[Federal Register: August 28, 2009 (Volume 74, Number 166)]
[Proposed Rules]
[Page 44335-44344]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr28au09-22]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R2-ES-2009-0032]
[92210-1117-0000-B4]
Endangered and Threatened Wildlife and Plants; 90-Day Finding on
a Petition To List the Sonoran Population of Desert Tortoise (Gopherus
agasizzii) as a Distinct Population Segment (DPS) With Critical Habitat
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of petition finding and initiation of status review.
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SUMMARY: We, the U.S. Fish and Wildlife Service, announce a 90-day
finding on a petition to list the Sonoran desert tortoise (Gopherus
agasizzii) as a distinct population segment (DPS) under the Endangered
Species Act of 1973, as amended, and designate critical habitat. On the
basis of our review of the petition and information readily available
in our files, we have determined that there is substantial information
indicating that the Sonoran
[[Page 44336]]
desert tortoise may meet the criteria of discreteness and significance
as defined by our policy on distinct vertebrate population segments.
Further, we find that the petition presents substantial scientific or
commercial information indicating that listing the Sonoran population
of the desert tortoise may be warranted. Therefore, with the
publication of this notice, we are initiating a status review of the
Sonoran population of the desert tortoise to determine if listing the
population is warranted. To ensure that the status review of the
Sonoran population of the desert tortoise is comprehensive, we are
soliciting scientific and commercial data and other information
regarding this population. At the conclusion of this review, we will
issue a 12-month finding to determine if the petitioned action is
warranted. We will make a determination on critical habitat for the
Sonoran population of the desert tortoise if we initiate a listing
action.
DATES: We made the finding announced in this document on August 28,
2009. To allow us adequate time to conduct this review, we request that
we receive information on or before October 27, 2009.
ADDRESSES: You may submit information by one of the following methods:
Federal eRulemaking Portal: http://
www.regulations.gov. Follow the instructions for submitting comments.
U.S. mail or hand-delivery: Public Comments Processing,
Attn: [FWS-R2-ES-2009-0032]; Division of Policy and Directives
Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax Drive,
Suite 222; Arlington, VA 22203.
We will post all information received on http://
www.regulations.gov. This generally means that we will post any
personal information you provide us (see the Information Solicited
section below for more details).
FOR FURTHER INFORMATION CONTACT: Steve Spangle, Field Supervisor,
Arizona Ecological Services Office, 2321 West Royal Palm Drive, Suite
103, Phoenix, AZ 85021; by telephone 602-242-0210; or by facsimile 602-
242-2513. Persons who use a telecommunications device for the deaf
(TDD), may call the Federal Information Relay Service (FIRS) at 800-
877-8339.
SUPPLEMENTARY INFORMATION:
Information Solicited
When we make a finding that a petition presents substantial
information indicating that listing a species may be warranted, we are
required to promptly commence a review of the status of the species. To
ensure that the status review is complete and based on the best
available scientific and commercial information, we are soliciting
information on the status of the Sonoran population of the desert
tortoise (Sonoran desert tortoise). We request information from the
public, other concerned governmental agencies, Native American Tribes,
the scientific community, industry, or any other interested parties
concerning the status of the Sonoran desert tortoise. We are seeking
information regarding:
(1) The historical and current status and distribution of the
Sonoran desert tortoise (particularly with respect to Mexico), its
biology and ecology, and ongoing conservation measures for the species
and its habitat;
(2) Information relating the importance of the Sonoran desert
tortoise population to the species as a whole;
(3) Information relevant to the factors that are the basis for
making a listing determination for a species under section 4(a) of the
Endangered Species Act of 1973, as amended (Act) (16 U.S.C. 1531 et
seq.), which are:
(a) the present or threatened destruction, modification, or
curtailment of the species' 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 and threats to the species or its habitat; and
(4) Information about any ongoing conservation measures for, or
threats to, the Sonoran desert tortoise and its habitat.
If we determine that listing the Sonoran desert tortoise is
warranted, it is our intent to propose critical habitat to the maximum
extent prudent and determinable at the time we would propose to list
the Sonoran desert tortoise. Therefore, with regard to areas within the
geographical range currently occupied by the Sonoran desert tortoise,
we also request data and information on what may constitute physical or
biological features essential to the conservation of the Sonoran desert
tortoise, where these features are currently found, and whether any of
these features may require special management considerations or
protection. In addition, we request data and information regarding
whether there are areas outside the geographical area occupied by the
Sonoran desert tortoise that are essential to its conservation. Please
provide specific comments and information as to what, if any, critical
habitat should be proposed for designation if the Sonoran desert
tortoise is proposed for listing, and why such habitat meets the
requirements of the Act.
Please note that comments merely stating support for or opposition
to the action under consideration without providing supporting
information, although noted, will not be considered in making a
determination, as section 4(b)(1)(A) of the Act directs that
determinations as to whether any species is a threatened or endangered
species must be made ``solely on the basis of the best scientific and
commercial data available.'' Based on the status review, we will issue
a 12-month finding on the petition, as provided in section 4(b)(3)(B)
of the Act.
You may submit your information concerning this finding by one of
the methods listed in the ADDRESSES section.
If you submit information via http://www.regulations.gov, your
entire submission--including any personal identifying information--will
be posted on the website. If your submission is made via a hardcopy
that includes personal identifying information, you may request at the
top of your document that we withhold this information from public
review. However, we cannot guarantee that we will be able to do so. We
will post all hardcopy submissions on http://www.regulations.gov.
Information and materials we receive, as well as supporting
documentation we used in preparing this finding, will be available for
public inspection on http://www.regulations.gov, or by appointment,
during normal business hours, at the U.S. Fish and Wildlife Service,
Arizona Ecological Services Office (see FOR FURTHER INFORMATION
CONTACT).
Background
Section 4(b)(3)(A) of the Act requires that we make a finding on
whether a petition to list, delist, or reclassify a species presents
substantial scientific or commercial information to indicate that the
petitioned action may be warranted. We are to base this finding on
information contained in the petition, supporting information submitted
with the petition, and information otherwise available in our files. To
the maximum extent practicable, we are to make this finding within 90
days of receipt of the petition and publish our notice of this finding
promptly in the Federal Register.
Our standard for substantial scientific or commercial information
within the
[[Page 44337]]
Code of Federal Regulations (CFR) with regard to a 90-day petition
finding is ``that amount of information that would lead a reasonable
person to believe that the measure proposed in the petition may be
warranted'' (50 CFR 424.14(b)). If we find that substantial scientific
or commercial information was presented, we are required to promptly
commence a status review of the species.
