Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition to List the Wyoming Pocket Gopher as Endangered or Threatened with Critical Habitat, 19592-19607 [2010-8578]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 75, Number 72 (Thursday, April 15, 2010)]
[Proposed Rules]
[Pages 19592-19607]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-8578]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R6-ES-2008-0127]
[MO 92210-0-0008-B2]


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition to List the Wyoming Pocket Gopher as Endangered or 
Threatened with Critical Habitat

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding on a petition to list the Wyoming pocket gopher 
(Thomomys clusius) as endangered or threatened and to designate 
critical habitat under the Endangered Species Act of 1973, as amended. 
After review of all available scientific and commercial information, we 
find that listing the Wyoming pocket gopher as either endangered or 
threatened is not warranted at this time. We ask the public to continue 
to submit to us any new information that becomes available concerning 
the status of, or threats to, the Wyoming pocket gopher or its habitat.

DATES: The finding announced in this document was made on April 15, 
2010.

ADDRESSES: This finding is available on the Internet at https://www.regulations.gov at Docket Number FWS-R6-ES-2008-0127. Supporting 
documentation we used in preparing this finding is available for public 
inspection, by appointment, during normal business hours at the U.S. 
Fish and Wildlife Service, Wyoming Ecological Services Field Office, 
5353 Yellowstone Road, Cheyenne, WY 82009. Please submit any new 
information, materials, comments, or questions concerning this finding 
to the above street address.

FOR FURTHER INFORMATION CONTACT: Brian Kelly, Field Supervisor, Wyoming

[[Page 19593]]

Ecological Services Field Office (see ADDRESSES); by telephone at 307-
772-2374; or by facsimile at 307-772-2358. If you use a 
telecommunications device for the deaf (TDD), call the Federal 
Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Background

    Section 4(b)(3)(B) of the Endangered Species Act of 1973, as 
amended (Act) (16 U.S.C. 1531 et seq.) requires that, for any petition 
to revise the Federal Lists of Endangered and Threatened Wildlife and 
Plants that presents substantial scientific or commercial information 
indicating that listing the species may be warranted, we make a finding 
within 12 months of the date of the receipt of the petition. In this 
12-month finding, we may determine that the petitioned action is: (1) 
Not warranted, (2) warranted, or (3) warranted, but the immediate 
proposal of a regulation implementing the petitioned action is 
precluded by other pending proposals to determine whether species are 
endangered or threatened, and expeditious progress is being made to add 
or remove qualified species from the Federal Lists of Endangered and 
Threatened Wildlife and Plants. Section 4(b)(3)(C) of the Act requires 
that we treat a petition for which the requested action is found to be 
warranted but precluded as though resubmitted on the date of such 
finding, that is, requiring a subsequent finding to be made within 12 
months. We must publish these 12-month findings in the Federal 
Register.

Previous Federal Actions

    On August 9, 2007, we received a petition, dated August 7, 2007, 
from the Biodiversity Conservation Alliance and Center for Native 
Ecosystems requesting that we list the Wyoming pocket gopher (Thomomys 
clusius) within its known historic range, as threatened or endangered 
under the Act. Additionally, the petition requested that we designate 
critical habitat concurrent with listing. We acknowledged receipt of 
the petition in a letter dated September 6, 2007. In that letter, we 
advised the petitioners that we could not address their petition at 
that time because responding to existing court orders and settlement 
agreements for other listing actions required nearly all of our listing 
funding. We also concluded in that September 6, 2007, letter that 
emergency listing of the Wyoming pocket gopher was not warranted.
    On July 11, 2008, we informed the petitioners that, due to progress 
on addressing other priority listing actions, funding had become 
available to allow us to address the petition in fiscal year 2008. On 
November 4, 2008, the petitioners filed a complaint with the U.S. 
District Court for the District of Colorado against us for failing to 
complete the 90-day finding (Center for Native Ecosystems and 
Biodiversity Conservation Alliance v. U.S. Fish and Wildlife Service 
and Kempthorne (1:08-cv-02394-JLK)).
    On February 10, 2009, we published our finding that the petition to 
list the Wyoming pocket gopher presented substantial scientific or 
commercial information indicating that listing the species may be 
warranted (74 FR 6558). On March 20, 2009, the petitioners provided a 
notice of intent to sue on additional grounds for failure to complete 
the 12-month finding within 12 months of the petition. In a June 12, 
2009, stipulated settlement, the Service agreed to complete the 12-
month finding by April 10, 2010, which would allow us to include 2009 
Wyoming pocket gopher survey data in our analysis. This notice 
constitutes our 12-month finding on the August 7, 2007, petition to 
list the Wyoming pocket gopher as endangered or threatened.

Species Information

Life History
    Pocket gophers are powerfully built mammals, characterized by a 
heavily muscled head without a noticeable neck, strong front limbs with 
long nails used for digging, small ears, small eyes, and fur-lined 
cheek pouches used to carry food (Verts and Carraway 1999, p. 3). They 
are highly fossorial (adapted to burrowing or digging), living, 
foraging, and reproducing in burrow systems and underground tunnels 
that provide protection from predators and from extreme environmental 
conditions (Clark and Stromberg 1987, p. 121).
    Populations of pocket gophers generally tend to be small and 
patchily distributed across landscapes where they occur (Kennerly 1959, 
p. 251; Stinson 2005, p. 21). This distribution is thought to be 
primarily determined by the availability of soils appropriate for 
digging and foraging (Kennerly 1959, p. 249; Verts and Carraway 1999, 
p. 5). Specialization to local ecological conditions has resulted in a 
high degree of morphological variation across the range of each species 
(Patton and Brylski 1987, p. 493). For example, pocket gopher coat 
color is highly variable, strongly correlated with soil color, and 
thought to be an adaptive response to predation (Ingles 1950, p. 357; 
Wlasiuk and Nachman 2007, p. 567). Differences in abundance and 
nutritional content of forage can produce extreme variation in body 
size of individual pocket gophers and density of pocket gopher 
populations (Patton and Brylski 1987, p. 504).
    Little is known about the Wyoming pocket gopher; assumptions about 
its distribution, ecology, and status are based on a few museum 
records, reports from more than 30 years ago, and research conducted in 
2008 and 2009. This lack of knowledge has led to the recent efforts to 
obtain information on its distribution, status, and habitat use 
(Keinath and Griscom 2008, p. 1; Griscom et al. 2010, p. 3). Where 
specific life-history information is lacking, and where appropriate, we 
have provided information from other pocket gopher species, mainly in 
the Thomomys genus.
    The Wyoming pocket gopher is differentiated from other pocket 
gophers in its geographical range by being smaller and paler, with a 
yellow cast to the coat, especially in younger animals. The dorsal coat 
is uniform in color, and the margins of the ears are fringed with 
whitish hairs (Thaeler and Hinesley 1979, p. 483; Clark and Stromberg 
1987, p. 123; Keinath and Beauvais 2006, p. 8; Keinath and Griscom 
2008, p. 2). This species does not display sexual dimorphism 
(differences in form between the sexes) (Clark and Stromberg 1987, p. 
123; Keinath and Beauvais 2006, p. 8). Adult Wyoming pocket gophers 
typically have a body length of 112-134 millimeters (mm) (4.41-5.28 
inches (in)), hind foot length of 20-22 mm (0.79-0.87 in), and a weight 
of 44-72 grams (g) (1.54-2.54 ounces (oz)) (Thaeler and Hinesley 1979, 
pp. 483-484; Clark and Stromberg 1987, p. 123). The measurements of 
specimens captured in 2008 and 2009 included body lengths of 86-128 mm 
(3.38-5.04 in), hind foot lengths of 15-23 mm (0.59-0.91 in), and 
weights of 43-66 g (1.52-2.33 oz) (Griscom et al. 2010, p. 23). These 
somewhat smaller measurements for 2008-2009 data can be partly 
explained by late summer captures that included juveniles, whereas 
older studies relied on captures prior to June 15 that would have 
included only adults (Griscom 2010a, pers. comm.).
    The Wyoming pocket gopher occurs entirely within the range of the 
northern pocket gopher (Thomomys talpoides), but the two species likely 
occupy different habitats locally (Thaeler and Hinesley 1979, p. 486; 
Keinath and Beauvais 2006, p. 8; Griscom et al. 2010, p. 15). 
Approximately 50 percent of the known range of the species occurs on 
Bureau of Land Management (BLM) lands (Service 2009a, p. 1). A Wyoming 
Natural Diversity Database (WYNDD) predictive distribution model for 
the

