Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List the Mohave Ground Squirrel as Endangered or Threatened, 62214-62258 [2011-25473]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 76, Number 194 (Thursday, October 6, 2011)]
[Proposed Rules]
[Pages 62214-62258]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-25473]



[[Page 62213]]

Vol. 76

Thursday,

No. 194

October 6, 2011

Part III





Department of the Interior





-----------------------------------------------------------------------





Fish and Wildlife Service





-----------------------------------------------------------------------





50 CFR Part 17





Endangered and Threatened Wildlife and Plants; 12-Month Finding on a 
Petition To List the Mohave Ground Squirrel as Endangered or 
Threatened; Proposed Rule

Federal Register / Vol. 76 , No. 194 / Thursday, October 6, 2011 / 
Proposed Rules

[[Page 62214]]


-----------------------------------------------------------------------

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R8-ES-2010-0006; 92210-1111-0000-B2]


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition To List the Mohave Ground Squirrel as Endangered or 
Threatened

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

-----------------------------------------------------------------------

SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding on a petition to list the Mohave ground squirrel 
(Spermophilus mohavensis) as endangered or threatened under the 
Endangered Species Act of 1973, as amended (Act). After review of the 
best available scientific and commercial information, we find that 
listing the Mohave ground squirrel is not warranted at this time. 
However, we ask the public to continue to submit to us any new 
information that becomes available concerning the threats to the Mohave 
ground squirrel or its habitat at any time.

DATES: The finding announced in this document was made on October 6, 
2011.

ADDRESSES: This finding is available on the Internet at https://www.regulations.gov at Docket Number FWS-R8-ES-2010-0006 and at https://www.fws.gov/ventura/. 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, Ventura 
Fish and Wildlife Office, 2493 Portola Road, Suite B, Ventura, CA 
93003. Please submit any new information, materials, comments, or 
questions concerning this finding to the above address.

FOR FURTHER INFORMATION CONTACT: Michael McCrary, Listing and Recovery 
Program Coordinator, U.S. Fish and Wildlife Service, Ventura Fish and 
Wildlife Office (see ADDRESSES); by telephone at 805-644-1766; or by 
facsimile at 805-644-3958. 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 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 contains substantial scientific or 
commercial information that listing may be warranted, we make a finding 
within 12 months of the date of receipt of the petition. In this 
finding, we determine whether the petitioned action is: (a) Not 
warranted, (b) warranted, or (c) 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 December 13, 1993, the Service received a petition dated 
December 6, 1993, from Dr. Glenn R. Stewart of California Polytechnic 
State University, Pomona, California, requesting the Service list the 
Mohave ground squirrel as a threatened species. At that time, the 
species was a category 2 candidate (November 15, 1994; 59 FR 58982), 
and was first included in this category on September 18, 1985. Category 
2 included taxa for which information in the Service's possession 
indicated that listing the species as endangered or threatened was 
possibly appropriate, but for which sufficient data on biological 
vulnerability and threats were not available to support a proposed 
listing rule. On September 7, 1995, we published our 90-day petition 
finding, which determined that the 1993 petition did not present 
substantial information indicating that the petitioned action may be 
warranted (60 FR 46569).
    On September 5, 2005, we received a petition, dated August 30, 
2005, from the Defenders of Wildlife and Dr. Glenn R. Stewart to list 
the Mohave ground squirrel as an endangered species in accordance with 
section 4 of the Act. It also requested that critical habitat be 
designated concurrent with the listing of the Mohave ground squirrel. 
The petition clearly identified itself as such and included the 
requisite identification information for the petitioners, as required 
in 50 CFR 424.14(a).
    On April 27, 2010, the Service made its 90-day finding (75 FR 
22063), concluding that the petition presented substantial scientific 
or commercial information to indicate that listing the Mohave ground 
squirrel may be warranted, announced the initiation of a status review 
of this species, and solicited comments and information to be provided 
in connection with the status review by June 28, 2010. This notice 
constitutes our 12-month finding regarding the petition to list the 
Mohave ground squirrel.