On October 15, 2008, we received a petition dated October 9, 2008,
from WildEarth Gardians and Western Watersheds Project (petitioners)
requesting that the Sonoran population of the desert tortoise be listed
under the Act as a distinct population segment (DPS), as threatened or
endangered rangewide (in the United States and Mexico), and critical
habitat be designated. The petition clearly identified itself as such
and included the requisite identification information for the
petitioners, as required in 50 CFR 424.14(a). The petition contained
detailed information on the natural history, biology, current status,
and distribution of the Sonoran population of the desert tortoise. It
also contained information on what the petitioners reported as
potential threats to the Sonoran population of the desert tortoise,
such as livestock grazing, urbanization and development, mining,
international border patrol activities, illegal collection, inadequacy
of existing regulations, altered fire regimes, off-highway vehicle use,
drought, and climate change. In a November 26, 2008, letter to the
petitioners, we responded that we had reviewed the information
presented in the petition and determined that issuing an emergency
regulation temporarily listing the species as per section 4(b)(7) of
the Act was not warranted. We also stated that we intended to make our
finding on whether the petition presented substantial information that
the requested action may be warranted, to the maximum extent
practicable within 90 days of receipt of the petition, according to the
provisions of section 4(b)(3) of the Act.
Previous Federal Actions
Throughout this finding, we use ``Mojave'' to describe desert
tortoise populations north and west of the Colorado River, which is
consistent with the previous and current spelling of the common name in
Federal actions that have addressed this population. We use ``Mohave''
in the geographic context to remain consistent with its reference by
the U.S. Board of Geographic Names (e.g., Mohave Desert, Mohave
County). In addition, while we do not currently recognize the Sonoran
population of the desert tortoise as a unique taxonomic entity, for
ease of reference, we refer to the Sonoran population of the desert
tortoise as the ``Sonoran desert tortoise'' in this document.
On December 30, 1982, we published a notice of review which
determined the desert tortoise throughout its range in the United
States and Mexico to be a Category 2 Federal Candidate species (47 FR
58454); this was reaffirmed on September 18, 1985 (50 FR 37958).
Category 2 status was granted to species for which information in our
possession indicated that a proposed listing as threatened or
endangered was possibly appropriate, but for which sufficient data were
not available to make a determination of listing status under the Act.
On April 2, 1990, we issued a final rule designating the Mojave
population of the desert tortoise (occurring north and west of the
Colorado River) as a threatened species under the Act (55 FR 12178; see
final rule for a summary of previous actions regarding the Mojave
population of the desert tortoise). Currently, the Mojave population of
the desert tortoise is recognized as a DPS under the Act. As part of
that rulemaking, we designated any desert tortoise from the Sonoran
population as threatened when observed outside of its known range, due
to similarity of appearance under section 4(a) of the Act.
On December 5, 1996, we published a rule that discontinued the
practice of keeping a list of category 2 candidate species (61 FR
64481). Since that time, the Sonoran desert tortoise has had no Federal
Endangered Species Act status.
Species Information
The desert tortoise is a member of the Testudinidae family
(terrestrial tortoises) of turtles in the genus Gopherus (Rafinesque
1832), or gopher tortoises. Scientific nomenclature assigned to the
desert tortoise has undergone a series of changes since its initial
description by Cooper (1863) as Xerobates agassizii. The desert
tortoise was also once known as Scaptochelys agassizii (Crother et al.
2008, p. 70). Further information is available on classification of the
desert tortoise in Van Devender (2002b), Lamb and McLuckie (2002), and
McCord (2002).
The desert tortoise is recognized by its gray to orange-brown,
high, domed upper shell. The shell measures 8 to 15 inches (20 to 38
centimeters) in length (Service 2008, p. 4). Adult desert tortoises may
weigh 8 to 15 pounds (3.6 to 6.8 kilograms) (Service 2008, p. 4). Hind
limbs of the desert tortoise are stocky and elephantine in appearance
while the forelimbs are paddle-shaped and used for digging (Brennan and
Holycross 2006, p. 54). In the wild, desert tortoises have an average
lifespan of 35 years (Germano 1994).
The Sonoran desert tortoise is closely associated with rocky
bajadas (lower slopes of mountains) and hillsides, and, to a lesser
extent, flat areas (including incised washes between or adjacent to
flat terrain) (Riedle et al. 2008). Sonoran desert tortoises generally
occur at elevations ranging from 510 to 5,300 feet (155 to 1,615
meters) (Arizona Game and Fish Department 2001, p. 4).
In the United States, the Sonoran desert tortoise occurs within
Mohave desertscrub, Sonoran desertscrub, and semi-desert grassland
habitat (Germano et al. 1994; Van Devender 2002a; Brennan and Holycross
2006, p. 54). In Mexico, the Sonoran desert tortoise occurs in Sonoran
desertscrub and semi-desert grassland (Germano et al. 1994; Fritts and
Jennings 1994; Bury et al. 2002; Van Devender 2002a; Edwards et al.
2009, p. 8). The Sonoran desert tortoise may also occasionally occur in
the lower elevations of Madrean oak woodland (Germano et al. 1994;
Fritts and Jennings 1994; Bury et al. 2002; Van Devender 2002a).
Primarily herbivores, Sonoran desert tortoises consume a variety of
plant material in their diet (Van Devender et al. 2002).
Sonoran desert tortoises are largely inactive from mid-October to
late February or early March when they overwinter in constructed
burrows or rocky cavities or crevices (Averill-Murray 2000b). Sonoran
desert tortoises tend to use or construct burrows differently,
depending on habitat. Riedle et al. (2008) found that the availability
of adequate shelter sites strongly influenced Sonoran desert tortoise
densities.
Tortoise activity spikes in the spring, especially following
average or above-average winter precipitation that enhances annual
plant production (Averill-Murray 2000b). However, the peak activity for
the Sonoran desert tortoises occurs at the onset of the monsoon (summer
rainy season) in mid- to late-summer when annual and perennial plants
reach peak abundance and availability, and water sources become more
widely dispersed across the landscape (Averill-Murray 2000b). During
the hot and dry late-spring/early-summer season, Sonoran desert
tortoises are less active or may become entirely dormant until the
onset of the monsoon (Averill-Murray 2000b).
The monsoon also marks the height of social interaction and
reproductive behaviors for the Sonoran desert tortoise. During this
time, female
[[Page 44338]]
Sonoran desert tortoises lay their eggs, with an average clutch size of
5 (Averill-Murray and Klug 2000). Hatchling Sonoran desert tortoises
will emerge from the nest site (burrow) in late summer or they may
overwinter, emerging the following spring (Wilson et al. 1999; Averill-
Murray 2000b). Sonoran desert tortoises reach sexual maturity at
approximately 10 to 12 years of age (Averill-Murray 2000b).