[[Page 19594]]

Wyoming pocket gopher developed in January 2010 shows the species could 
occur in Sweetwater, Carbon, and Fremont Counties in Wyoming (Griscom 
et al. 2010, p. 32). The predicted range abuts Colorado's northern 
border, but Colorado was not included in the distribution analysis 
(Griscom et al. 2010, p. 32). Additional specimens are considered 
unlikely to be found south of current distribution points (Griscom et 
al. 2010, p. 12). To date, Wyoming pocket gophers have been located 
only in Sweetwater and Carbon Counties, which is consistent with 
historical records that show this area to be the extent of the species' 
range. Although the full historic range of the species has not been 
defined, we consider the capture points in Sweetwater and Carbon 
Counties presented by Thaeler and Hinesley (1979, pp. 482, 486-487) to 
present an approximation of historic range. This historic range 
includes the type specimen collected in 1857, two specimens collected 
in 1949 and 1951, and several specimens collected in the 1960s and 
1970s (Thaeler and Hinesley 1979, p. 487). Very little information 
exists regarding the actual population size of the Wyoming pocket 
gopher (Keinath and Beauvais 2006, p. 21). The only population estimate 
we found was 10,000 (NatureServe 2009, unpaginated). However, we are 
unable to determine the basis for this estimate and thus have no way to 
determine its scientific validity.
    Vegetation composition of a site may be more important in 
determining habitat for the Wyoming pocket gopher than soils or 
topography (Keinath and Griscom 2008, p. 2). The Wyoming pocket gopher 
occurs primarily in small ``islands'' of low vegetation within a 
sagebrush matrix. This matrix typically includes Artemesia tridentada 
wyomingensis (Wyoming big sagebrush), Chrysothamnus spp. (rabbitbrush), 
and other low shrubs, cushion plants, grasses, and forbs (Keinath and 
Griscom 2009, p. 1). In comparison to unoccupied control sites and 
northern pocket gopher capture sites, the Wyoming pocket gopher appears 
to prefer areas within this matrix with less perennial grass cover, 
less Artemesia tridentata (Big sagebrush), more Krascheninnikovia 
lanata (winterfat), more Atriplex gardneri (Gardner saltbush), more 
bare soil, less litter, and fewer surface rocks (Griscom et al. 2010, 
p. 15). Difference in habitat use would be expected, given that 
phenotype (observable physical characteristics) has been shown to 
correlate with habitat for pocket gophers (Ingles 1950, p. 357; Wlasiuk 
and Nachman 2007, p. 567).
    Previously, the Wyoming pocket gopher was believed to exclusively 
occupy well-drained, gravelly ridges instead of the valley bottoms and 
riparian areas with deeper soils preferred by the northern pocket 
gopher (Thaeler and Hinesley 1979, p. 486). However, recent research 
showed Wyoming pocket gophers occupy sites with more varied topography 
(Keinath and Griscom 2008, p. 2). Compared to northern pocket gophers, 
Wyoming pocket gophers appear to prefer areas of lesser slopes (Griscom 
et al. 2010, p. 15). Wyoming pocket gophers appear to use a variety of 
soil types that can be more compacted than those used by northern 
pocket gophers (Griscom et al. 2010, p. 15). These soils often have a 
substantial gravel component, usually contain little clay (Keinath and 
Griscom 2008, p. 2), and tend to be more alkaline than the soils that 
northern pocket gophers prefer (Griscom 2009a, pers. comm.). In 
general, pocket gophers in the Thomomys genus are more specialized for 
tooth digging rather than claw digging, which allows for exploitation 
of a broader range of soil types (Lessa and Thaeler 1989, p. 696). 
Based on the characterization of the Wyoming pocket gopher's size and 
habitat, it appears to fit the island model of isolation displayed by 
other species of pocket gophers specifically adapted to the soils of an 
area (Miller 1964, pp. 259-260). The limited distribution of the 
Wyoming pocket gopher relative to other species of pocket gopher may be 
due to its specialized habitat requirements (Keinath and Beauvais 2006, 
pp. 12-15).
    Pocket gophers construct extensive burrow systems. These systems 
consist of a main tunnel with side branches of shallow feeding tunnels 
(tunnels dug to forage on plant material). Additional feeding tunnels 
can be constructed when plant production is poor (Davis 1938, p. 338; 
Reichman et al. 1982, p. 691). The main tunnel also connects to a 
smaller system of chambers that serve as nest sites, food caches, and 
latrines (Miller 1964, p. 257; Keinath and Beauvais 2006, p. 16). 
Depths of the burrows vary from 6 to 12 inches below the ground 
surface. All aboveground entrances are plugged with soil (Clark and 
Stromberg 1987, p. 121). Burrow widths of the Wyoming pocket gopher are 
significantly smaller than those of the northern pocket gopher, likely 
reflecting their smaller body size (Griscom et al. 2010, p. 15). The 
extent of burrow systems can vary with the size of the individual, soil 
type, and plant production. The extensive tunneling and feeding 
activity of pocket gophers can have strong effects on soil formation, 
hydrology, nutrient flows, plant diversity, and competitive 
interactions of plants (Tilman 1983, pp. 290-292; Huntly and Inouye 
1988, entire; Reichman and Seabloom 2002, entire; Sherrod et al. 2005, 
pp. 586-587; Kyle et al. 2008, p. 377). The effects of pocket gopher 
burrowing on physical and chemical soil properties vary based on the 
nature of the soil (Kerley et al. 2004, pp. 164-165).
    The diet of pocket gophers consists of roots, stems, and leaves of 
forbs, with some consumption of grasses and shrubs (Aldous 1951, pp. 
85-86; Ward and Keith 1962, p. 747). The average consumption of forbs 
by pocket gophers in west-central Colorado, as measured by stomach 
content, was highest in July and August at 96 percent, decreasing to 73 
percent in October (Ward and Keith 1962, p. 747). Consumption of shrubs 
and roots of all types increased in late September and October, and 
consumption of grasses increased in June, September, and October (Ward 
and Keith 1962, p. 747). Pocket gophers in the Thomomys genus 
throughout the western United States generally prefer forb shoots 
during the growing season, and grass shoots, corms, and roots during 
periods of plant dormancy (Hunt 1992, pp. 47-48). Other species of the 
Thomomys genus (e.g., northern pocket gopher, Botta's (valley) pocket 
gopher (T. bottae), Townsend's pocket gopher (T. townsendii), Mazama 
(western) pocket gopher (T. mazama), and Camas pocket gopher (T. 
bulbivorus)) are not strict herbivores, in that they also seasonally 
consume the fungi associated with plant roots (i.e., are mycophagous) 
(Maser et al. 1978, p. 805; Taylor et al. 2009, p. 367). Pocket gophers 
may cut their food into small pieces and carry it in their cheek 
pouches back to the main burrow where it is consumed, stored for 
winter, used for nest building, or taken into tunnels and later pushed 
to the surface (Aldous 1951, p. 84; Verts and Carraway 1999, p. 6). 
Pocket gophers remain active all winter (Clark and Stromberg 1987, p. 
121).
    Based on the life histories of other pocket gophers, Wyoming pocket 
gophers presumably reproduce the calendar year following birth, have 
one litter with 4 to 6 young per year, and usually do not live more 
than two breeding seasons (Keinath and Beauvais 2006, p. 18). However, 
one northern pocket gopher is known to have survived for about 4 years 
(Hansen 1962, p. 153). Some species of pocket gophers have more than 
one litter per year in southern climates with longer breeding seasons 
(Miller 1946, pp. 335-336). Hansen (1960, p. 332) found no

