[Federal Register: February 7, 2006 (Volume 71, Number 25)]
[Proposed Rules]               
[Page 6241-6248]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]



Fish and Wildlife Service

50 CFR Part 17

Endangered and Threatened Wildlife and Plants; 90-Day Finding on 
a Petition to List the Gunnison's Prairie Dog as Threatened or 

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 90-day petition finding.


SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
90-day finding on a petition to list the Gunnison's prairie dog 
(Cynomys gunnisoni) as threatened or endangered under the Endangered 
Species Act of 1973, as amended (Act). We find that the petition does 
not present substantial scientific and commercial data indicating that 
listing the Gunnison's prairie dog may be warranted. Therefore, we will 
not be initiating a formal status review to determine if listing this 
species is warranted. We will work with the States where information is 
currently unavailable to develop information that will assist in 
determining and monitoring the status of Gunnison's prairie dog. Once 
those results are available we will reevaluate the status of Gunnison's 
prairie dog.

DATES: The finding announced in this document was made on January 30, 

ADDRESSES: The petition, supporting data, and comments will be 
available for public inspection, by appointment, during normal business 
hours at the South Dakota Ecological Services Office, 420 South 
Garfield Avenue, Suite 400, Pierre, South Dakota, 57501. Submit new 
information, materials, comments or questions concerning this taxon to 
the Field Supervisor at the above address.

FOR FURTHER INFORMATION CONTACT: Pete Gober, Field Supervisor, South 
Dakota Ecological Services Office at the above address (telephone 605-
224-8693; facsimile 605-224-9974).



    Section 4(b)(3)(A) of the Act (16 U.S.C. 1531 et seq.), requires 
that we make a finding on whether a petition to list, delist, or 
reclassify a species presents substantial scientific or commercial 
information indicating that the petitioned action may be warranted. We 
are to base this finding on information provided in the petition and 
other information that is readily available to us (e.g., in our files). 
To the maximum extent practicable, we are to make this finding within 
90 days of our receipt of the petition, and publish our notice of this 
finding promptly in the Federal Register.
    Our standard for substantial scientific information within the 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 information 
was presented, we are required to commence a review of the status of 
the species.
    In making this finding, we relied on information provided by the 
petitioners and information in our files, and evaluated that 
information in accordance with 50 CFR 424.14(b). Our process of coming 
to a 90-day finding under section 4(b)(3)(A) of the Act and Sec.  
424.14(b) of our regulations is limited to a determination of whether 
the information in the petition meets the ``substantial scientific 
information'' threshold.
    We do not conduct additional research to make a 90-day finding, nor 
do we subject the petition to rigorous critical review. Rather, as the 
Act and regulations contemplate, in coming to a 90-day finding, we 
acknowledge the petitioner's sources and characterizations of the 
information unless we have specific information to the contrary.
    Our 90-day findings consider whether the petition states a 
reasonable case for listing on its face. Thus, our finding expresses no 
view as to the ultimate issue of whether the species should be listed. 
We reach a conclusion on that issue only after a more thorough review 
of the species' status.


    On February 23, 2004, the Service received a petition of the same 
date, from Forest Guardians and 73 other organizations and individuals 
(Forest Guardians et al. 2004). This petition requested that the 
Gunnison's prairie dog (Cynomys gunnisoni), found in Arizona, Colorado, 
New Mexico, and Utah, be listed as threatened or endangered and that 
critical habitat be designated for the species.
    Action on this petition was precluded by court orders and 
settlement agreements for other listing actions that required nearly 
all of our listing funds for fiscal year 2004. On July 29, 2004, we 
received a 60-day notice of intent to sue (Forest Guardians et al. 
2004) for failure to complete a finding. On December 7, 2004, an 
amended complaint for failure to complete a finding for this and other 
species was filed (Biodiversity Conservation Alliance et al. 2004). We 
reached a settlement agreement with the plaintiffs for submittal to the 
Federal Register of a 90-day finding for the Gunnison's prairie dog by 
January 26, 2006. This notice constitutes our 90-day finding for the 
petition to list the Gunnison's prairie dog.

Species Information

    The Gunnison's prairie dog is a member of the Sciuridae family, 
which includes squirrels, chipmunks, marmots, and prairie dogs. Prairie 
dogs constitute the genus Cynomys. Taxonomists currently recognize 5 
species of prairie dogs belonging to 2 subgenera, all in North America 
(Goodwin 1995). The white-tailed subgenus, Leucocrossuromys, includes 
Utah (C. parvidens), white-tailed (C. leucurus), and Gunnison's prairie 
dogs (Goodwin 1995). The black-tailed subgenus, Cynomys, consists of 
Mexican (C. mexicanus) and black-tailed (C. ludovicianus) prairie dogs 
(Goodwin 1995). The number of chromosomes for the Gunnison's prairie 
dog (2n = 40) is different from all other prairie dog species (2n = 
50), suggesting the species' uniqueness and its early evolutionary 
divergence from other prairie dog species (Goodwin 1995; Pizzimenti 
    The Gunnison's prairie dog has sometimes been divided into 2 
subspecies: C. g. gunnisoni and C. g. zuniensis (Hollister 1916). The 
petition addressed the species, with no subspecies consideration. 
However, the petitioners later requested that the petition be 
considered to apply to both the full species and either of the 
subspecies (Rosmarino in litt. 2005). The most recent published 
analyses do not support subspecies designation (Goodwin 1995, 
Pizzimenti 1975), and this is position we currently hold. Research on 
the issue of subspeciation is ongoing (Hafner 2004; Hafner et al. 
    Gunnison's prairie dog adults vary in length from 309-373 
millimeters (mm) (12-15 inches (in)) and weigh 650-1200 grams (gm) (23-
42 ounces (oz)), with males averaging slightly larger than females 
(Hall 1981; Pizzimenti and Hoffman 1973). The dorsal color is yellowish 
buff intermixed with blackish hairs. The top of the head, sides of