Desert tortoises are distributed from California, Nevada, Utah, and
Arizona in the United States, south through the Mexican states of
Sonora and Sinaloa. The specific distribution of desert tortoise is
likely determined by habitat and climatic characteristics (e.g.,
vegetation community (food), soil and substrate characteristics
(shelter), precipitation pattern (water availability)) within the
appropriate elevation range. The distribution of the Sonoran desert
tortoise in the United States is considered to be east and south of the
Colorado River, extending south and east from northwestern Mohave
County in Arizona (Germano et al. 1994; Van Devender 2002a, Brennan and
Holycross 2006, p. 54), covering roughly the western portion of the
state. The distribution in the United States is likely bounded to the
northeast and east by habitat changes imposed by the Mogollon Rim. In
Mexico, the distribution of the Sonoran desert tortoise extends from
the International Border of Sonora and Arizona, south to the vicinity
of Guaymas, north of the Yaqui River, in southern Sonora (Germano et
al. 1994; Fritts and Jennings 1994; Bury et al. 2002; Van Devender
2002a; Edwards et al. 2009, pp. 7-8), covering approximately the
western half of the state of Sonora from the Gulf of California coast
east roughly to the transition to unsuitable woodland and conifer
forest areas in the higher elevations of the Sierra Madre Occidental.
The Mojave and Sinaloan populations of desert tortoises represent two
additional populations of this species recognized in the literature
(Lamb and McLuckie 2002). The Mojave population, listed as threatened
in 1990, includes those populations that occur north and west of the
Colorado River in southern California, southern Nevada, southwestern
Utah, and extreme northwestern Arizona; and the Sinaloan population is
considered to be generally distributed along and within the western
face of the Sierra Madre Occidental of central Sonora south into the
border region between Sonora and Sinaloa at the extreme southern end of
the species' range (Lamb and McLuckie 2002). Genotypes (genetic makeup
of an organism) differ significantly between populations (Lamb and
McLuckie 2002).
Distinct Population Segment
Under section 3(15) of the Act, we may consider for listing any
species, subspecies, or, for vertebrates, any DPS of these taxa. In
determining whether an entity constitutes a DPS, and is therefore
listable under the Act, we follow the Policy Regarding the Recognition
of Distinct Vertebrate Population Segments Under the Endangered Species
Act (DPS Policy) (61 FR 4722; February 7, 1996). Under our DPS Policy,
three elements are considered in a decision regarding the status of a
possible DPS: (1) the discreteness of the population segment in
relation to the remainder of the taxon; (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 (i.e., whether the population segment, when
treated as if it were a species, is endangered or threatened) (61 FR
4722, February 7, 1996). The first two elements are used to determine
if the population segments constitutes a valid DPS. If it does, then
the third element is used to consider whether such DPS warrants
listing. In this section, we will consider the first two criteria
(discreteness and significance) to determine if the Sonoran desert
tortoise may be a valid DPS (i.e., a valid listable entity). Our policy
further recognizes it may be appropriate to assign different
classifications (i.e. threatened or endangered) to different DPSs of
the same vertebrate taxon (61 FR 4721).
The petitioners requested we examine the Sonoran desert tortoise as
a DPS. The information discussed below was presented by the
petitioners, unless otherwise noted.
The petitioned DPS includes those populations that occur east and
south of the Colorado River, south to the biogeographical boundary of
the Yaqui River in southern Sonora, Mexico. In making this delineation
for the petitioned DPS, the petitioners considered biogeographic
isolation, ecological divergence, morphological and physiological
characteristics, and genetic polymorphisms (genetic material occurring
in multiple forms or configurations).
The petitioners discuss a population of desert tortoise with the
``Mojave'' genotype (i.e., having similar genetic characteristics to
the those of the Mojave DPS of desert tortoise) which occurs in the
Black Mountains of Mohave County, Arizona (isolated from the threatened
Mojave DPS that occurs north and west of the Colorado River), and are
seeking the inclusion of that population within the petitioned DPS
because it does not currently have protection under the Act. We will
evaluate this anomalous situation further in our 12-month finding.
Discreteness
Under the DPS Policy, a population segment of a vertebrate species
may be considered discrete if it satisfies either one of the following
two 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; or
(2) it is delimited by international governmental boundaries within
which significant differences in control of exploitation, management of
habitat, conservation status, or regulatory mechanisms exist (61 FR
4722, February 7, 1996).
Information Provided in the Petition on Discreteness
The petitioners claim that the Sonoran population is discrete from
the Mojave and Sinaloan populations due to differences in habitat use,
reproduction strategies, physical characteristics, and genotype. The
petitioners claim that the Colorado (United States) and Yaqui (Sonora,
Mexico) Rivers act as biogeographical barriers to movement of tortoises
between the Mojave and Sonoran populations, and between the Sonoran and
Sinaloan populations, respectively. In view of this biogeographical
isolation, the petitioners claim that significant ecological divergence
has occurred between the Mojave and Sonoran populations of desert
tortoise, largely due to significant differences in geology, vegetation
types, and precipitation cycles where the populations are distributed.
Desert tortoises in the Mojave population are most dense in the
intermountain valleys that have soil types favorable to the
construction of large, deep burrows (Bury et al. 1994). However,
Sonoran desert tortoises reach maximum densities in the rocky bajadas
and hillsides of higher slope, with reduced densities in the
intermountain valleys (Averill-Murray et al. 2002b). The petitioners
state that differences in precipitation cycle have led to notable
differences in seasonal activity patterns between desert tortoises that
occur in the Sonoran and Mojave deserts. Information in our files
confirms these assertions. Specifically, analyzing the genetic
population structure among desert tortoise populations in Mexico,
[[Page 44339]]
Edwards et al. (2009, pp. 7-8) suggest the Sinaloan population of
desert tortoise uses Sinaloan thornscrub and tropical deciduous forest
habitats (which are created by higher precipitation levels). However,
some level of gradation of the Sonoran and Sinaloan genotypes may occur
in the vegetative transition zone between Plains of Sonora subdivision
of Sonoran desertscrub and Sinaloan thornscrub habitats of central
Sonora (Edwards et al. 2009, p. 8).
Differences in reproduction strategies between the Sonoran and
Mojave populations of desert tortoises were also discussed in the
petition. In the Mojave population of desert tortoises, females lay up
to three clutches of eggs per year with larger clutch sizes, earlier in
the year (April to mid-July) while those in the Sonoran population lay
one clutch per year of smaller size, later in the year (June through
August) (Wallis et al. 1999; Averill-Murray et al. 2002a). These
differences led Averill-Murray (2002b) and Henen (1997) to hypothesize
that Sonoran desert tortoises invest all reproductive effort into a
single clutch which hatches at the peak of forage and water
availability and abundance, whereas desert tortoises in the Mojave
population (maturing at younger ages and at smaller body sizes), have
higher clutch numbers to account for higher mortality. Comparative
reproduction strategies of the Sinaloan population of the desert
tortoise were not discussed in the petition.