[[Page 19595]]

evidence of more than one annual litter per female in the Rocky 
Mountain region.
    Pocket gophers are solitary animals and are typically found 
together only during the breeding season, or when females have young. 
Variation in levels of tolerance between males and females ranges from 
being together only during mating to raising young of the year together 
(Hansen and Miller 1959, pp. 581-582). Pocket gophers are usually 
polygynous (Reichman et al. 1982, p. 693). However, some evidence of 
serial monogamy has been found in Botta's pocket gopher in Arizona 
(Reichman et al. 1982, p. 693). The sex ratio for Botta's pocket gopher 
was one male per one female; however, the effective sex ratio was one 
male per two females as some small males did not reproduce (Reichman et 
al. 1982, p. 693). Populations of Botta's pocket gopher in California 
showed a much more skewed sex ratio, ranging from 1.4 to 4.67 females 
per male (Patton and Feder 1981, p. 917). We do not have specific 
information regarding the Wyoming pocket gopher mating system or sex 
ratio.
    Outside of the breeding season, pocket gophers are highly 
territorial, and males and females have exclusive territories. 
Generally, pocket gophers avoid each other (Reichman et al. 1982, p. 
693). The infrequent interactions that occur are mostly agonistic, 
occasionally escalating to open combat and even death (Zinnel and 
Tester 1994, p. 96). This aggression appears to have evolved as a means 
to ensure adequate individual food supplies, but could also be related 
to reproductive behaviors like mate guarding (Zinnel and Tester 1994, 
pp. 99-100). Pocket gopher population density is likely to be primarily 
regulated through intraspecific aggression; the number of animals an 
area can hold appears to be determined by combative interactions 
(Zinnel and Tester 1994, p. 100).
    Dispersal strategies of the Wyoming pocket gopher are unknown, but 
may be similar to other pocket gopher species. Although dispersal was 
common, 63 percent of individual Botta's pocket gophers set up their 
territory within 40 meters (m) (131.23 feet (ft)) of their natal home 
(Daly and Patton 1990, p. 1291). Average dispersal lengths for Botta's 
pocket gopher are estimated at 100-500 m (328.08-1,640.42 ft) per year 
(Hafner et al. 1998, p. 281). Individual Botta's pocket gophers that 
disperse are typically young, pre-reproductive, and more likely to be 
female (Daly and Patton 1990, p. 1287). Pre-reproductive juvenile 
females begin dispersing as early as the summer following their birth, 
while males typically delay dispersal for up to one year after birth 
(Daly and Patton 1990, p. 1287). Spring dispersal is common in 
reproductive adults of both sexes. Fifty percent of plains pocket 
gopher (Geomys bursarius) female adults relocate after raising a 
litter, leaving the site in possession of female young (Zinnel and 
Tester 1994, p. 99). Once pocket gophers establish territories and 
burrows, they may shift to other areas based on environmental 
conditions or interactions with other pocket gophers, but they 
generally do not move far from original territories (Miller 1964, p. 
262; Reichman et al. 1982, pp. 687-688; Daly and Patton 1990, p. 1286).
Taxonomy
    The Wyoming pocket gopher (Thomomys clusius) is a member of the 
Geomyidae (pocket gopher) family. Including the Wyoming pocket gopher, 
nine species are currently assigned to the genus Thomomys. The type 
specimen for Wyoming pocket gopher was collected in 1857 by Dr. W.A. 
Hammond near Rawlins, Wyoming, but was not described and given the name 
Thomomys clusius until 18 years later (Coues 1875, p. 138). The 
designation of the Wyoming pocket gopher within Thomomys has changed 
over time, with the name clusius being applied at both the species and 
subspecies level to various pocket gopher specimens collected in 
southern Wyoming (Keinath and Beauvais 2006, p. 11).
    Thaeler and Hinesley (1979, entire) clarified the Wyoming pocket 
gopher taxonomy with karyotype (i.e., a count of the number of diploid 
chromosomes) and morphological analyses of pocket gopher specimens 
collected in Wyoming. Members of the pocket gopher genus Thomomys are 
the most karyotypically and morphologically diverse group of mammals 
known (Patton 1972, p. 574; Patton and Brylski 1987, p. 493). The 
Wyoming pocket gopher has a unique karyotype of 2n = 46, a yellowish 
coat, and a generally small size, which support the validity of Wyoming 
pocket gopher as a distinct species within Thomomys (Thaeler and 
Hinseley 1979, p. 483). These traits differed significantly from the 
northern pocket gopher, which occurs across the range of the Wyoming 
pocket gopher. Although northern pocket gophers are generally darker 
and larger, they share morphological similarities with Wyoming pocket 
gophers that had led to some misidentification of specimens in earlier 
publications (e.g., Bailey 1915 and Long 1965, cited in Keinath and 
Beauvais 2006, p. 11). Thus, karyotype analysis was previously thought 
necessary for positive identification. Northern pocket gophers differ 
from Wyoming pocket gophers in that they have a karyotype of 2n = 48 or 
56, depending on the subspecies (Thaeler and Hinesley 1979, p. 483). 
However, based on the amplified fragment length polymorphism (AFLP) 
analysis completed on tail clippings during the 2008 field season, 
field assessment of phenotype was shown to be a reasonably reliable 
method for discerning the two species from each other (Hayden-Wing 
Associates 2008, p. 3; Beauvais 2009, p. 1; McDonald 2009a, pers. 
comm.). AFLP testing showed strong genetic signals that clearly 
differentiate the Wyoming pocket gopher from other species of pocket 
gophers (Beauvais 2009, p. 1; McDonald 2009a, pers. comm.). This recent 
genetic analysis has confirmed definitively what taxonomists had 
determined historically: the Wyoming pocket gopher is a unique species 
representing a monophyletic clade (i.e., descended from one common 
ancestor) (McDonald 2009a, pers. comm.).