[[Page 6242]]

cheeks, and ``eyebrows'' are noticeably darker than the dorsum (Hall 
1981; Pizzimenti and Hoffman 1973). The species differs from black-
tailed prairie dogs in having a much shorter and lighter colored tail 
and from other white-tailed species in having grayish-white hairs in 
the distal half of the tail rather than pure white (Hoogland 1995; 
Pizzimenti and Hoffman 1973).
    The onset of reproduction in Gunnison's prairie dogs is somewhat 
variable depending upon latitude, elevation, and seasonal variation, 
but most typically is April and May (Hoogland 1998, 2001). Females will 
breed as yearlings when resources are abundant (Goodwin 1995; Hall 
1981; Haynie et al. 2003; Hoogland 1998; Hoogland 2001; Pizzimenti and 
Hoffman 1973). A maximum of one litter is produced per year with a mean 
litter size of 3.77 (Hoogland 2001). Individuals live in family groups 
called clans; and adjacent clans constitute a colony (Fitzgerald and 
Lechleitner 1974). Clan members defend a home territory of 
approximately 2.5 acres (1 hectare), but commonly forage outside of 
home territory in the weakly defended peripheral sections of 
territories belonging to other clans (Hoogland 1998, 1999).
    Gunnison's prairie dog potential habitat includes level to gently 
sloping grasslands and semi-desert and montane shrublands, at 
elevations from 6,000-12,000 feet (ft) (1,830-3,660 meters (m)) (Bailey 
1932; Findley et al. 1975; Fitzgerald et al. 1994; Pizzimenti and 
Hoffman 1973; Wagner and Drickamer 2002). Grasses are the most 
important food item, with forbs, sedges, and shrubs also occasionally 
utilized (Pizzimenti and Hoffman 1973; Shalaway and Slobodchikoff 
1988). Individuals hibernate for as long as 7 months (Ecke and Johnsonn 
1952; Fitzgerald and Lechleitner 1974).
    The current distribution of the species is generally centered on 
the ``Four Corners'' region of northern Arizona, southwestern Colorado, 
northwestern New Mexico, and southeastern Utah (Anderson et al. 1986; 
Bailey 1932; Hall 1981; Knowles 2002; Pizzimenti and Hoffman 1973). 
There is some very limited overlap between ranges for Gunnison's 
prairie dogs and black-tailed prairie dogs in New Mexico (Goodwin 1995; 
Sager 1996), and between Gunnison's prairie dog and white-tailed 
prairie dog in Colorado (Knowles 2002), but we have no evidence that 
interbreeding is occurring. Using Geographic Information Systems (GIS) 
datasets and known habitat requirements, Seglund et al. (2005) estimate 
that 27 percent of potential Gunnison's prairie dog habitat occurs in 
Arizona, 25 percent in Colorado, 45 percent in New Mexico, and 3 
percent in Utah. Rangewide, approximately 73 percent of potential 
habitat occurs on tribal and private lands (Seglund et al. 2005). 
Significant portions of potential habitat occur on tribal lands, 
especially in Arizona and New Mexico. We contacted 29 Tribes and 
Pueblos within the Gunnison's prairie dog range to attain post-1961 
status information. We did not receive any formal responses from the 
tribes; no information is available regarding the status of the species 
on tribal lands.
    Of the documented range contractions, the most significant has 
occurred in Arizona. Gunnison's prairie dog was recorded in parts of 8 
Arizona counties in the early 20th century (Wagner and Drickamer 2002). 
In 1961, the species was documented in 5 counties (Bureau of Sport 
Fisheries and Wildlife 1961). More recent studies have observed 
occupied habitat in only the four northernmost counties (Roemer 1997; 
Wagner and Drickamer 2002). We are unable to determine what if any 
contraction is attributable to more recent population changes which 
would assist us in determining whether the species may be threatened.
    The best available information indicates that population densities 
of Gunnison's prairie dog colonies are variable, depending on 
environmental influences (including habitat, season, disease, and 
precipitation), as well as anthropogenic influences (such as chemical 
control and recreational shooting). Densities typically range from 2-23 
individuals per acre (ac) (5-57 per hectare (ha)) (Fitzgerald et al. 
1994), and are similar to densities in black-tailed prairie dog 
colonies (Cully 1993), which typically range from 2-18 individuals per 
ac (5-45 per ha) (Fagerstone and Ramey 1996; Hoogland 1995; King 1955; 
Koford 1958). Knowles (2002) notes historic densities for Gunnison's 
prairie dogs as high as 63 individuals per ac (156 per ha), but 
concludes that overall, they generally occur at lower densities than 
black-tailed prairie dog. In the available literature, prairie dog 
population abundance is most often discussed in terms of acres or 
hectares of occupied habitat rather than in numbers of individuals 
because of the wide range of observed population densities for the 
species, wide natural population fluctuations (due to drought, etc.) 
and the limited number of studies that have determined actual numbers 
of individuals in a population due to the significant additional cost 
and effort associated with doing so.
    We have several estimates of historic and more recent Gunnison's 
prairie dog occupied habitat are available from the four States within 
the species' range (Tables 1-3). These estimates span a time period 
from 1916 to the present. Different methodologies were used at 
different times and in different locales to derive the various 
estimates. However, these estimates represent the best available 
information and are comparable for the purpose of determining general 
population trends on the scale of order-of-magnitude changes. 
Methodologies have improved in recent years, with the advent of tools 
such as aerial survey, satellite imagery, and GIS. Consequently, 
estimates that utilize these tools can be expected to be more accurate.
    Only limited information is available regarding State-wide and 
range-wide historic estimates of occupied habitat. More accurate 
information is available regarding several smaller (more easily 
delineated) sites that have been monitored in recent years. All 
available estimates of occupied habitat are presented in the following 

State-Wide Estimates

    Information available regarding historic estimates of Gunnison's 
prairie dog occupied habitat is based largely on federal records from 
early poisoning efforts. Oakes (2000) used field survey and poisoning 
records from the Bureau of Biological Survey (a predecessor of the 
Service) to derive early estimates for occupied habitat in Arizona and 
New Mexico. Oakes (2000) estimated that in 1916, approximately 6.6 
million ac (2.7 million ha) of Gunnison's prairie dog occupied habitat 
occurred in Arizona and 11 million ac (4.4 million ha) in New Mexico. 
Oakes (2000) postulated that following poisoning efforts, there were 
approximately 6 million ac (2.4 million ha) of occupied habitat in 
Arizona and 9 million ac (3.6 million ha) of occupied habitat in New 
Mexico in 1921 (Table 1). No estimate of density or population 
associated with the habitat is available, due to the previously-
mentioned difficulty associated with determining population densities.
    We are not aware of any literature regarding historic estimates of 
occupied Gunnison's prairie dog habitat for Colorado or Utah. We 
derived approximate estimates in order to gain some perspective on the 
extent of historic decline. As noted previously, the estimates of 
historically (i.e., 1916) occupied habitat from Oakes (2000) were based 
on federally-directed state inventories and poisoning records. Seglund 
et al. (2005) used GIS datasets