The petitioners claim morphological and physiological
characteristics, in particular, shell characteristics, differ between
the Sonoran and Mojave populations of desert tortoises. Germano (1993)
found that desert tortoise shells in the Sonoran population are
narrower than those in the Mojave population, were less domed, and
possessed shorter gular shields (plates projecting forward from the
lower shell). Desert tortoises in the Sonoran population also have a
smaller plastron (lower shell) and a broader carapace (upper shell)
(McLuckie et al. 1999). The petitioners did not provide information on
the potential differences in morphological and physiological characters
between the Sonoran and Sinaloan populations of desert tortoises.
Lastly, the petitioners rely on genetic polymorphisms (that is,
genetic material occurring in multiple forms) as a primary basis to
consider the Mojave, Sonoran, and Sinaloan populations of desert
tortoises as evolutionarily significant units. The Mojave population of
desert tortoise exhibits three related genotypes but the Sonoran desert
tortoise possesses a single genotype that is closely associated with
Arizona upland and lower Colorado River subdivisions of Sonoran
desertscrub habitat where the species is generally found (Lamb et al.
1989; Lamb and McLuckie 2002). Lamb and McLuckie (2002) suggest that
regional inundation of the inland area from Yuma, Arizona, north to the
Nevada border during the Miocene Epoch correlates with a single
maternal ancestor of the Mojave population of desert tortoises, which
would have presented significant isolation long enough to allow such
genetic divergence between these two populations.
Evaluation of Discreteness
The population of desert tortoises in the Black Mountains of Mohave
County, Arizona, which possess a uniquely Mojavean genotype, present an
anomaly in the argument for genetic divergence as a result of regional
inundation and subsequent isolation. McLuckie et al. (1999) suggest
three possible hypotheses that may have led to the occurrence of the
Mojave genotype east of the Colorado River: (1) active dispersal from
north of the Miocene Epoch inundation; (2) river meander and subsequent
geomorphological features assisted in allowing tortoises to cross the
river over time; and (3) aboriginal human transport across the river
for food stock, ritualistic or ceremonial use, or for medicinal uses
which may have resulted in released animals or escapes.
The genetic differentiation between the entire Mojave and Sonoran
populations of the desert tortoise has led some researchers to
hypothesize that the two populations may represent different species
entirely (Berry et al. 2002; Murphy et al. 2007). The Sinaloan
population of desert tortoise, has been documented to have a 4.2
percent divergence in genotype from the Sonoran desert tortoise, and a
5.1 percent divergence in genotype from the Mojave population of desert
tortoise (Lamb and McLuckie 2002). Lamb and McLuckie (2002) stated,
``Given their geographic distribution, genealogical depth, and
concordant suite of characters, the Mohave, Sonoran, and Sinaloan
tortoise assemblages clearly qualify as [evolutionarily significant
units].''
We have reviewed the information presented in the petition, and
have evaluated the information in accordance with 50 CFR 424.14(b). On
the basis of our review, we find that the petition provided substantial
information indicating that the Sonoran population of the desert
tortoise as it occurs east and south of the Colorado River, south to
the Yaqui River, in Sonora, Mexico, may be discrete from the Mojave and
Sinaloan desert tortoise populations. We base this conclusion on
ecological (habitat use), physiological (reproductive capacity),
morphological (shell dimensions), and behavioral (seasonal activity
patterns) differences that are further supported by analysis of genetic
polymorphisms that concluded significant divergence has occurred among
the Mojave, Sonoran, and Sinaloan populations of the desert tortoise
over time.
Significance
Under our DPS Policy, in addition to our consideration that a
population segment is discrete, we consider its biological and
ecological significance to the taxon to which it belongs. This
consideration may include, but is not limited to: (1) evidence of the
persistence of the discrete population segment in an ecological setting
that is unique or unusual for the taxon; (2) evidence that loss of the
population segment would result in a significant gap in the range of
the taxon; (3) evidence that the population segment represents the only
surviving natural occurrence of a taxon that may be more abundant
elsewhere as an introduced population outside its historical range; and
(4) evidence that the discrete population segment differs markedly from
other populations of the species in its genetic characteristics (61 FR
4721; February 7, 1996).
Information Provided in the Petition on Significance
The current range of the Sonoran desert tortoise, as described in
the discussion above pertaining to discreteness, represents several
hundred miles or kilometers of occupied habitat spanning across an
International Border. The petition contends that this population
segment is confined by two large perennial rivers; the Colorado River
in its northern periphery, which separates the Mojave and Sonoran
populations of desert tortoises, and the Yaqui River at its southern
periphery, which separates the Sonoran and Sinaloan populations of the
desert tortoise. These two rivers represent significant biogeographical
barriers to genetic exchange between adjacent population segments and,
therefore, preclude recolonization of this expanse of habitat from
adjacent populations should the Sonoran desert tortoise become
extirpated. As a result, the loss of the Sonoran desert tortoise would
constitute a significant gap of several hundred miles or kilometers in
the range between the Mojave and Sinaloan populations of desert
tortoises.
[[Page 44340]]
Evaluation of Significance
We have reviewed the information presented in the petition, and
have evaluated the information in accordance with 50 CFR 424.14(b). On
the basis of our review, we find that the petition provided substantial
information indicating that the Sonoran desert tortoise may be
significant to the continued existence of the taxon. We base this
conclusion on the large geographic range of the species, which may be
significant to the taxon as a whole, a gap of several hundred miles or
kilometers that would result from the loss of the Sonoran population,
which would effectively bisect the species' range, and the genetic
divergence between the three populations. These factors indicate that
the loss of the Sonoran population may result in a significant gap in
the range of the taxon that could not be filled over time due to
presence of biogeographical barriers to movement.
DPS Conclusion
We have reviewed the information presented in the petition, and
have evaluated the information in accordance with 50 CFR 424.14(b). In
a 90-day finding, the question is whether a petition presents
substantial information that the petitioned action may be warranted.
Based on our review, we find that the petition, supported by
information in our files, presents substantial scientific or commercial
information to demonstrate that the Sonoran population of desert
tortoise may be discrete from the Mojave and Sinaloan populations and
that the Sonoran population may be significant to the taxon as a whole.
As a result, we have determined that the Sonoran population of desert
tortoise may be a DPS. Thus, the Sonoran population of desert tortoise
may be a listable entity under the Act.
Five-Factor Evaluation
We next evaluated the level of threat to the potential DPS based on
the five listing factors established by the Act. We thus proceeded with
an evaluation of information presented in the petition, as well as
information in our files, to determine whether there is substantial
scientific or commercial information indicating that listing this
population may be warranted.
