depending on the biology of the species, its range, and the threats it
faces, the Service may address either the significance question or the
status question first. Thus, if the Service considers significance
first and determines that a portion of the range is not significant,
the Service need not determine whether the species is threatened or
endangered there. Likewise, if the Service considers status first and
determines that the species is not threatened or endangered in a
portion of its range, the Service need not determine if that portion is
significant.
Based on our review of survey information, distributional data, and
potential threats, we have determined that the pygmy rabbit range in
Oregon, Idaho, Montana, Nevada, and Utah does not warrant further
consideration to determine if it is a significant portion of the range
that is threatened or endangered. We found no areas within this portion
of the range where threats are geographically concentrated. The
potential factors that may affect the species are essentially uniform
throughout this portion of the range. However, we did determine that
the Mono County, California, and the Wyoming portions of the pygmy
rabbit's range warranted further consideration to determine if they are
significant portions of the range that are threatened or endangered.
The Mono County, California portion was selected due to the possible
lack of connectivity to populations in Nevada, and therefore, threats
to it may include population isolation. Regardless of the possible
extirpation of pygmy rabbit populations in Modoc and Lassen Counties,
California (Larrucea and Brussard 2008a, pp. 694, 696), populations in
Mono County may be isolated from the rest of the range. There are no
known historical pygmy rabbit records for Lyon, Mineral, and Emeralda
Counties, Nevada, which could provide possible connections between
California and Nevada in this area. Surveys conducted during 2003 and
2006 in Lyon and Mineral Counties did not find evidence of pygmy
rabbits (Larrucea 2007, pp. 165-179). It is possible that the Mono
County populations have been separated from the rest of the range since
the end of the Pleistocene (Grayson 2006, pp. 2969-2970) (see our
discussion regarding DPS above). The Wyoming portion was selected due
to the concentration of energy exploration and development in the
southwestern and south central areas of the State and the possible
threat from these activities to pygmy rabbit populations in those
areas.
To assess the significance of these portions of the range, we
evaluated whether these two areas occupy relatively large or
particularly high-quality, unique habitat that could be affected, or if
their locations or characteristics make them less susceptible to
certain threats than other portions of the species' range such that
they could provide important population refugia in the event of
extirpations elsewhere in the species' range. We determined that the
Mono County populations occupy less than 1 percent of the species
range, and the available information does not suggest that the habitat
occupied by pygmy rabbits in this portion is particularly high quality
or unique when compared to the remainder of the range. The pygmy
rabbit, in addition to Mono County California, occurs in sagebrush
habitats located in southeastern Oregon, southern Idaho, southwestern
Montana,
[[Page 60561]]
western Utah, and northern and eastern Nevada. We did not find that the
Mono County populations are less susceptible to certain threats than
other portions of the range. We also evaluated the historical value of
this portion and how frequently it is used by the species and whether
the portion contains important concentrations of certain types of
habitat that are necessary for the species to carry out its life-
history functions, such as breeding, feeding, migration, dispersal, or
wintering. We found that the Mono County populations are not
significant because the habitats necessary for breeding, feeding,
dispersal, or wintering are utilized year round and are found
throughout the pygmy rabbit's range. These necessary habitats are not
concentrated in Mono County.
We determined that the Wyoming populations occupy about 11.5
percent of the species' range, and available information does not
suggest that the habitat occupied by pygmy rabbits in this portion is
particularly high quality or unique when compared to the remainder of
the range. The pygmy rabbit, in addition to Wyoming, occurs in
sagebrush habitats located in southeastern Oregon, southern Idaho,
southwestern Montana, western Utah, and northern and eastern Nevada. We
did not find that the Wyoming populations are less susceptible to
certain threats than other portions of the range. We also evaluated the
historical value of this portion of the range and how frequently it is
used by the species and whether the portion contains important
concentrations of certain types of habitat that are necessary for the
species to carry out its life-history functions, such as breeding,
feeding, migration, dispersal, or wintering. We found that the Wyoming
populations are not significant because the habitats necessary for
breeding, feeding, dispersal, or wintering are utilized year round and
are found throughout the pygmy rabbit's range. These necessary habitats
are not concentrated in Wyoming.
Based on the discussion above, we determined that the Mono County,
California, and the Wyoming portions of the current range of the pygmy
rabbit are not significant to the species and therefore do not warrant
further consideration to determine if they are a significant portion of
the range that is threatened or endangered.
We do not find that the pygmy rabbit is in danger of extinction
now, nor is it likely to become endangered within the foreseeable
future throughout all or a significant portion of its range. Therefore,
listing the pygmy rabbit as threatened or endangered under the Act is
not warranted throughout all or a significant portion of its range at
this time.
We request that you submit any new information concerning the
status of, or threats to, the pygmy rabbit to our Nevada Fish and
Wildlife Office (see ADDRESSES section) whenever it becomes available.
New information will help us monitor the pygmy rabbit and encourage its
conservation. If an emergency situation develops for the pygmy rabbit,
we will act to provide immediate protection.
References Cited
A complete list of references cited is available on the Internet at
http://www.regulations.gov and upon request from the Nevada Fish and
Wildlife Office (see ADDRESSES).
Authors
The primary authors of this document are the staff members of the
Nevada Fish and Wildlife Office, U.S. Fish and Wildlife Service, Reno,
Nevada.
Authority
The authority for this action is section 4 of the Endangered
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).
Dated: September 20, 2010
Rowan Gould,
Acting Director, Fish and Wildlife Service.
[FR Doc. 2010-24349 Filed 9-29-10; 8:45 am]
BILLING CODE 4310-55-S