[[Page 6243]]

that considered known habitat requirements regarding elevation, slope, 
and land cover to predict the potential habitat available in each 
state. Using the estimates of historically-occupied habitat from Oakes 
(2000) for Arizona and New Mexico and the relative percentages of 
potential habitat presented in Seglund et al. (2005), we derived 
estimates of historically-occupied (circa 1916) habitat for Colorado (6 
million ac / 2.4 million ha) and Utah (700,000 ac / 284,000 ha). 
Accordingly, the range-wide estimate for historic (circa 1916) 
Gunnison's prairie dog occupied habitat would be approximately 24 
million ac (9.7 million ha) (Table 1).
    We believe that these historic estimates are reasonable but also 
recognize that they are based on assumptions which could greatly 
influence the outcome of the estimate. Historic declines which occurred 
over the past 100 years do not provide an appropriate context for 
evaluating current threats to the species. These historic estimates are 
of limited value in determining the likely persistence of this species 
at present. The evaluation of whether or not a specific threat rises to 
the level of threatening a species should be based on ongoing and 
likely future impacts.
    In 1961, the Bureau of Sport Fisheries and Wildlife (also a 
predecessor of the Service) tabulated habitat estimates on a county-by-
county basis throughout the range of all prairie dog species in the 
western United States. This survey was in response to concerns from 
within the agency regarding possible adverse impacts to prairie dogs 
from poisoning (Oakes 2000). In State-wide summaries, the agency 
estimated approximately 445,000 ac (180,000 ha) of Gunnison's prairie 
dog occupied habitat in Arizona, 116,000 ac (47,000 ha) in Colorado, 
355,000 ac (144,000 ha) in New Mexico, and 100,000 ac (41,000 ha) in 
Utah (Bureau of Sport Fisheries and Wildlife 1961). The total range-
wide estimate for Gunnison's prairie dog occupied habitat in 1961 was 
approximately 1 million ac (405,000 ha) (Table 1).
    The estimates of historic habitat compared to the 1961 data suggest 
that, from 1916 to 1961, Gunnison's prairie dog habitat and thus 
populations decreased by approximately 93 percent in Arizona, 98 
percent in Colorado, 97 percent in New Mexico, and 86 percent in Utah, 
or by approximately 95 percent range-wide. While the magnitude of the 
habitat losses require a conclusion that overall populations declined 
as well, this decline does not necessarily lead to a conclusion that 
current populations continue to decline.
    All four States within the range of the Gunnison's prairie dog 
assert in their Comprehensive Wildlife Conservation Strategies that the 
species is at risk, declining, and deserving of special management 
consideration (Seglund et al. 2005). These Strategies were developed by 
the States in response to Congressional funding and provide guidance 
for future conservation efforts between Federal, tribal, State, local, 
and private entities. The strategies focus on species in greatest need 
of conservation. However, since less than one year has elapsed since 
they were completed, an evaluation of their effectiveness cannot yet be 
made. Based upon the information available in our files, Colorado is 
the only state with a Gunnison's prairie dog population estimate 
derived from a recent, State-wide field effort (Skiba, in litt. 2005). 
Other recent State-wide estimates appear to be based on extrapolations 
(e.g., Bodenchuck (1981) for New Mexico and Colorado Department of 
Agriculture (1990) for Colorado), or are minimum estimates obtained 
from summing known, site-specific data (e.g., Knowles (2002) for New 
Mexico and Utah, Seglund et al. (2005) for New Mexico and Utah, and Van 
Pelt in litt. (2005) for Arizona).
    In Arizona, it is estimated that occupied habitat on non-tribal 
lands was approximately 100,000 ac (40,500 ha) in 2005 (Van Pelt in 
litt. 2005) (Table 1). Approximately 50 percent of potential habitat is 
on tribal lands in Arizona; consequently, a current state-wide estimate 
in Arizona is likely substantially more than the 100,000 ac (40,500 ha) 
reported by Van Pelt (in litt. 2005), although no comprehensive data 
from tribal lands are available. Occupied habitat on non-tribal lands 
State-wide appears to have increased from 10,000 ac (4,000 ha) in 1961 
(Bureau of Sport Fisheries and Wildlife 1961) to 100,000 ac (40,500 ha) 
in 2005 Van Pelt (in litt. 2005). We have no data regarding, recent 
population trends on tribal lands State-wide. However, we are unaware 
of any disproportionate adverse effects to the species on tribal lands 
during this interval. Thus, we have assumed that the amount of habitat 
on tribal lands remained constant from 1961 to 2005 (Table 1). This 
assumption seems reasonable, particularly in light of the fact that 
occupied lands have increased ten-fold on non-tribal lands.
    The Colorado Department of Agriculture (CDA 1990) solicited 
questionnaire responses from farmers and ranchers and thereafter 
extrapolated an estimate of 1,553,000 ac of occupied habitat for all 3 
species of prairie dogs found in Colorado. Based upon species 
occurrence by county, Seglund et al. (2005) derived a state-wide 
estimate from the CDA (1990) data of 439,000 ac (178,000 ha) of 
Gunnison's prairie dog occupied habitat in 1990 (Table 1). However, 
other, more recent estimates based on field work may provide the best 
evidence of occupied habitat (population) trends for this species in 
recent years in Colorado. In 2005, the Colorado Division of Wildlife 
estimated 174,000 ac (70,000 ha) of Gunnison's prairie dog occupied 
habitat State-wide, based upon their own field surveys and reports from 
field personnel from other agencies (Skiba, in litt. 2005) (Table 1). 
State-wide occupied habitat since 1961 appears to have remained stable 
or increased somewhat, from 116,000 ac (55,000 ha) in 1961 to 174,000 
ac (70,000 ha) in 2005.
    In New Mexico, Bodenchuck (1981) solicited questionnaire responses 
from agricultural producers. Respondents reported 107,574 ac (43,567 
ha) of Gunnison's prairie dog occupied habitat. Bodenchuck (1981) 
extrapolated a State-wide total of 348,000 ac (141,000 ha) of occupied 
habitat for the species (Table 1). Oakes (2000) questioned this 
extrapolation because of possibly faulty assumptions used to derive it. 
Knowles (2002) estimated that 75,000 ac (30,000 ha) of occupied habitat 
existed in 1982 (Table 1). Seglund et al. (2005) reported that New 
Mexico Game and Fish utilized Digital Orthophoto Quarter Quadrangles to 
estimate a minimum of 9,108 ac (3,689 ha) of occupied habitat state-
wide in 2004 (Table 1). State-wide occupied habitat may have been in a 
decreasing trend, from 355,000 ac (144,000 ha) in 1961 to a minimum of 
9,000 ac (4,000 ha) in 2004.
    In Utah, Seglund et al. (2005) reported that the Utah Division of 
Wildlife estimated that the State had 22,007 ac (8,906 ha) of occupied 
Gunnison's prairie dog habitat in 1968 (Table 1). Knowles (2002) 
estimated a minimum of 3,678 ac (1,490 ha) of occupied habitat State-
wide (Table 1). The state-wide trend in occupied habitat since 1961 
appears to have been decreasing, from 100,000 ac (40,500 ha) in 1961 to 
4,000 ac (2,000 ha) in 2002.