Summary of Information Pertaining to the Five Factors

    Section 4 of the Act, and its implementing regulations at 50 CFR 
424, set forth the procedures for adding species to, removing species 
from, or reclassifying species on the Federal Lists of Endangered and 
Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, a 
species may be determined to be endangered or threatened based on any 
of the following five factors: (A) The present or threatened 
destruction, modification, or curtailment of its habitat or range; (B) 
overutilization for commercial, recreational, scientific, or 
educational purposes; (C) disease or predation; (D) the inadequacy of 
existing regulatory mechanisms; or (E) other natural or manmade factors 
affecting its continued existence. Under section 4(b)(1)(A), this 
determination should be made on the basis of the best scientific and 
commercial data available and after conducting a status review and 
taking into consideration State conservation efforts. In making our 12-
month finding on a petition to list the Wyoming pocket gopher, we 
considered and evaluated the best available scientific and commercial 
information. Information pertaining to the status and threats to the 
Wyoming pocket gopher in relation to the five factors provided in 
section 4(a)(1) of the Act is discussed below.

[[Page 19596]]

Factor A. The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range

    Wyoming pocket gopher habitat is exposed to a number of influences 
that may affect the species, including energy exploration and 
development, road construction and use, climate change and drought, 
introduction of nonnative species, grazing, and urbanization. However, 
no studies have been conducted to determine the species' response to 
these influences, or to the potential changes in habitat that may 
result. Where information specific to the Wyoming pocket gopher is 
lacking, we have utilized information from other pocket gopher species, 
mainly in the Thomomys genus.
    Literature describes both positive and negative effects to other 
species of pocket gophers resulting from various types of disturbance. 
Many pocket gopher species exhibit a positive response of increased 
rates of mound-building activities when vegetation has been disturbed 
(Mielke 1977, p. 175). Three species (Botta's pocket gopher, plains 
pocket gopher, and yellow-faced pocket gopher (Cratogeomys castanops)) 
are more common in disturbed areas, such as roadways and floodplains, 
in New Mexico (Best 1973, p. 1314). Similarly, pocket gopher (Thomomys 
spp.) burrows were frequently observed along roadways in Nevada, but 
not the adjacent creosote habitats, suggesting they were using areas 
where the habitat would have been unsuitable without the disturbance 
(Garland and Bradley 1984, p. 54). In contrast, plains pocket gophers 
and yellow-faced pocket gophers in southwestern Kansas are not present 
within areas of intensive agricultural operations involving annual 
plowing or disking (Hoffman et al. 2007, p. 300). Intensive residential 
and commercial development has reduced patch sizes of Mazama pocket 
gopher habitat in western Washington such that the species no longer 
occurs in many areas (Service 2009b, pp. 7-8; Flotlin 2010, pers. 
comm.). The response to disturbance may be dependent on the species, as 
the plains pocket gopher is more common in disturbed areas, such as 
roadsides and cultivated fields, while the yellow-faced pocket gopher 
is more common in native shortgrass prairie in southeastern Colorado 
(Moulton et al. 1983, p. 58).
    In 2008 and 2009, WYNDD, with the assistance of several other 
groups, trapped Wyoming pocket gophers, northern pocket gophers, and 
Idaho pocket gophers (T. idahoensis) to better understand the species' 
range and distribution, habitat requirements and preferences, and the 
genetic and morphological differences between species (WYNDD 2009, p. 
2; Hayden-Wing Associates 2008, p. 1; Keinath and Griscom 2008, p. 1; 
Griscom et al. 2010, pp. 5-7). This effort resulted in the successful 
trapping of 31 confirmed Wyoming pocket gophers distributed across the 
species' currently known range (Griscom et al. 2010, p. 5; Griscom 
2010b, pers. comm.). Prior to 2008, a total of 16 confirmed Wyoming 
pocket gophers had been captured, and all of these confirmed specimens 
were collected by Charles Thaeler approximately 40 years ago (Griscom 
2009b, pers. comm). This information provided both historic and recent 
locations for our use in creating a general assessment of Wyoming 
pocket gopher presence to ascertain if the known locations of the 
species have changed over time. Based on the limited number of 
collection sites, the species appears to be currently distributed 
throughout its known range in a pattern that approximates historic 
distribution (Figure 1). Therefore, we find no evidence that 
curtailment of the species' range is occurring.

[[Page 19597]]

[GRAPHIC] [TIFF OMITTED] TP15AP10.000

    Figure 1: Historic and current capture locations of the Wyoming 
pocket gopher (Data compiled from Service, Bureau of Land Management, 
WYNDD, U.S. Geological Survey, U.S. Census Bureau, ESRI).
    Although there is no evidence of curtailment of the species' range, 
habitat of the Wyoming pocket gopher is exposed to various influences 
that may affect the species, including energy exploration and 
development, road construction and use, introduction of nonnative 
species, climate change, drought, grazing, and urbanization. These 
variables that may affect the species' habitat are discussed below.

Energy Exploration and Development

    The primary forms of existing and planned energy development in the 
range of the Wyoming pocket gopher are oil, gas, and wind. Based on 
existing

[[Page 19598]]