Section 4 of the Act (16 U.S.C. 1533), and its implementing
regulations at 50 CFR 424, set forth the procedures for adding species
to the Federal List of Endangered and Threatened Wildlife and Plants. A
species, subspecies, or distinct population segment of vertebrate taxa
may be determined to be endangered or threatened due to one or more of
the five factors described in section 4(a)(1) of the Act: (A) The
present or threatened destruction, modification, or curtailment of
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 90-day finding, we evaluated whether information
regarding the Sonoran desert tortoise, as presented in the petition and
other information available in our files, is substantial, thereby
indicating that the petitioned action may be warranted. Our evaluation
of this information is presented below. The information discussed below
was presented by the petitioners, unless otherwise noted.
A. Present or Threatened Destruction, Modification, or Curtailment of
the Species' Habitat or Range
Information Provided in the Petition
The petition states that habitat occupied by the Sonoran desert
tortoise is threatened by livestock grazing, urbanization and
development, mining, and international border patrol activities.
The petitioners claim that livestock grazing in occupied habitat
adversely affects the Sonoran desert tortoise in a number of ways
including competition for forage, vegetative trampling, alteration of
plant community structure, introducing or enhancing the establishment
of nonnative plant species, altering fire ecology, damaging burrows and
cover sites, and altering tortoise behavior (Bostick 1990; Fleischner
1994; Oldemyer 1994; Averill-Murray 2000b; Kazmaier et al. 2001;
Boarman 2002; Esque et al. 2002). Over 60 percent of habitat occupied
by the Sonoran desert tortoise occurs on federally managed land, the
majority of that on lands managed by the U.S. Bureau of Land Management
(BLM). The petitioners claim that on BLM land livestock grazing occurs
on 78 percent (on 273 allotments) of potentially occupied habitats for
the Sonoran desert tortoise. The petitioners also state that on U.S.
Forest Service lands, livestock grazing occurs on 86 percent of
potentially occupied habitat for the Sonoran desert tortoise. The
percentage of Sonoran desert tortoise habitat used for livestock
grazing on State, private, or tribal lands is not identified in the
petition.
The petitioners claim that the Sonoran desert tortoise and its
habitat are harmed by urbanization and development in approximately 29
percent of its occupied range in the United States. The petitioners
state that urbanization and development threaten the Sonoran desert
tortoise and its habitat. Tortoise habitat within developing areas may
be permanently lost or degraded, while patterns of development may
fragment habitat, restrict gene flow, and hamper recolonization of
formerly occupied habitat.
The human population in Arizona increased by 394 percent from 1960
to 2000; Arizona is the second-fastest growing State in terms of human
population (Social Science Data Analysis Network 2000, p. 1). In
particular, certain counties with habitat occupied by the Sonoran
desert tortoise have experienced explosive human population growth over
this timeframe: Maricopa (463 percent); Yavapai (579 percent); and
Mohave (2,004 percent) (Social Science Data Analysis Network 2000). The
petition did not specifically discuss the threat of urbanization and
development in occupied habitat for the Sonoran desert tortoise in
Mexico; however, information in our files suggests urbanization and
development might affect the Sonoran desert tortoise there as well.
Information in our files indicates that Mexico's human population grew
700 percent from 1910 to 2000 (Miller et al. 2005, p. 60). Demand from
a growing human population has spurred the need for more agricultural
development, according to information from our files (Contreras
Balderas and Lozano 1994, p. 384; va Linda et al. 1997, p. 316).
The petitioners provided evidence that mining activities may also
be a threat to the Sonoran desert tortoise and its habitat. Mining
activities occur on Federal and private lands but are stated to be the
most pervasive on BLM lands, with 4,670 mining claims occurring in
habitat occupied by the Sonoran desert tortoise. As of 2003, 1,096 of
these claims remained active and 3,574 had been closed, according to
the petitioners. The petitioners state that mining activities (both
small- and large-scale) adversely affect the Sonoran desert tortoise
through habitat fragmentation, loss, and degradation; introduction of
contaminants and fugitive dust (dust that cannot be attributed to a
single point of origin, such as a smokestack); off-road travel
associated with mining activities or roads created for said activities;
and entrapment of tortoises in mine spoil
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heaps (Averill-Murray 2000b; Woodman et al. 2001, 2004; Boarman 2002).
Occupied habitat for the Sonoran desert tortoise occurs along the
International Border in Yuma, Pima, and Santa Cruz counties in Arizona.
The petitioners state that patrol activities on the international
border present threats to the Sonoran desert tortoise and its habitat.
Specifically, the petitioners state that border patrol activities
threaten the Sonoran desert tortoise and its habitat through road
mortality, and loss or degradation of occupied habitat. In particular,
the petitioners claim that the recently constructed border fence
fragments the habitat of Sonoran desert tortoise populations in Mexico
and the United States, and also directly and indirectly threatens the
Sonoran desert tortoise habitat from construction and maintenance
activities associated with the border fence.
Evaluation of Information
In consideration of the threats summarized above and discussed in
the petition, we find that the petition provides substantial
information that listing the Sonoran desert tortoise due to the present
or threatened destruction, modification, or curtailment of its habitat
or range may be warranted.
B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
Information Provided in the Petition
The petition claims that the Sonoran desert tortoise is threatened
by poaching, illegal collection for use as pets, shooting, and
vandalism (physical harassment or disturbance of the animals)
throughout its range in the United States and Mexico. Illegal
collection of desert tortoises for food, for commercial trade, and as
pets has been documented (Fritts and Jennings 1994, Averill-Murray
2000b; Bury et al. 2002). Information in our files suggests that the
simple act of handling a Sonoran desert tortoise may cause an
individual tortoise to void the contents of its bladder in defense.
This loss of water may jeopardize its life (Averill-Murray 2002, p.
434; Boarman 2002). Shooting and vandalism of Sonoran desert tortoises
has been reported in Howland and Rorabaugh (2002) and Woodman et al.
(2002).
Evaluation of Information
In our evaluation of the petition, we find that the petitioners
provided substantial information that listing the Sonoran desert
tortoise due to overutilization for commercial, recreational,
scientific, or educational purposes may be warranted.
C. Disease or Predation
Information Provided in the Petition
The petitioners cite upper respiratory tract disease (URTD) as a
threat to the Sonoran desert tortoise and reference the significant
threat URTD is, and has been, for the Mojave population; a primary
reason that population was listed as threatened in 1990. This disease
is irreversible and fatal once acquired. Two species of Mycoplasma (a
genus of small parasitic bacteria that lack cell walls and can survive
without oxygen), Mycoplasma agassizii and M. testudineum, are known to
cause URTD in desert tortoises and are easily transmitted between
individual tortoises from casual contact (Brown et al. 1999; Wendland
et al. 2007). Appendix 2 of the petition summarizes disease incidence
reports within Sonoran desert tortoise populations. The petitioners
state that Sonoran desert tortoises have tested positive for one or
both of these antibodies at Saguaro National Park, and in the Ragged
Top, Hualapai, Harcuvar, Little Shipp, and Sand Tank mountains among
other locations. Dickinson et al. (2002) suspected that URTD may not be
as serious a threat to the Sonoran population of desert tortoises as it
has been for the Mojave population because tortoises in the Sonoran
population do not occur in as high of densities as those in the Mojave
and because Sonoran populations are more isolated from one another. In
addition, the Sonoran population can take advantage of a bimodal
precipitation cycle (two distinct rainy seasons). This offers
additional opportunities for rehydration, lessening physiological
stress, and, therefore, lessening susceptibility to the disease.