[[Page 6244]]

              Table 1.--State-Wide Occupied Habitat Estimates (in acres) for Gunnison's Prairie Dog
                 State                       1961                   Recent               Trend, 1961 to present
Arizona...............................         445,000  ~535,000.....................  Increasing.
Colorado..............................         115,650  439,000 (CO DOA 1990) 174,224  Increasing.
                                                         (CO DOW 2005).
New Mexico............................         354,905  348,000 (Bodenchuk 1981)       Decreasing?
                                                         75,000 in 1982 (Knowles
                                                         2002) >9,108 (Seglund et al.
Utah..................................         100,000  22,007 in 1968 (Seglund et     Decreasing?
                                                         al. 2005) >3,678 (Knowles
    Total.............................       1,015,945  ~722,000 (assuming no change
                                                         in the amount of occupied
                                                         habitat on AZ tribal lands
                                                         since 1961).

Range-Wide Estimates

    Gunnison's prairie dog populations in all states within the 
species' range have declined significantly in a historic sense, but may 
have been relatively more stable in some States in recent decades. 
Regardless of the absolute accuracy of historic estimates of occupied 
habitat for the individual States, it is apparent that Gunnison's 
prairie dog occupied habitat has declined range-wide (Table 1). 
Differing survey and analytical methods, along with unknown confidence 
intervals prevents us from being able to compare estimates through time 
and among localities. Point estimates (Table 1) for New Mexico (Seglund 
et al. 2005) and for Utah (Knowles 2002) are estimated minimums.

Site-Specific Estimates

    In addition to State-wide and range-wide estimates, we also 
evaluated site-specific estimates of occupied habitat, and considered 
this information in our conclusions regarding current population 
trends. Site-specific estimates of occupied habitat are typically 
derived from field surveys related to monitoring and/or research, 
rather than extrapolation. The smaller size of a study site versus a 
state-wide also lends itself to more precise assessment. Consequently 
site-specific estimates are often more accurate than state-wide 
estimates. Site-specific estimates are also often more recent and 
therefore provide additional insight into current trends. However, an 
inherent bias in evaluating prairie dog population trends may exist 
because dramatic declines or increases in existing colonies may be more 
likely to be reported than the establishment of new populations in 
previously uninhabited areas. In addition, monitoring programs tend to 
focus more on established sites than on identifying new occupied sites.
    All site-specific estimates that we are aware of are listed in 
Table 2. As noted in the following text, all site-specific estimates, 
with the exception of Aubrey Valley in Arizona, indicate declines in 
occupied habitat due to plague epizootics. In addition to State-wide 
and site-specific estimates, there are several sites that have been 
studied and described in terms of numbers of colonies. While these 
sites do not provide precise data in terms of acres of occupied 
habitat, they provide additional insight into the likely extent of 
impact from sylvatic plague throughout the range of the Gunnison's 
prairie dog (Table 3). It should be noted that for most sites described 
in Tables 2 and 3, estimates are not available from the past year, so 
the current status of these sites is not known. In addition, the basis 
of the estimates vary, the relative rigor of the estimates vary from 
published papers to verbal estimates. Notwithstanding the variance in 
methodology and level of rigor it is apparent that plague can result in 
devastating population effects to individual populations and colonies.

                                Table 2.--Site-Specific Occupied Habitat Estimates (in acres) for Gunnison's Prairie Dog
                Site                        Estimate                Estimate               Estimate               Estimate                Status
Aubrey Valley, AZ..................  ......................  19,368 in 1990         29,653 in 1997         42,000 in 2005 (Van    Increasing.
                                                              (Seglund et al.        (Winstead in litt      Pelt, pers.comm.
                                                              2005).                 2002).                 2005).
Dilkon, AZ.........................  ......................  .....................  8,650 in 1994 (Wagner  43 in 2001 (Wagner     Decreasing.
                                                                                     2002).                 2002).
Currecanti Natl. Rec. Area, CO.....  ......................  148 in 1980 (Rayor     100% mortality by      .....................  Decreasing.
                                                              1985).                 1981 (Rayor 1985).
Gunnison, Saguache, Montrose Co.,    ......................  .....................  15,569 in 1980         770 in 2002 (Capodice  Decreasing.
 CO.                                                                                 (Capodice & Harrell    & Harrell 2003).
South Park, CO.....................  915,000 in 1945 (Ecke   74,000 in 1948         None known in 1977     42 in 2002 (CO DOW     Decreasing.
                                      & Johnson 1952).        (Fitzgerald 1993).     (Fitzgerald 1993).     2002).
Catron & Socorro Co., NM...........  2,458,650 in 1916       .....................  >12,000 in 1984 (Luce  >6,000 in 2005 (Luce   Decreasing.
                                      (Oakes 2000).                                  2005).                 2005).
Moreno Valley, NM..................  ......................  11,000 in 1984 (Cully  >99% mortality by      .....................  Decreasing.
                                                              et al. 1997).          1987 (Cully et al.