National Environmental Policy Act (NEPA) (42 U.S.C. 4321 et seq.) 
documents for major oil and gas developments, estimates of project life 
for major oil and gas developments within the Wyoming pocket gopher's 
range are between 10-50 years (Service 2010a, p. 3). Some non-renewable 
energy development is already occurring within the species' known 
occupied range. Renewable energy development is estimated to reach 
maximum development by 2030 (U.S. Department of Energy 2008, p. 10), 
and several developments are being considered within the species' 
range. Based on this information, we estimate the foreseeable future of 
energy development at a minimum of 10 years, but anticipate that energy 
development will be present for up to 50 years.
    WYNDD is analyzing potential threats to Wyoming's 152 species of 
greatest conservation need related to energy development in its 
Assessment of Wildlife Vulnerability to Energy Development (AWVED). 
Preliminary conclusions from the AWVED analysis indicate that the 
Wyoming pocket gopher is Wyoming's species with the highest potential 
risk for energy-related effects based on its proximity to existing 
wells, the proportion of lands leased for oil and gas within its range, 
and the density of wells within that range (Keinath 2009, pp. 12-13). 
This potential risk is based on exposure to energy development across 
the species' range and is not based on any known effects to the species 
from energy development activities. Our February 10, 2009, 90-day 
finding (74 FR 6558) acknowledged that the likelihood of oil and gas 
development throughout the species' range is high based on the energy 
development potential and existing leases that cover much of the range. 
Approximately 4,000 actively producing oil and gas wells are within the 
range of the species (Service 2010b, p. 3), and an additional 10,000 
oil and gas wells have been proposed in that area (Service 2010a, p. 
1). In this finding, rather than what was done in our previous 90-day 
finding on the petition, we are determining whether the best available 
information indicates that the species meets the definition of a 
threatened or endangered species and therefore warrants listing under 
the Act, which is a more in-depth analysis than the one conducted for 
the 90-day finding.
    Several different types of oil and gas exploration and development 
activities occur within the range of the Wyoming pocket gopher. Oil and 
gas geophysical exploration is conducted to generate a subsurface image 
of fluid minerals and usually involves either drilling holes and 
detonating explosives or using a vibrating pad that is driven across an 
area using heavy vehicles. The extent of impacts from either 
exploration method on pocket gophers is unknown. The vibrations and 
potential soil impacts would, at a minimum, temporarily alter habitat 
and may result in collapse of burrows. Pocket gophers in the immediate 
vicinity of operations would likely notice the activity, but the type 
of response is unknown. Pocket gopher communication likely occurs 
through seismic signals (Mason and Narins 2001, p. 1177), and frequent 
vibrations could disrupt signals used to attract mates, warn of 
intruders, or avoid predators. However, we have no information to 
support that energy exploration negatively impacts the species.
    Oil and gas development involves staging a drilling rig and setting 
up additional equipment that is used during production. Generally, 
developers build roads to access each site and clear and level well 
pads. These soil-disturbing activities would affect the habitat that 
lies within and adjacent to the footprint of well pads and roads. Any 
soil that is moved could have a direct impact on pocket gophers that 
are present. Once a rig is in place, the drilling process creates 
vibrations that could affect habitat and any pocket gophers in the 
area. Once a well has been drilled and is producing, energy companies 
make regular trips to well pads to monitor production, conduct 
maintenance, or collect extracted resources. These regular trips may 
disturb, either directly or through the resulting noise, pocket gophers 
that are present at or near well pads and roads. In the past, the 
Wyoming pocket gopher has been considered potentially vulnerable to 
disturbance because the reasons for the species' limited distribution 
had not yet been explained (Keinath and Beauvais 2006, p. 21). However, 
as described above, certain types of disturbance can elicit a positive 
population response in some pocket gopher species.
    Energy producers often try to maintain a clear work area by using 
herbicides on well pads and along roads. Herbicide use and the direct 
impacts of development would reduce the availability and quality of 
vegetation, creating negative effects to Wyoming pocket gopher habitat 
(Keith et al. 1959, pp. 142-144). In general, broadcast herbicide 
application is assumed to be minimal in southern Wyoming (Keinath and 
Beauvais 2006, p. 22). We do not have information on use of herbicides 
for oil and gas development, and we are unaware of monitoring for 
resulting vegetative shifts. Therefore, we are unable to assess how 
changes in the vegetation due to herbicide use may affect the Wyoming 
pocket gopher. The BLM does not use pesticides or rodenticides in 
Wyoming to protect reclamation areas (Abbott 2009a, pers. comm.), so we 
do not anticipate direct mortality from these substances in reclamation 
areas. Introduction and spread of nonnative plants may result from 
energy development activities, and the potential threat of nonnative 
vegetation to the Wyoming pocket gopher is discussed separately below.
    We used information from Wyoming pocket gopher trapping and from 
known oil and gas development to assess the extent to which energy 
development may be affecting the species. By overlaying producing wells 
on a map with species capture sites, we found that the locations of 
capture sites in relation to new and existing development does not 
appear to reflect a pattern of either species avoidance of, or 
preference for, producing oil and gas wells. Some capture sites are as 
near as 95 m (312 ft) to a producing well site (Service 2010b, p. 2), 
while others are in areas that have no oil or gas wells. We recognize 
that this simple geospatial assessment has limitations in determining 
what effects oil and gas development has on the species. We also 
recognize dispersal is likely already difficult across portions of the 
range that do not currently have pocket gophers, and recolonization 
following local extirpation would be unlikely (Keinath et al. 2008, p. 
7).
    The amount of surface disturbance provides another approach to 
consider the impacts of natural gas development. The two largest 
natural gas developments not yet fully built in the Wyoming pocket 
gopher range are Atlantic Rim and Continental Divide-Creston (Service 
2010a, p. 1). The scoping notice for the Continental-Divide Creston 
development states disturbances during initial development will be 
approximately 47,060 acres (ac) (19,045 hectares (ha)) of 1.1 million 
ac (445,154 ha), or 4.28 percent of the project area (BLM 2006a, p. 4). 
The impacted area will be reduced to 1.67 percent through interim 
reclamation (BLM 2006a, p. 4). As this proposal includes areas of 
infill, the amount of disturbance described in the scoping notice does 
not include existing development (BLM 2006a, p. 1). The proposed well 
density includes 8 wells per square mile, with a possibility of up to 
16 wells per square mile in certain areas (BLM 2006a, p. 1). The Record 
of Decision for the Atlantic Rim development allows a total surface

[[Page 19599]]

disturbance of 2.8 percent of the project area at a given time, with 
well spacing of 8 wells per square mile (BLM 2007, p. 10). For 
comparison, the existing Continental Divide/Wamsutter II gas 
development has been mostly developed, with 22,400 ac (9,065 ha) of 
surface disturbance across 1,061,200 ac (429,452 ha) (2.11 percent of 
the project area) and well densities of 1 to 8 wells per square mile 
(BLM 2000, section 2.0). All of these surface disturbance percentages 
are small. Although we do not know how the Wyoming pocket gopher is 
likely to respond to any proposed increases in well numbers, the level 
of development indicates that large interstitial spaces will continue 
to be available for Wyoming pocket gopher use. We know from our 
analysis that the Wyoming pocket gopher does occur near developed areas 
(Service 2010b, p. 2).
    The BLM administers approximately half of the lands within the 
Wyoming pocket gopher range (Service 2009a, p. 1). Throughout the 
range, the BLM has leased 41.23 percent of the Wyoming pocket gopher 
range for oil and gas development, and 11.23 percent of the range on 
BLM lands has producing oil and gas leases (Service 2010c, p. 2). We 
are unable to determine whether development will occur on all leases.
    Given limited knowledge of pocket gopher response to oil and gas 
development, and both the positive and negative observed impacts of 
disturbance to other species of pocket gophers, we do not consider 
producing wells at current or projected levels to be a threat to the 
Wyoming pocket gopher.
    Although little wind development has occurred within the range of 
the species, projections for future wind energy are significant. One 
major proposal, the Chokecherry and Sierra Madre Wind Energy Project, 
includes 1,000 wind turbines across 98,500 ac (39.66 ha) within the 
range of the Wyoming pocket gopher (AECOM 2009, p. 1). Wind development 
may cause effects to habitat that are similar to oil and gas 
development. Wind development also results in a network of pads 
connected by roads. Soils are disturbed during development, and 
frequent maintenance trips are necessary. The Wyoming pocket gopher's 
response to wind development within its habitat is not known. For the 
Botta's pocket gopher, researchers mapping prey base to better 
understand raptor mortalities at a wind farm in California observed 
that pocket gophers were clustered near the wind turbines (Thelander et 
al. 2003, p. 23). They attributed this to the pocket gophers' 
attraction to the vertical and lateral edges formed by access roads and 
the area around wind towers (Thelander et al. 2003, p. 24). We 
anticipate that the response of the Wyoming pocket gopher may be 
similar, but we lack species-specific information. Therefore, the best 
available information does not indicate whether current or future wind 
development will have positive or negative effects on the Wyoming 
pocket gopher.
Summary of Energy Exploration and Development
    Little information exists to indicate whether the Wyoming pocket 
gopher will be affected by an increased density of wells or by an 
expansion of oil, gas, and wind development into currently undeveloped 
areas. The response to disturbance in pocket gophers appears to be 
species-specific. For example, in southeastern Colorado, the plains 
pocket gopher is more common in disturbed areas, but the yellow-faced 
pocket gopher is more common in native versus disturbed habitats 
(Moulton et al. 1983, p. 58). Based on our current understanding of the 
Wyoming pocket gopher, energy development, at levels that we can detect 
or anticipate, is as likely to benefit Wyoming pocket gophers as it is 
to harm them.
    We have no information that additional energy development activity 
will fragment habitat in a way that will significantly limit dispersal, 
movement, or genetic interchange. Using the best available information, 
we conclude that these habitat alterations do not constitute a threat 
to the Wyoming pocket gopher now, or in the foreseeable future.