In addition to URTD, cutaneous dyskeratosis (shell disease) has
been observed in numerous Sonoran desert populations (Appendix 2 of the
petition). The petitioners claim that, while no serious deleterious
effects of the disease have been observed in affected tortoises, Homer
et al. (2001) indicated higher mortality rates in some populations
where the disease has been documented. Lastly, the petitioners state
that additional pathogens have been noted in free-ranging Sonoran
desert tortoises including Pasteurella sp., Streptococcus sp.,
Staphylococcus sp., herpesvirus, Pseudomonas sp., and Salmonella sp.
and that these diseases may be correlated with physiological stress
induced by habitat destruction and modification discussed above in
Factor A (Pettan-Brewer et al. 1996; Dickinson et al. 2001).
There are numerous natural predators of the Sonoran desert
tortoise, including the jaguar (Panthera onca) and mountain lion (Felis
concolor) (the only predators known to be able to break an adult
tortoise's shell), coyote (Canis latrans), common raven (Corvus corax),
kit fox (Vulpes macrotis), bobcat (Lynx rufus), gray fox (Urocyon
cinereoargenteus), badger (Taxidea taxus), Gila monster (Heloderma
suspectum), golden eagle (Aquila chrysaetos) and other raptors, greater
roadrunner (Geococcyx californianus), coachwhip (Coluber flagellum),
gophersnake (Pituophis melanoleucus), and kingsnake (Lampropeltis
getula) (Averill-Murray et al. 2002b). The petitioners state that urban
encroachment within the distribution of the Sonoran desert tortoise has
created, or threatens to create, elevated levels of unnatural
predation, mainly by ravens, coyotes, and feral domestic dogs. As
explained below, petitioners claim these predators have benefitted, or
been ``subsidized,'' by human activities within the wild-urban
interface areas.
Ravens can effectively prey on juvenile tortoises because their
shells have not yet hardened (particularly the plastron) and the ravens
are able to pierce the shells (Boarman 2002). Ravens, noted as a
significant threat to desert tortoises in the Mojave population, have
increased their numbers 14-fold within Arizona (Appendix 3 of the
petition; Boarman and Kristen 2008). The petitioners suggest that
increases in the number of ravens within the Sonoran desert may be
linked to increased availability of food and water resources at
landfills, rural and urban developments, along heavily traveled roads,
and at agricultural areas in particular dairies. These land uses were
also suspected by the petitioners to result in increased predation of
Sonoran desert tortoises from coyotes and feral dogs; the latter being
documented at 4 of 17 Sonoran desert tortoise study plots (Appendix 1
of the petition).
Evaluation of Information
In our evaluation of the petition, we find that the petitioners
provide substantial information that listing the Sonoran desert
tortoise due to the incidence of disease and high predation levels may
be warranted.
[[Page 44342]]
D. The Inadequacy of Existing Regulatory Mechanisms
Information Provided in the Petition
In 1988, the Sonoran and Mojave populations of the desert tortoise
were closed to collection in Arizona by the Arizona Game and Fish
Department, except as authorized under their scientific collecting
permit program. This status means that it is illegal to kill or capture
desert tortoises from the wild (unless under a special permit).
Possession for trade, sale, or other commercial purposes is prohibited
(Howland and Rorabaugh 2002). Prior to 1988, the Arizona Game and Fish
Department allowed the possession of one lawfully obtained tortoise per
person, which likely contributed to their popularity as pets (Averill-
Murray 2000b). The Arizona Game and Fish Department has developed a
draft Comprehensive Wildlife Conservation Strategy: 2005-2015, in which
the Sonoran desert tortoise has been identified as a Species of
Greatest Conservation Need for which immediate conservation is
necessary (Tier 1b under the Vulnerable category) (Arizona Game and
Fish Department 2006a, pp. 485-487; 2006b, p. 4). The Arizona Game and
Fish Department has been a significant contributor in the conservation
and management of the Sonoran desert tortoise, producing many documents
for public education, administering an adoption program for individual
Sonoran desert tortoises that cannot be returned to the wild, and
conducting or funding monitoring and research on wild Sonoran desert
tortoise populations (Arizona Game and Fish Department 1990, 1996,
2000, and 2004; Arizona Interagency Desert Tortoise Team 1996, 1997,
and 2000; Averill-Murray 2000).
The Sonoran desert tortoise does not currently have special status
under the Endangered Species Act. The desert tortoise is included in
Appendix I of the Convention on International Trade in Endangered
Species of Wild Fauna and Flora and a permit is required for the export
of tortoises (Howland and Rorabaugh 2002).
Several Federal agencies have management authority for Sonoran
desert tortoise habitat, including the BLM, the National Park Service,
the U.S. Forest Service, the U.S. Bureau of Reclamation, the U.S.
Department of Defense, and the Service. Significant land use
protections are afforded the Sonoran desert tortoise on National Park
Service lands and U.S. Fish and Wildlife Service refuges, in particular
where they occur adjacent to U.S. Department of Defense lands such as
the Barry M. Goldwater Range and the Yuma Proving Grounds, because of
the relatively large amounts of primarily undisturbed habitat within
the boundary zone between these managed lands.
The Sonoran desert tortoise is considered a ``sensitive species''
by the BLM. In 1988, the BLM adopted a rangewide management strategy
for desert tortoise habitat (BLM 1988; Howland and Rorabaugh 2002).
Subsequently, habitat for the Mojave and Sonoran populations of desert
tortoise was categorized into one of three categories: Category one
being the highest quality; Category three, the lowest. In 1991, the
BLM, the Service, and state wildlife agencies (Arizona, Nevada, Utah,
and California) developed a policy whereby persons who disturbed
occupied habitat were required to pay monetary compensation (usually in
the form of land acquisition). The monetary compensation was weighted
using the BLM's habitat categorization criteria. Mitigation ratios
ranged from 1:1 (acres protected: acres disturbed) for category three
habitat, to 6:1 for category one habitat (Howland and Rorabaugh 2002).
The petitioners also cite numerous reports, management strategies, and
formal actions taken by the BLM with regard to management of the
Sonoran desert tortoise, but conclude that, based on their review,
these measures may be insufficient to adequately protect the Sonoran
desert tortoise on BLM lands.