                 Table 3.--Site-Specific Estimates of Colony Numbers for Gunnison's Prairie Dog
                Site                          Estimate                 Estimate                  Status
Flagstaff, AZ.......................  75 colonies in 2000      14 colonies in 2001      Decreasing.
                                       (Wagner & Drickamer      (Wagner & Drickamer
                                       2002).                   2002).
Petrified Forest NP, AZ.............  8 colonies in 1994       3 colonies in 1996       Decreasing.
                                       (Turner 2001).           (Turner 2001).

[[Page 6245]]

Seligman, AZ........................  47 colonies in 1990      11 colonies in 2001      Decreasing.
                                       (Wagner & Drickamer      (Wagner & Drickamer
                                       2002).                   2002).
Chubbs Park, CO.....................  1 colony in Aug., 1958   100% mortality in        Decreasing.
                                       (Lechleitner et al.      Sept., 1959
                                       1962).                   (Lechleitner et al.
Navajo Nation in NM.................  625 colonies in 1966     233 colonies in 1969     Decreasing.
                                       (Fitzgerald 1970).       (Fitzgerald 1970).
Garfield Co., UT....................  1 colony in 1980         100% mortality in 1981   Decreasing.
                                       (Barnes 1993).           (Barnes 1993).

    The Dilkon area on the Navajo Reservation in Arizona had 8,650 ac 
(3,500 ha) of occupied habitat in 1994 and apparently decreased to 43 
ac (17 ha) in 2001 (Wagner 2002) following a plague epizootic (Table 
2). Other sites in Arizona, where only the number of colonies were 
noted (Table 3) include: 8 colonies in Petrified Forest National Park 
in 1994, with 5 colonies extirpated following a plague epizootic in 
1995 and 1996 (Turner 2001); 75 active colonies in the Flagstaff area 
in 2000, reduced to 14 active colonies in 2001 following a plague 
epizootic (Wagner and Drickamer 2002); and 47 active colonies in the 
Seligman area, covering approximately 9,000 ac (3,500 ha) were reduced 
to 11 active colonies in 2001 following a plague epizootic (Wagner and 
Drickamer 2002).
    In Colorado, a 148-ac (60-ha) colony in Curecanti National 
Recreation Area experienced 100 percent mortality following a plague 
epizootic in 1981 (Rayor 1985) (Table 2). In South Park, Colorado, 
there were an estimated 915,000 ac (371,000 ha) of occupied habitat in 
1945 (Ecke and Johnson 1952) and 74,000 ac (30,000 ha) in 1948 
(Fitzgerald 1993). Fitzgerald (1993) could not locate any colonies in 
South Park in 1977, but 42 ac (17 ha) of occupied habitat were located 
in 2002 (Colorado Division of Wildlife 2002) (Table 2). South Park 
experienced a remarkable decrease in occupied habitat from 1945 to 
2002, due predominantly to plague. Another site in Colorado where only 
the number of colonies was noted (Table 3), is a colony in Chubbs Park, 
Chaffee County, which experienced 100 percent mortality in 1959 
following a plague epizootic (Kartman et al. 1962 and Lechleitner et 
al. 1962).
    In Moreno Valley, New Mexico, Cully (1991) estimated that there 
were 11,000 ac (4,500 ha) of occupied habitat in 1984; and in 1987, 
after two plague epizootics, there was a significant decrease, with 
greater than 99.5 percent mortality (Cully et al. 1997) (Table 2). 
Another site in New Mexico where only the number of colonies was noted, 
is the New Mexico portion of the Navajo Nation (Table 3), where the 
number of known colonies dropped from 625 in 1966 to 233 in 1969 
following repeated epizootics (Fitzgerald 1970).
    In Utah, a colony in Garfield County experienced 100 percent 
mortality following a plague epizootic in 1981 (Barnes 1993) (Table 3).

Threats Analysis

    In the following narrative, we discuss each of the major assertions 
made in the petition, organized by the five listing factors found in 
section 4(a)(1) of the Act. A species may be determined to be 
endangered or threatened if it meets the definition specified in the 
Act pursuant to an evaluation of the following five threat factors: (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) 
inadequacy of existing regulatory mechanisms; or (E) other natural or 
manmade factors affecting its continued existence. In making this 
finding, we evaluated whether impacts to the Gunnison's prairie dog 
presented in the petition and other information readily available in 
our files present substantial information that listing may be 
warranted. Our evaluation of these factors is presented below.

A. Present of Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

Information Provided in the Petition
    The petition asserts that habitat loss and fragmentation has 
imperiled the Gunnison's prairie dog. The petitioner has documented, 
through personal observation, the loss of 745 ac (302 ha) of occupied 
habitat due to municipal development in Santa Fe, Albuquerque, Taos, 
and Flagstaff. The petition documents that poor rangeland management 
(primarily via overgrazing) has resulted in the proliferation of 
noxious weeds, especially cheatgrass (Bromus tectorum), that has in 
turn affected native vegetation. The petition asserts that loss of 
native vegetation may diminish habitat suitability for Gunnison's 
prairie dog. The petition notes that the proliferation of cheatgrass 
has resulted in the alteration of fire ecology, and asserts that it has 
in turn degraded prairie dog habitat. The petition asserts that the 
transfer of public lands (privatization) threatens the species. The 
petition presents an inventory of land parcels leased for oil and gas 
exploration and development and asserts that this activity threatens 
the species. The petition asserts that road mortality threatens the 
species. The petition asserts that all factors affecting the Gunnison's 
prairie dog result in isolation and fragmentation of remnant colonies, 
and that these smaller, isolated colonies are more susceptible to local 
extirpation by other factors such as poisoning and plague.
Evaluation of Information in the Petition
    Although municipal development may have adverse impacts on some 
Gunnison's prairie dog populations at a local scale, we do not have 
substantial information that it causes range-wide population declines. 
Seglund et al. (2005) determined that urbanization affects 577,438 ac 
(233,681 ha) within the range of the species. This is less than 2 
percent of the potential habitat within the range of the species. 
Wagner (2002) noted that in Arizona, human development undoubtedly 
impacts local populations of Gunnison's prairie dogs near the few 
cities and agricultural areas in northern Arizona, but the impact on 
overall populations is probably quite small. The petition did not 
present substantial scientific information that habitat loss and 
fragmentation is threatening the species.
    We are aware of reports that noxious weeds increase in the presence 
of overgrazing. However, based upon the information in our files, the 
impact of overgrazing on prairie dog populations is contradictory. Some 
reports have noted that species density is positively correlated with 
the number of native plants (Shalaway and Slobdchikoff 1988; 
Slobdichikoff et al. 1988). Other reports have concluded that prairie 
dog density is positively correlated with an increase in grazing, which 
simulates the shortgrass environment preferred by prairie dogs 
(Fagerstone and Ramey 1996; Marsh 1984, Slobodchikoff et al.