Road Construction and Use

    Roads are built to create access for oil, gas, and wind 
developments, as well as for other activities that occur on the 
landscape, including recreation, grazing, and land management. Much of 
the recent expansion of road networks in Wyoming pocket gopher habitat 
is related to energy development, but some areas have also likely 
experienced an increase in access by recreational vehicles. Expansion 
of road networks may fragment the species' habitat, create barriers to 
movement of the species, isolate individual populations, and increase 
opportunities for invasive species (Keinath and Beauvais 2006, pp. 22-
23). Roads may increase direct mortality from vehicles, but this source 
of mortality is not always significant to populations (Garland and 
Bradley 1984, p. 52). Roads also may improve habitat for pocket gophers 
in some ways by providing looser soil and increasing vegetation in 
rights-of-way from precipitation run-off. As described above, roads can 
have a positive effect on other pocket gopher species (Best 1973, p. 
1314; Moulton et al. 1983, p. 58; Garland and Bradley 1984, p. 54). The 
effects of roads on Wyoming pocket gopher populations are not known; 
however, we have limited anecdotal observations of individual gopher 
occupancy near roads. In 2009, one Wyoming pocket gopher specimen was 
captured 7 m (23 ft) from a graded dirt road, and northern pocket 
gophers were captured as close as 2 m (6.5 ft) to a graded dirt road 
(Griscom 2009b, pers. comm.). Small mammals may avoid roads due to 
noise and other factors, but roads may also provide additional habitat 
or movement corridors (Garland and Bradley 1984, entire; U.S. 
Department of Transportation 2009, unpaginated). Northern pocket 
gophers have been observed digging tunnels underneath a right-of-way 
road (Richens 1966, p. 532).
    Depending upon the size of the road and the associated degree of 
soil compaction, a road may impact the dispersal of Wyoming pocket 
gophers. For example, distribution of the Shelton pocket gopher (T. 
mazama couchi) was impacted by soil compaction around an airport 
runway, and no pocket gopher activity was observed in graded areas that 
appeared to be highly compacted (GeoEngineers 2003, p. 15). The Wyoming 
pocket gopher apparently can use more compacted soils than the northern 
pocket gopher (Griscom et al. 2010, p. 15), but we are unsure what 
amount of soil compaction would begin to limit habitat use by the 
Wyoming pocket gopher.
    Many roads in the range of the Wyoming pocket gopher have been on 
the landscape for decades or for more than a century, while others have 
been developed within the past few years. Evidence suggests some 
historic wagon trails (a type of road) have lasted for well over 100 
years (BLM 2009, unpaginated), even when use of the road is 
discontinued. Other roads are reclaimed and do not have such a lasting 
effect. We anticipate that the existing roads within the range of the 
Wyoming pocket gopher will persist for at least 10 to 50 years in 
support of energy development activities. Additional roads may also be 
constructed to support that development, while others are reclaimed 
when no longer necessary. We anticipate that county roads providing 
access to livestock management facilities, homes, and recreational 
opportunities will persist indefinitely.

[[Page 19600]]

    We conclude the effects of roads on the Wyoming pocket gopher may 
be positive and negative. Although we remain concerned about the 
potential impacts of roads, the best available information does not 
indicate that road construction and use poses a threat to the Wyoming 
pocket gopher now, or in the foreseeable future.

Nonnative Species

    The introduction of nonnative species may affect the Wyoming pocket 
gopher, but the degree of impact from these species is not clear. A 
review of Wyoming pocket gopher information resulted in no information 
indicating a likelihood that nonnative vegetation alters or restricts 
pocket gopher populations; nonnative species were viewed as a potential 
threat, but not a current threat (Keinath and Beauvais 2006, p. 23). We 
do not fully understand the extent to which nonnative species will 
spread throughout the species' range into the future. Nonnative 
vegetation is considered a threat to the Mazama pocket gopher in 
western Washington (Service 2009b, pp. 7-8). The Mazama pocket gopher 
is adapting to the presence of many types of nonnative vegetation; 
however, the presence of Cytisus scoparius (Scotch broom), which has 
large root masses, restricts pocket gopher dispersal. The loss of 
prairie habitat to conifer encroachment is also a threat to the Mazama 
pocket gopher (Flotlin 2010, pers. comm.). Cytisus scoparius does not 
occur within the range of the Wyoming pocket gopher, and conifer 
encroachment is limited.
    To inform our evaluation of the potential threat from nonnative 
species, we looked at the potential for Bromus tectorum (cheatgrass) to 
impact Wyoming pocket gopher populations. The conversion from A. 
tridentata spp. to B. tectorum has been shown to negatively impact 
other small mammals (Yensen et al. 1992, p. 309). The spread of B. 
tectorum has the potential to change vegetative communities in a way 
that could affect the Wyoming pocket gopher. As discussed previously, 
forbs are an important component of pocket gopher diets, and high 
densities of B. tectorum reduce the biomass and growth rates of forbs, 
as well as seedling survival for some forb species (Parkinson 2008, pp. 
37-46). Further, when chemical treatments were used to experimentally 
reduce the abundance of weedy forbs in favor of grasses, a northern 
pocket gopher population declined roughly in proportion to the loss of 
forbs (Keith et al. 1959, p. 231).
    Pocket gophers that eat grass species have reduced body weights 
(Tietjen et al. 1967, pp. 642-643). Grasses, when not consumed with 
other vegetation, do not seem to provide an adequate diet for Thomomys 
species (Cox 1989, p. 80). While Bromus tectorum may impact the 
abundance of forbs in the species' habitat, B. tectorum may also be 
used by Wyoming pocket gophers. Small quantities of the seeds of B. 
tectorum have been occasionally found in tunnels of northern pocket 
gophers, although seed heads of B. tectorum were not preferred as 
forage (Cox 1989, pp. 78-80). Northern pocket gophers also occur at 
locations where B. tectorum was considered to be a prevalent plant 
species (Ostrow et al. 2002, p. 992). During their breeding season, 
Botta's pocket gophers have been found to consume substantial 
quantities of species related to B. tectorum, B. mollis (soft brome) 
and B. rubens (red brome), when the nutrient content of the plants was 
highest (Hunt 1992, p. 49).
    While Bromus tectorum appears to have the potential to impact 
Wyoming pocket gopher habitat, the spread of B. tectorum throughout the 
habitat of the Wyoming pocket gopher is not a foregone conclusion. In 
Wyoming, B. tectorum can be locally abundant, but precipitation and 
elevation differences influence where B. tectorum occurs (Smith and 
Enloe 2006, p. 1). In southern Wyoming counties, the fall precipitation 
prior to cold weather needed for B. tectorum germination is generally 
rare in zones where 14 inches or less of precipitation is received 
annually (Smith and Enloe 2006, p. 1). The annual precipitation within 
the range of the Wyoming pocket gopher is generally less than 14 inches 
of precipitation annually (National Atlas 2005, unpaginated).
    In approximately the last 100 years, no broad-scale B. tectorum 
eradication method has been developed. Given the history of invasive 
plants on the landscape, the continued challenges in controlling such 
species, and the current infestation of invasive plants across the 
Wyoming pocket gopher's range, we anticipate that invasive plants will 
be on the landscape for the next 100 years or longer. However, studies 
indicate B. tectorum germination may be generally rare in Wyoming 
pocket gopher habitat, possibly inhibiting the future spread and impact 
of this invasive species in Wyoming pocket gopher habitat. In summary, 
we could find no information suggesting that nonnative species or B. 
tectorum, where it occurs within the occupied range of the Wyoming 
pocket gopher, represent a threat to the species now, or in the 
foreseeable future.