The Sonoran desert tortoise occurs on both the Tonto and Coronado
National Forests. The Sonoran desert tortoise is on the Regional
Forester's Sensitive Species List, which means it is considered in
land-management decisions. The petitioners claim that, despite this
recognition, threats to the Sonoran desert tortoise continue to occur
within these National Forests and that potential protections, such as
those afforded under the National Environmental Policy Act (42 U.S.C.
4321-4327), have failed to come to fruition, particularly with respect
to livestock grazing (see Table 6, p. 55 of the petition).
There are currently 10 Native American reservations within Arizona
that contain known or potential Sonoran desert tortoise habitat: Fort
Mojave Indian Tribe, Colorado River Indian Tribe, Hualapai Tribe, Fort
McDowell Yavapai Nation, Salt River Pima-Maricopa Indian Community,
Gila River Indian Community, Ak Chin, Tohono O'odham Nation, Pasqua
Yaqui Tribe, and San Carlos Apache Tribe, although the status of
populations on these reservations has not been established (Averill-
Murray 2000b). The petitioners state that historically no reservations
conducted surveys or performed active management for the Sonoran desert
tortoise or its habitat. However, the petitioners note that recently
the Tohono O'odham Nation developed the Wildlife and Vegetation
Management Program and now has oversight over the desert tortoise on
their land. This program authorizes surveys for Sonoran desert tortoise
and the establishment of monitoring plots, but does not provide funding
to implement these activities (Averill-Murray 2000b). The petitioners
also suggest that many Native American tribes have a historical
relationship with desert tortoises that is of important cultural and
spiritual significance, which may provide added protection of the
species on their lands (Nabhan 2002).
On State lands, the Arizona State Land Department manages occupied
Sonoran desert tortoise habitat, according to the petition, with the
goal of ``maximizing revenue to benefit education, health and penal
institutions,'' and works cooperatively with the Arizona Game and Fish
Department in management of Sonoran desert tortoises (Averill-Murray
2000b). Specifically, the petitioners state that the Arizona Game and
Fish Department ``recommends mitigation measures for tortoise impacts
for which it is consulted ... (and) comments on State land projects
related to urban planning, land sales and exchanges, rights of way, and
commercial leases,'' but these recommendations are not binding
(Averill-Murray 2000b).
The petition also notes that Pima County has considered the Sonoran
desert tortoise in its habitat conservation planning by acknowledging
that populations are decreasing in Pima County. However, Pima County
offers few specific protections for the species.
In Mexico, the Secretaria de Deserrollo Social lists both the
Sonoran and Sinaloan populations of the desert tortoise as threatened
(Secretaria de Deserrollo 2008, p. 99). Populations of the Sonoran
desert tortoise in Mexico are reportedly in decline. Factors believed
to contribute to this decline are related to lack of resources for
enforcement and include habitat destruction or modification, capture of
tortoises for food or pets, and predation by feral dogs (particularly
in areas adjacent to settlements or urban areas) (Fritts and Jennings
1994; Bury et al. 2002).
In the United States, as part of a multi-agency collaborative
project, the Arizona Interagency Desert Tortoise
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Team was formed in 1985 to coordinate research and management of
Sonoran desert tortoise populations in Arizona. Participating agencies
in the Arizona Interagency Desert Tortoise Team include the Arizona
Game and Fish Department, Arizona State Lands Department, the U.S.
Forest Service, the BLM, the U.S. Bureau of Reclamation, the U.S.
Bureau of Indian Affairs, the Service, the National Park Service, the
U.S. Geological Survey, and several U.S. Department of Defense military
reservations (Arizona Interagency Desert Tortoise Team 1996). Since its
inception, the Arizona Interagency Desert Tortoise Team has
collaborated in the development of numerous publically available
documents addressing conservation of the Sonoran desert tortoise
(Averill-Murray 2000a, 2000b; Arizona Game and Fish Department 2007a,
2007b; Arizona Interagency Desert Tortoise Team 2008).
The Arizona Interagency Desert Tortoise Team's Memorandum of
Understanding, signed in 1995, established specific objectives for the
team including: (1) ensuring the survival of the species; (2)
preventing loss of the species; and (3) improving the quality of
Sonoran desert tortoise habitat in Arizona, with the team to function
as an advocate for the Sonoran desert tortoise (Arizona Interagency
Desert Tortoise Team 1996). A management plan for the Sonoran desert
tortoise completed in 1996 called for improved monitoring protocols,
the implementation of threat-minimization activities, and the creation
of Sonoran Desert Management Areas for conservation of the Sonoran
desert tortoise (Arizona Interagency Desert Tortoise Team 1996).
However, the petitioners claim that the 1996 plan: (1) lacked
meaningful goals and objectives; (2) lacked political willpower without
legal protection for the Sonoran desert tortoise; (3) failed to
designate Sonoran Desert Management Areas; and (4) was poorly funded,
which hampered implementation of threat minimization activities
outlined in the plan. These shortcomings in the 1996 plan were
collectively recognized by the Arizona Interagency Desert Tortoise Team
members who in 2002 reconvened to initiate the development of a revised
plan in the form of a State Conservation Agreement for the Sonoran
desert tortoise. The State Conservation Agreement, when finalized, is
expected to: (1) mandate more practical conservation recommendations;
(2) garner a higher level of commitment and responsibility from its
signatories; (3) set measurable goals and objectives; and (4) establish
Key Habitat Areas on public lands where management strategies for the
Sonoran desert tortoise will focus.
Evaluation of Information
There are significant protections in place with respect to
management for the Sonoran desert tortoise on lands managed by the
Service, National Park Service, and to a lesser degree, lands managed
by the U.S. Department of Defense. The Arizona Interagency Desert
Tortoise Team has also provided technical expertise and guided habitat-
management decisions of participating agencies with marginal success.
Despite these protections, we conclude that the petition and
information in our files present substantial information that existing
regulatory mechanisms may be inadequate to prevent declines of the
Sonoran desert tortoise, particularly on lands managed as ``multiple-
use'' such as U.S. Forest Service, BLM, and the Arizona State Land
Department, where threats continue to occur. An additional concern is
the limited implementation of recommendations of the Arizona
Interagency Desert Tortoise Team's 1996 management plan.
In our evaluation of the petition, we find that the petitioners
provided substantial information that listing the Sonoran desert
tortoise due to the inadequacy of existing regulatory mechanisms may be
warranted.