[[Page 6246]]

1988). The petition did not present substantial scientific information 
that poor rangeland management is threatening the species.
    We are aware that a relationship exists between overgrazing, 
cheatgrass proliferation, and fire frequency and intensity. However, we 
have no information in our files that addresses any correlation between 
fire and Gunnison's prairie dog populations. The petition does not 
present substantial scientific information that fire is threatening the 
Gunnison Prairie Dog.
    We have no information in our files that indicates that the 
transfer of public lands (privatization) has any significant influence 
on Gunnison's prairie dog populations and the petition does not present 
substantial scientific information that privatization is threatening 
the Gunnison Prairie Dog.
    We acknowledge that there are numerous land parcels within the 
Gunnison's prairie dog range that are leased for oil and gas 
development (Seglund et al. 2005). However, no information is available 
that quantifies the amount of occupied habitat that is affected. 
Menkens and Anderson (1985) concluded in a study of white-tailed 
prairie dogs that any impact from seismic testing is negligible. The 
petition does not present substantial scientific information that oil 
and gas development is threatening the Gunnison Prairie Dog.
    We acknowledge that roads are related to some Gunnison's prairie 
dog mortality. However, there is no information that indicates range-
wide impacts to the species from this factor and the petition does not 
provide substantial scientific information to support this assertion.
    We have significant information available in our files indicating 
that generally smaller, more isolated populations are more vulnerable 
to extirpation. In addition, isolation of colonies may also reduce the 
chance of recolonization after extirpation (Wagner and Drickamer 2002). 
The literature on prairie dogs and the effects of isolation is 
inconclusive. Lomolino et al. (2003) found that persistence of black-
tailed prairie dog towns increased significantly with larger town size 
and decreased isolation. However, Lomolino et al. (2003) and other 
recent reports (Cully and Williams 2001; Miller et al. 1993; Roach et 
al. 2001; Vosburgh 1996) also indicate that isolation and fragmentation 
may provide some protection to prairie dogs from sylvatic plague by 
lessening the likelihood of disease transmission. Conversely, large 
intercolony distances may not protect towns if agents of plague 
transmission include highly mobile species such as coyotes and raptors 
(Barnes 1982, 1993). Because we do understand the mechanics of plague 
transmission well, we are unable to find that isolation and 
fragmentation is wholly detrimental to the species as it may contribute 
to avoidance of plague transmission. The petition does not provide 
substantial scientific information to support an assertion that small 
colony size in and of itself in the absence of disease is currently 
threatening the Gunnison prairie dog.
Summary of Factor A
    We have determined that information in the petition and readily 
available in our files does not constitute substantial scientific 
information that any present or threatened destruction, modification, 
or curtailment of habitat is a threat to Gunnison's prairie dog such 
that listing under the Act may be warranted. However, more information 
on the impacts of fragmentation and isolation with regard to 
persistence of prairie dog populations is needed.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

Information Provided in the Petition
    The petition asserts that recreational shooting of Gunnison's 
prairie dogs threatens the species through population reduction, 
alteration of behavior, and potential extirpation of entire colonies. 
Citations are provided regarding the impact of shooting on prairie 
dogs, particularly black-tailed prairie dogs.
Evaluation of Information in the Petition
    We are aware that recreational shooting can reduce prairie dog 
population density at specific sites (Cully 1986; Knowles 2002; Miller 
et al. 1993; Vosburgh 1996; Vosburgh and Irby 1998; Wagner 2002; Wagner 
and Drickamer 2002), and acknowledge the possibility that local 
extirpation may have occurred in isolated circumstances (Knowles 1988). 
However, no information is available in the petition or our files to 
support a correlation between a range-wide decline of Gunnison's 
prairie dogs and recreational shooting. Prairie dog colonies typically 
experience increased population growth rates following shooting and can 
recover from very low numbers (Knowles 1988; Reeve and Vosburgh, In 
Summary of Factor B
    We have determined that information in the petition and readily 
available in our files does not constitute substantial scientific 
information that overutilization is a threat to Gunnison's prairie dog 
such that listing under the Act may be warranted.

C. Disease or Predation

Information Provided in the Petition
    The petition asserts that sylvatic plague threatens the Gunnison's 
prairie dog. The petition cites sources that report that plague is a 
non-native disease that was first reported in the species in 1932. It 
further cites sources that report that the species has almost a total 
lack of natural immunity, with mortality rates at infected colonies 
typically reaching 99 to 100 percent. The petition states that plague 
occurs throughout the range of the species and cites reports of 
epizootics in each of the states within the species' range. Some of the 
more significant epizootics cited by the petition include: The Dilkon 
region and Seligman region in Arizona; Saguache County and the South 
Park region in Colorado; Catron County and Moreno Valley in New Mexico; 
and Lisbon Valley and Tank Mesa in Utah.
    The petition describes declines in black-tailed prairie dog 
populations at Rocky Mountain Arsenal National Wildlife Refuge due to 
sylvatic plague. Following a plague epizootic in 1988, prairie dog 
populations declined by at least 90 percent. During the next few years, 
populations rebounded to approximately half of the original number 
before experiencing another epizootic. After the epizootic, populations 
again declined by at least 90 percent. This pattern has repeated itself 
at this site through three epizootics. Each time the maximum population 
attained has only been approximately half of the previous maximum 
population. The petitioner asserts that a similar pattern of decline is 
likely for Gunnison's prairie dog colonies exposed to plague.
Evaluation of Information in the Petition
    Information in our files supports the assertions made in the 
petition regarding sylvatic plague (Barnes 1982; Barnes 1993; Biggins 
and Kosoy 2001; Center for Disease Control 1998; Cully 1989; Eskey and 
Hass 1940; Gage and Kosoy 2005; Girard et al. 2004; Kartman et al. 
1966; Navajo Natural Heritage Program 1996; Olsen 1981; Seglund et al. 
2005; Stapp et al. 2004; Witmer 2004). Quantitative data indicate that 
plague has caused population declines in recent years at many well-
studied sites throughout the range of Gunnison's prairie dog (Cully 
1986; Cully 1989; Cully 1997; Cully et al. 1997; Ecke and Johnson 1952; 
Fitzgerald 1970; Fitzgerald 1993; Fitzgerald and