Climate Change

    The Intergovernmental Panel on Climate Change (IPCC) has concluded 
that warming of the climate is unequivocal and that continued 
greenhouse gas emissions at or above current rates will cause further 
warming (IPCC 2007, p. 30). Eleven of the 12 years from 1995 through 
2006 rank among the 12 warmest years in the instrumental record of 
global surface temperature since 1850 (Independent Scientific Advisory 
Board 2007, p. 6). Climate-change scenarios estimate that the mean air 
temperature could increase by more than 3 degrees Celsius (5.4 degrees 
Fahrenheit) by 2100 (IPCC 2007, p. 46). The IPCC also projects that 
there will very likely be regional increases in the frequency of hot 
extremes, heat waves, and heavy precipitation (IPCC 2007, p. 46), as 
well as increases in atmospheric carbon dioxide (IPCC 2007, p. 36).
    Plant species provide habitat and forage that affect the ability of 
mammal species, such as the Wyoming pocket gopher, to persist over 
time. A variety of plant-related factors are not included in climate 
space models, including the effect of elevated carbon dioxide on plant 
water-use efficiency, the physiological effect to the species of 
exceeding the assumed (modeled) bioclimatic limit, the life stage at 
which the limit affects the species (seedling versus adult), the life 
span of the species, and the movement of other organisms into the 
species' range (Shafer et al. 2001, p. 207). These factors would likely 
help determine how climate change would affect plant species 
distributions. While more empirical studies are needed on what 
determines species and multi-species distributions, those data are 
often lacking; in their absence, climatic space models can play an 
important role in characterizing the types of changes that may occur so 
that the potential impacts on natural systems can be assessed (Shafer 
et al. 2001, p. 213).
    One study modeled potential climate change impacts to A. tridentata 
spp., which are representative of the ecosystem currently known to be 
occupied Wyoming pocket gopher habitat (Shafer et al. 2001, pp. 200-
215). Each scenario in the study predicted a reduction in the size of 
the overall range of sagebrush and shift where sagebrush may occur. 
These simulated changes were the result of increases in the mean 
temperature of the coldest month, which the authors speculated may 
interact with soil moisture levels to produce the simulated impact. 
Each model predicted that climate suitability

[[Page 19601]]

for big sagebrush would shift north into Canada. Other areas within big 
sagebrush distributions would become less suitable climatically and 
would potentially cause a significant contraction in sagebrush range. 
Since the Wyoming pocket gopher is associated with sagebrush in the 
matrix that forms Wyoming pocket gopher habitat, contractions of 
sagebrush could result in negative effects to the species. However, 
although the Wyoming pocket gopher occurs within sagebrush habitats, 
the species prefers vegetation other than sagebrush at a finer scale 
within that matrix (Griscom et al. 2010, p. 15).
    In some cases, effects of climate change can be demonstrated (e.g., 
McLaughlin et al. 2002, p. 6073). Where it can be, we rely on that 
empirical evidence, such as increased stream temperatures (see Rio 
Grande cutthroat trout, 73 FR 27900, May 14, 2008) or loss of sea ice 
(see polar bear, 73 FR 28212, May 15, 2008), and treat it as a threat 
that can be analyzed. The degree to which climate change will interact 
with ecological processes important to Wyoming pocket gophers is not 
currently known.
    Based on the evolutionary and ecological response of pocket gopher 
species to past global warming and cooling events, changes in 
temperature and precipitation may result in phenotypic and density 
changes in Wyoming pocket gopher populations (Hadly 1997, p. 292; Hadly 
et al. 1998, p. 6896; Barnosky et al. 2003, pp. 360-361), but we have 
no information specific to the Wyoming pocket gopher. If the Wyoming 
pocket gopher's range experiences increased temperatures and reduced 
precipitation in the future, these changes could include reduced body 
size and population abundance (Hadly 1997, p. 292). Past climate-
induced, population-level, phenotypic change in pocket gophers was 
likely the result primarily of developmental plasticity within 
populations and not large-scale migration (Hadly et al. 1998, p. 6896; 
Barnosky et al. 2003, p. 362). Measured changes in phenotype and 
population size appeared to be an initial response to global warming 
episodes, with the extent of change being dependent upon the magnitude 
and duration of climatic change (Barnosky et al. 2003, pp. 364-365).
    Smaller body size and reduced abundance experienced by historical 
pocket gopher populations during global hot, dry periods is likely a 
response to reduced food availability during those periods (Hadly 1997, 
p. 290). Projected climate change has the potential to significantly 
alter the distribution of forage important to pocket gophers through 
shifts in timing and amount of precipitation, or through changes in 
seasonal high, low, or average temperatures (Bachelet et al. 2001, p. 
174). For example, warmer temperatures and greater concentrations of 
atmospheric carbon dioxide create conditions favorable to Bromus 
tectorum, which outcompetes native vegetation and greatly accelerates 
the natural fire cycle in areas where it becomes established (Chambers 
and Pellant 2008, p. 31; Global Climate Change Impacts in the United 
States 2009, p. 83). Future carbon dioxide emissions from energy use 
are projected to increase by 40 to 110 percent between 2000 and 2030 
(IPCC 2007, p. 44). If a resulting shift in the vegetative communities 
occurs within the range of the Wyoming pocket gopher, the displacement 
of native forbs and grasses could significantly alter the availability 
of sufficient forage resources. This could then be exacerbated by the 
continued loss of those resources as a result of the shortened fire 
cycle.
    Application of continental-scale climate change models to regional 
landscapes and even more local or ``step-down'' models projecting 
habitat potential based on climatic factors is informative, but 
contains a high level of uncertainty when predicting future effects to 
the Wyoming pocket gopher and its habitat due to a variety of factors, 
including regional weather patterns, local physiographic conditions, 
life stages of individual species, generation time of species, and 
species' reactions to changing carbon dioxide levels. The models 
summarized above are limited by these types of factors; therefore, 
their usefulness in assessing the threat of climate change on the 
Wyoming pocket gopher into the future is also limited.