E. Other Natural or Manmade Factors Affecting the Species' Continued
Existence
Information Provided in the Petition
The petitioners state that off-highway vehicle (OHV) use,
alteration of fire frequency in the Sonoran Desert resulting from
nonnative plant invasion, mortality on roads, drought, and climate
change are among additional threats to the Sonoran desert tortoise. The
petitioners claim that OHV use has increased significantly on public
lands within the distribution of the Sonoran desert tortoise,
especially on U.S. Forest Service and BLM lands, and particularly in
incised washes, which are important habitat for the Sonoran desert
tortoise (Averill-Murray 2000b; Averill-Murray and Averill-Murray 2002;
Riedle et al. 2008). We have information in our files that indicates
the use of OHVs has grown considerably in Arizona. For example, as of
2007, 385,000 OHVs were registered in Arizona (a 350-percent increase
since 1998) and 1.7 million people (29 percent of Arizona's population)
engaged in off-road activity from 2005-2007 (Sacco 2007). Over half of
OHV users reported that merely driving off-road was their primary
activity, versus using the OHV for the purpose of seeking a destination
to hunt, fish, or hike (Sacco 2007). Specific threats cited by the
petitioners to the Sonoran desert tortoise or its habitat from OHV use
include crushing tortoises, collapsing occupied and unoccupied burrows,
changes in plant abundance and species composition, reduced habitat
connectivity, soil compaction, soil erosion, reduced water
infiltration, higher soil temperatures, and increased fire-starts
(Boarman 2002; Ouren et al. 2007, pp. 6-7, 11, 16). The petitioners
further claims that OHV use causes destruction of cryptogamic soils,
which are soils with crusts formed by an association of algae, mosses,
and fungi, which stabilize desert soil, retain moisture, and protect
germinating seeds (Boarman 2002, pp. 46-47; Ouren et al. 2007, pp. 7-
8).
Nonnative plant species such as Mediterranean splitgrass (Schismus
barbatus), red brome (Brombus rubens), and African buffelgrass
(Pennisetum cilare) have significantly degraded Sonoran desert tortoise
habitat by out-competing more nutritional, native plant species and
altering the frequency and magnitude of wildfires in many areas within
its distribution (Howland and Rorabaugh 2002). The petitioners state
that in addition to injury and mortality of Sonoran desert tortoises,
wildfire within occupied habitat is expected to result in the complete
conversion of desertscrub to grasslands at higher elevations and to
barren landscapes at lower elevations (Esque et al. 2002). Pennisetum
cilare poses unique problems for the Sonoran desert tortoise in Sonora,
Mexico, because Sonoran desertscrub is actively cleared in favor of
planting P. cilare as forage for livestock; P. cilare disperses
naturally from these sites into adjacent habitat where it self-
perpetuates, and is ``likely to dominate the entire area'' (Bury et al.
2002).
The petitioners cite several adverse effects to the Sonoran desert
tortoise from roads. Among these threats were direct mortality, injury,
facilitation of increased raven populations, increased roadside
foraging by tortoises (as a result of increased plant growth from
precipitation runoff), population fragmentation, and contamination of
roadside habitat (Homer et al. 2001; Boarman 2002). Boarman and Kristin
(2008, Appendix 3 of the petition) states that roads are one of the
most prevalent threats in the study plots they reviewed.
Lastly, the petitioners claim that drought and climate change pose
additional threats to the Sonoran desert tortoise. Drought increases
the
[[Page 44344]]
physiological stress of desert tortoises and reduces reproductive rates
within populations because of reduced forage quality and abundance
(Averill-Murray and Klug 2000). The petitioners also state that the
effects of drought can act synergistically with other threats to the
Sonoran desert tortoise such as disease and habitat destruction or
modification. Increased magnitude and frequency of drought is expected
to occur as a result of climate change. Weiss and Overpeck (2005)
predict that the Sonoran Desert may be displaced in the south by
hotter, drier habitats and may expand to the north and to higher
elevations, displacing cooler, drier habitats. In our review of
available files, we find that Seagar et al. (2007, pp. 1181-1184)
analyzed 19 different computer models of differing variables to
estimate the future climatology of the southwestern United States and
northern Mexico in response to predictions of changing climatic
patterns. All but one of the 19 models predicted a drying trend within
the Southwest; one predicted a trend toward a wetter climate (Seagar et
al. 2007, p. 1181). A total of 49 projections were created using the 19
models and all but three predicted a shift to increasing aridity
(dryness) in the Southwest as early as 2021-2040 (Seagar et al. 2007,
p. 1181).
Evaluation of Information
In consideration of the above, we find that the petition and
information in our files provide substantial information to indicate
that OHV use, altered fire regimes, roads, and effects from prolonged
drought, exacerbated by climate change, may be threats to the Sonoran
desert tortoise.
Finding
On the basis of our determination under section 4 of the Act and
our evaluation of the five factors, we have determined that the
petition presents substantial information indicating that listing the
Sonoran population of desert tortoise may be warranted.
The petitioners presented substantial information indicating that
the Sonoran population of desert tortoise may be discrete and
significant and, therefore, may be a listable entity (DPS) under the
Act. Further, the petitioners presented substantial information that
the Sonoran population of desert tortoise may be threatened by Factors
A through E throughout the entire range, with the exception of Factor C
where the petitioners did not provide information on disease or
predation in Mexico, nor did we have information in our files on
disease or predation of the Sonoran desert tortoise in Mexico. Based on
this review and evaluation, we find that the petition has presented
substantial scientific or commercial information that listing the
Sonoran population of desert tortoise throughout its range in the
United States and Mexico as a DPS may be warranted due to current and
future threats presented in our discussion of the five listing factors.
As such, we are initiating a status review to determine whether listing
the Sonoran desert tortoise under the Act is warranted. We will issue a
12-month finding as to whether any of the petitioned actions are
warranted. To ensure that the status review is comprehensive, we are
soliciting scientific and commercial information regarding the Sonoran
desert tortoise, particularly with respect to its status and threats in
Mexico.
The ``substantial information'' standard for a 90-day finding
differs from the Act's ``best scientific and commercial data'' standard
that applies to a status review to determine whether a petitioned
action is warranted. A 90-day finding does not constitute a status
review under the Act. In a 12-month finding, we will determine whether
a petitioned action is warranted after we have completed a thorough
status review of the species, which is conducted following a
substantial 90-day finding. Because the Act's standards for 90-day and
12-month findings are different, as described above, a substantial 90-
day finding does not mean that the 12-month finding will result in a
warranted finding.
The petitioners requested that critical habitat be designated for
this DPS. If we determine in our 12-month finding that listing the
Sonoran population of desert tortoise is warranted, we will address the
designation of critical habitat to the maximum extent prudent and
determinable at the time of the proposed rulemaking.
References Cited
A complete list of all references cited is available, upon request,
from the Arizona Ecological Services Office (see FOR FURTHER
INFORMATION CONTACT).
Author
The primary authors of this notice are the staff members of the
Arizona Ecological Services Office (see FOR FURTHER INFORMATION
CONTACT).
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: August 19, 2009.
Daniel M. Ashe,
Director, U.S. Fish and Wildlife Service.
[FR Doc. E9-20835 Filed 8-27-09; 8:45 am]
BILLING CODE 4310-55-S