[[Page 6247]]

Lechleitner 1974; Girard et al. 2004; Kartman et al. 1962; Lechleitner 
et al. 1962; Lechleitner et al. 1968; Rayor 1985; Turner 2001; Wagner 
2002; Wagner and Drickamer 2002). All of the declines noted in Tables 2 
and 3 are due to plague epizootics. However, range-wide population 
trends may or may not follow this pattern (Table 1). Beyond absolute 
numbers, an additional consideration when evaluating Gunnison's prairie 
dog populations is the temporal fluctuation of occupied versus 
unoccupied habitat caused by periodic plague epizootics. We are unaware 
of any information at the landscape level that definitively suggests 
range-wide population declines caused by plague, although some reports 
indicate significant amounts of recently unoccupied habitat (Skiba, in 
litt. 2005 and Utah Division of Wildlife Resources, in litt. 2005), and 
many specific sites have experienced at least temporary reductions to 
extirpation or near extirpation (Tables 2 and 3).
    Plague is an exotic disease foreign to the evolutionary history of 
North American species (Barnes 1982; Barnes 1993; Biggins and Kosoy 
2001). Plague was first detected in Gunnison's prairie dogs in the 
1930s (Eskey and Hass 1940) and has subsequently spread throughout the 
range of the species (Center for Disease Control 1998; Cully 1989; 
Girard et al. 2004). Therefore, it has been present within the species' 
range for only approximately 70 years, allowing very little time for 
any resistance to evolve (Biggins and Kosoy 2001). Once established in 
an area, plague becomes persistent and periodically erupts, with the 
potential to eventually extirpate or nearly extirpate entire colonies 
(Barnes 1982; Barnes 1993; Cully 1989; Cully 1993; Cully et al. 1997; 
Fitzgerald 1993).
    Studies indicate that Gunnison's prairie dog populations are more 
susceptible to decline from sylvatic plague than white-tailed prairie 
dog populations, and are at least as, if not more, susceptible than 
black-tailed prairie dog populations (Antolin et al. 2002; Cully 1989; 
Cully and Williams 2001; Hubbard and Schmitt 1984; Knowles 2002; 
Ruffner 1980; Torres 1973; Turner 2001). Gunnison's prairie dogs 
commonly forage outside of their home territory, a characteristic that 
may play a significant role in the susceptibility of the species to 
plague. The Gunnison's prairie dog may be more susceptible to plague 
than the black-tailed prairie dog because of the Gunnison's less 
exclusive territorial behavior, where relatively many prairie dogs mix 
relatively freely throughout adjacent territories and thereby 
contribute to the communicability of plague. Additionally, plague is 
only present throughout approximately 66 percent of the black-tailed 
prairie dog's range (US Fish and Wildlife Service 2000) in comparison 
to 100 percent of the Gunnison's prairie dog's range (Center for 
Disease Control 1998; Cully 1989, Girard et al. 2004). The Gunnison's 
prairie dog is likely more susceptible to plague than the white-tailed 
prairie dog because the Gunnison's typically occurs at higher densities 
and is less widely dispersed on the landscape, allowing for more 
frequent transmission of the disease from one individual to another 
(Antolin et al. 2002, Cully 1989; Cully and Williams 2001; Turner 
    Many populations of Gunnison's prairie dogs have never been 
studied, and for those we have no information on their current 
population status or recent trends. In addition, for some previously 
studied sites we have no recent information regarding the status of the 
population. Tables 2 and 3 note declines due to plague at numerous 
sites throughout the range of the species For example, occupied habitat 
in South Park, Colorado was estimated at 915,000 ac (371,000 ha) in 
1945, 74,000 ac (30,000 ha) in 1948, and 42 ac (17 ha) in 2002. This 
decline was largely due to plague and affected a substantial portion of 
the species' extant occupied habitat in Colorado (at least 15 percent). 
Partial or complete recovery following population reductions due to 
plague has been reported at various sites for both white-tailed and 
black-tailed prairie dogs (Biggins and Kosoy 2001). In the few sites 
where Gunnison's prairie dog populations have been monitored after 
plague, only one population may have increased after the plague 
outbreak, but it is a very small fraction of pre-plague abundance.
Summary of Factor C
    We have determined that information in the petition and readily 
available in our files does not constitute substantial scientific 
information that disease or predation are threats to Gunnison's prairie 
dog such that listing under the Act may be warranted. We recognize that 
sylvatic plague has been and continues to be the major mortality factor 
for Gunnison's prairie dog at specific sites, but the impact that this 
disease has had on the overall status of the species, even at the State 
level, remains unclear. More information on the impacts of disease, 
specifically sylvatic plague, with regard to persistence of Gunnison's 
prairie dog populations is needed.