Drought

    Drought conditions occur within the range of the Wyoming pocket 
gopher and are a natural process that has historically occurred 
separately from climate change. We anticipate natural drought cycles to 
occur periodically within the range of the Wyoming pocket gopher into 
the future. We could find no specific information regarding the effects 
of drought on the Wyoming pocket gopher. Presumably drought would 
likely affect forage growth and potentially limit food availability. 
While this may have temporary effects on population numbers and the 
reproductive ability of the Wyoming pocket gopher, the species 
continues to occupy its known range despite historic periods of natural 
drought.
Summary of Climate Change and Drought
    The direct, long-term impact from climate change to the Wyoming 
pocket gopher is not known. Shifts in the vegetative community may 
affect the species' ability to forage. However, given our lack of 
knowledge of important food resources for the Wyoming pocket gopher, 
our resulting lack of understanding about how changes in the forage 
base may affect the species, and our uncertainty regarding the effects 
of climate change on those food resources, we cannot consider climate 
change to be a threat to the species now, or in the foreseeable future. 
A reduction in forage availability may also occur during periods of 
drought. However, we have no data to facilitate our understanding of 
what impacts this may have on the species. Additionally, the Wyoming 
pocket gopher has persisted within its known range since at least 1857 
(Thaeler and Hinesley 1979, p. 480) despite periods of natural drought. 
Therefore, while there may be population variation as a result of 
drought, we do not have any data indicating that drought creates a 
threat to the Wyoming pocket gopher now, or in the foreseeable future.

Grazing

    Currently, livestock grazing is the most widespread type of land 
use across the sagebrush biome, which includes the known range of the 
Wyoming pocket gopher (Knick et al. 2003, p. 616; Connelly et al. 2004, 
pp. 7-29; Knick et al., in press, p. 27). Several studies have shown 
that livestock grazing can result in reduced pocket gopher abundance 
and in some cases complete exclusion (Phillips 1936, p. 676; Hunter 
1991, p. 117; Stromberg and Griffin 1996, p. 1205; Eviner and Chapin 
2003, p. 125). Livestock grazing has the potential to negatively affect 
pocket gophers through a variety of mechanisms, such as soil compaction 
(Phillips 1936, pp. 677-678). However, direct competition for forage 
likely has the largest negative effect on pocket gopher populations 
(Phillips 1936, p. 677). Wild ungulate grazing has been found to have 
similar competitive effects to other small mammals (Co[auml]te et al. 
2004, p. 129), and this interaction may impact pocket gophers. However, 
we have no information to suggest that this competition is occurring 
with the Wyoming pocket gopher.
    Historically, pocket gophers have been recognized by livestock 
producers as competitors with livestock for limited rangeland forage 
(Richens 1965, p. 424; Julander et al. 1969, p. 325; Turner

[[Page 19602]]

1969, p. 377; Laycock and Richardson 1975, p. 458). Pocket gophers 
primarily feed on forbs; however, diet composition can shift seasonally 
to include varying percentages of grasses and shrubs (see discussion 
above under Life History; Aldous 1951, pp. 85-86; Ward and Keith 1962, 
p. 747). Cattle are grazers, feeding mostly on grasses, but they will 
make seasonal use of forbs and shrub species (Vallentine 1990, p. 226). 
Domestic sheep are intermediate feeders, making high use of forbs but 
also using a large volume of grass and shrub species (Vallentine 1990, 
pp. 240-241). Horses are generalists, but seasonally their diets can be 
almost wholly comprised of grasses (Wagner 1983, pp. 119-120). The 
degree of competition between pocket gophers and livestock due to diet 
varies with local conditions that affect type and abundance of 
vegetation, stocking rates, and types of livestock (Phillips 1936, p. 
676; Eviner and Chapin 2003, p. 125). We are unable to assess the 
levels of competition that are occurring, but competition has likely 
remained constant since grazing levels on BLM lands have generally been 
stable since 1978 (Laycock et al. 1996, p. 50). We anticipate future 
levels of competition from grazing to remain constant, as the recently 
renewed BLM Resource Management Plan for much of the range of the 
Wyoming pocket gopher does not include a change in past livestock 
stocking rates (BLM 2008, pp. 2-19).
    Domestic livestock grazing will continue at present levels within 
the range of the Wyoming pocket gopher (BLM 2008, pp. 2-19). The 
current amounts, kinds, and seasons of livestock grazing use will be 
authorized until monitoring, field observations, ecological site 
inventory, or other data acceptable to the BLM indicates an adjustment 
to grazing use is necessary (BLM 2008, pp. 2-19). While we cannot 
provide an exact estimate of the foreseeable future for grazing, we 
expect this use to be persistent across the Wyoming pocket gopher's 
range for several decades.
    We recognize the potential for negative impacts to Wyoming pocket 
gopher populations due to direct competition with livestock, but have 
no information about the impacts of grazing practices or grazing 
intensity to the species. Livestock grazing has remained consistent 
over time, and the Wyoming pocket gopher has continued to occupy its 
known range. Additionally, we are unaware of any studies linking 
grazing practices to population levels of the Wyoming pocket gopher. 
Therefore, we have no information to indicate that grazing poses a 
threat to the Wyoming pocket gopher now, or in the foreseeable future.

Urbanization

    Urbanization is considered a significant threat to other species of 
pocket gopher, such as the Mazama pocket gopher (Service 2009b, p. 8); 
however, urbanization is limited within the range of the Wyoming pocket 
gopher. This area is largely rural, with approximately 55,000 people 
residing in Carbon and Sweetwater Counties in 2008 (U.S. Census Bureau 
2009, p. 94), which is an average of 3 people per square mile (2.6 
square kilometers). However, most of this population is concentrated in 
the population centers of Rock Springs, Green River, and Rawlins, which 
are at the edges of the potential Wyoming pocket gopher range. The BLM 
administers approximately half of the land in the range of the species, 
so urban development is precluded from those areas. Limited housing 
development is occurring near Wyoming pocket gopher collection sites, 
primarily to support gas field workers. These areas provide 
concentrated areas of disturbance, which create fewer impacts to the 
overall range of the species. The limited amount of housing across the 
range of the species also restricts the opportunities for domestic pet 
predation on Wyoming pocket gophers. We are unable to quantify a 
foreseeable future, but anticipate that additional urbanization will be 
limited based on the isolated nature of the area and the harsh 
environment that has not historically attracted many people. Based on 
the limited amount of urbanization, we do not consider it to be a 
significant threat to the Wyoming pocket gopher now, or in the 
foreseeable future.

Summary of Factor A

    We conclude that the range of the Wyoming pocket gopher has 
experienced and will continue to experience significant changes, 
primarily related to oil, gas, and wind development. The range is also 
likely to experience some changes related to climate change. Changes 
from other sources, including nonnative vegetation, grazing, and 
urbanization, may occur to a lesser degree. However, we are unable to 
demonstrate that these alterations to habitat will result in negative 
effects to the species. Examining data from studies on other species of 
pocket gophers' responses to similar disturbances did not provide 
clarity as the response appeared to vary by species. For example, the 
invasive Bromus tectorum may negatively affect pocket gophers, but 
northern pocket gophers can occur where B. tectorum is a prevalent 
plant species (Ostrow et al. 2002, p. 992), and the seeds of B. 
tectorum were occasionally found in their burrows (Cox 1989, pp. 78-
80). Many species of pocket gophers increase rates of mound building in 
areas of disturbed vegetation, while others are not found in areas of 
disturbance (Moulton et al. 1983, p. 58). Therefore, predicting the 
potential effects of habitat disturbances or alteration on the Wyoming 
pocket gopher based on the responses of other pocket gophers is not 
possible. The species continues to occupy its known historic range 
despite habitat alterations that have occurred within that range, and 
we have no evidence of population declines.
    We conclude that the best scien