D. Inadequacy of Existing Regulatory Mechanisms

Information Provided in the Petition
    The petition documents the State and federal regulatory status of 
the Gunnison's prairie dog and asserts that those regulations are 
inadequate and constitute a threat to the species. Most concerns relate 
to a lack of restrictions with regard to chemical control and 
recreational shooting. However, information in our files indicates most 
of the Western Association of Fish and Wildlife Agencies (WAFWA) states 
have already established shooting restrictions on prairie dogs via 
state hunting regulations, however such regulations do not apply to 
tribal lands. The petition notes that in Arizona and Utah there is only 
a seasonal closure on public lands; and in Colorado and New Mexico, 
there is no season. The petition also notes that none of the state 
management plans developed in response to a petition on the black-
tailed prairie dog include any conservation measures for Gunnison's 
prairie dogs. The petition further claims that federal policies of 
various agencies and departments allow chemical control of the species.
Evaluation of Information in the Petition
    The current regulatory status with regard to Gunnison's prairie 
dogs is well documented in various State and federal statutes. However, 
the impacts resulting from these regulations or lack thereof are 
difficult to quantify. The petition notes that none of the State 
management plans developed in response to a petition on the black-
tailed prairie dog (Colorado Division of Wildlife 2003; New Mexico 
Black-tailed Prairie Dog Working Group 2001; Van Pelt 1999) include any 
conservation measures for Gunnison's prairie dogs. However, this would 
be expected since these plans address a different species and/or 
habitat type. All four States discuss the Gunnison's prairie dog in 
their Comprehensive Wildlife Conservation Strategies (Seglund et al. 
2005), and found the species deserving of special management 
    WAFWA has completed a conservation assessment for the species 
(Seglund et al. 2005) that describes regulatory status, occupied 
habitat estimates, limiting factors, and conservation needs for the 
species. After consideration of the contents of the assessment, the 
WAFWA and its Prairie Dog Conservation Team and White-tailed and 
Gunnison's Prairie Dog Working Group concluded that just active 
management and development of a comprehensive conservation strategy

[[Page 6248]]

for the species and its habitat are needed to conserve the species. 
Conservation planning efforts are underway among state and federal 
agencies for the Gunnison prairie dog with a strategy due to be 
completed by 2006.
    The range-wide assessment indicates that BLM has incorporated 
Gunnison prairie dog conservation into most land use plans.
Summary of Factor D
    Gaps in the regulatory mechanisms applicable to threats discussed 
in the analysis of the five factors are not determinative, as we do not 
have substantial scientific information that the species may warrant 
listing due to any of these potential threats, either together or in 

E. Other Natural or Manmade Factors Affecting the Species' Continued 

Information Provided in the Petition
    The petition cites sources that document early chemical control 
(poisoning) efforts directed toward the Gunnison's prairie dog. These 
early efforts were generally broad-scale and federally directed. 
Competition with livestock for forage was the most common impetus for 
chemical control of prairie dogs. The petition cites sources that 
report that in Arizona, a minimum of 2.3 million ac (935,000 ha) of 
Gunnison's prairie dog occupied habitat were poisoned from 1915-1964. 
In Colorado, New Mexico, and Utah, the petition notes that control 
efforts were not quantified by species. However, for all prairie dog 
species from 1915 to 1964, the petition cites sources that report 23.2 
million ac (9.4 million ha) poisoned in Colorado, 20.5 million ac (8.3 
million ha) poisoned in New Mexico, and 2.7 million ac (1.1 million ha) 
poisoned in Utah.
    The petition asserts that drought may have affected Gunnison's 
prairie dogs. It acknowledges that the effects of drought on the 
species have not been examined in the published scientific literature, 
but speculates that chemical control may be more likely during periods 
of drought.
Evaluation of Information in the Petition
    Information in our files supports the assertions made in the 
petition regarding dramatic declines in Gunnison's prairie dog occupied 
habitat associated with early chemical control efforts (Bailey 1932; 
Bell 1921; Ecke and Johnson 1952; Hubbard and Schmitt 1984; Forrest 
2002; Knowles 2002; Longhurst 1944; Oakes 2000; Seglund et al. 2005; 
Shriver 1965; Wagner 2002). In the early 1900s, strychnine treated 
grain was primarily used. In 1947, strychnine began to be replaced with 
compound 1080, which was used until it was rescinded in 1972 by 
Presidential Executive Order No. 11643 (Hubbard and Schmitt 1984). 
Since 1972, zinc phosphide has most often been used. Fewer chemical 
control efforts for the species have been federally directed in recent 
years and we are not aware of any recent large-scale chemical control 
programs. Consequently, the extent of impacts to the species likely has 
not continued to the same degree as in earlier years. We have no 
information to indicate that large scale poisoning is ongoing on the 
federal land management agencies. Information provided by the BLM 
indicates that no authorized poisoning is occurring on BLM lands. Other 
than a recitation of the effects of early chemical control activities, 
the petition does not provide substantial scientific information that 
chemical control is a current threat to the species, nor do we have 
information in our files that supports such a conclusion.
    Drought may affect some Gunnison's prairie dog populations in some 
circumstances, but no information regarding a direct relationship 
between drought and range-wide populations is available.
Summary of Factor E
    Substantial information is not presented by the petition or 
available in our files to indicate that other natural or manmade 
factors, in particular chemical control and drought, currently threaten 
the Gunnison's prairie dog such that listing under the Act may be 
    We have reviewed the information presented in the petition, and 
have evaluated that information in relation to information readily 
available in our files. On the basis of our review, we find that the 
petition does not present substantial scientific information indicating 
that listing the Gunnison's prairie dog species may be warranted due to 
any of the five threat factors. As noted previously under our 
discussion of factor C, we recognize that sylvatic plague has been and 
continues to be the primary mortality factor for Gunnison's prairie 
dog, especially at specific sites, but the impact that this disease has 
had on the overall status of the species is unclear. More information 
on the impacts of disease, specifically sylvatic plague, and on 
population status and trends is needed. The Service had already engaged 
the States in an effort to collect status information on the species, 
especially in areas where the current status of Gunnison's prairie dog 
in not well known. Results from these cooperative efforts should be 
available within a year. Once those results are available we will 
reevaluate the status of Gunnison's prairie dog.
References Cited
    A complete list of all references cited herein is available upon 
request from the Field supervisor (see ADDRESSES section).
    The primary authors of this document are staff at the South Dakota 
Ecological Services Office (see ADDRESSES section).

    Authority: The authority for this action is the Endangered 
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: January 30, 2006.
Marshall P. Jones, Jr.,
Acting Director, U.S. Fish and Wildlife Service.
[FR Doc. E6-1630 Filed 2-6-06; 8:45 am]