Species Information

Species Description
    The Mohave ground squirrel is a medium-sized squirrel. Total 
length, including the tail, is about 9 inches (in) (23 centimeters 
(cm)), tail length is about 2.5 in (6.4 cm), and weight is about 3.5 
ounces (104 grams). The upper body is grayish brown, pinkish gray, 
cinnamon gray, and pinkish cinnamon, without stripes or fleckings. The 
underparts of the body and the tail are silvery white and the tail is 
bushy (Grinnell and Dixon 1918, p. 667). The skin is darkly pigmented 
and dorsal hair tips are multi-banded. The Mohave ground squirrel has a 
winter and summer pelage (coat). In summer the pelage is coarser and 
shorter, the sides of the face paler, and the underbelly whiter than 
the winter pelage. The two sexes appear to be alike in color and 
measurements (Grinnell and Dixon 1918, p. 667).
    Two other species of small ground squirrels occur within the range 
of the Mohave ground squirrel, the antelope ground squirrel 
(Ammospermophilus leucurus) and the round-tailed ground squirrel 
(Xerospermophilus tereticaudus). The three species are different in 
appearance. Although similar in size to the Mohave ground squirrel, the 
antelope ground squirrel is grayish brown in color, with a white side 
stripe and a black band on the underside of the tail near the tip 
(Ingles 1965, pp. 169-171). The round-tailed ground squirrel has a 
unicolored tail that is cylindrical or round and not bushy, and a 
larger body than the Mohave ground squirrel (Ingles 1965, p. 171). 
However, its skull is significantly smaller than that of the Mohave 
ground squirrel in 18 of 20 cranial characteristics (Best 1995, p. 
508). Mohave and antelope ground squirrels occur sympatrically 
(occupying the same or overlapping geographic areas without 
interbreeding) in the same habitat (Aardahl and Roush 1985, p. 20), 
while round-tailed ground squirrels overlap only along the eastern edge 
of the Mohave ground squirrel's range (see ``Nomenclature and 
Taxonomy'' section below).

[[Page 62215]]

Nomenclature and Taxonomy
    The scientific name of the Mohave ground squirrel was changed from 
Spermophilus mohavensis to Xerospermophilus mohavensis with the 
publication of a review of the available research on morphological, 
genetic, cytogenetic, ecological, and behavioral attributes in the 
genus Spermophilus (Helgen et al. 2009, p. 273).
    The Mohave ground squirrel is a distinct, full species with no 
recognized subspecies. It was discovered in 1886 by Frank Stephens 
(Grinnell and Dixon 1918, p. 667) and described by Merriam (1889, p. 
15). The type specimen is from near Rabbit Springs, San Bernardino 
County, California, about 15 miles (mi) (24.1 kilometers (km)) east of 
Hesperia (Grinnell and Dixon 1918, p. 667).
    The closest relative of the Mohave ground squirrel is the round-
tailed ground squirrel (Bell et al. 2009, p. 5; Helgen et al. 2009, p. 
293). Until 1977, the ranges of these two species were thought to be 
adjacent to each other but not overlapping (Hall and Kelson 1959, p. 
358). However, Wessman (1977, p. 10) determined that the eastern edge 
of the geographic range of the Mohave ground squirrel overlapped the 
western edge of the round-tailed ground squirrel (Wessman 1977, pp. 12-
13). He identified several areas of contact between the two species and 
identified one area near Helendale, San Bernardino County, California, 
as a possible zone of hybridization between the species. He observed 
morphological characteristics of both species exhibited in a few of the 
squirrels captured there (e.g., long, narrow tail with white on the 
underside) (Wessman 1977, p. 13). However, in 2009, Bell et al. (p. 11) 
found no evidence of mitochondrial DNA introgression between the Mohave 
ground squirrel and the round-tailed ground squirrel, including the 
three individuals identified as backcross individuals based on allozyme 
(form of an enzyme that differs in amino acid sequence) and karyotypic 
(the shape, type, number, and order of a species' chromosomes) data 
from Hafner and Yates (1983). We are not aware of any information that 
would indicate hybridization occurs with the sympatric antelope ground 
squirrel.
Range and Distribution
    The Mohave ground squirrel is endemic to the western part of the 
Mojave Desert, in portions of Inyo, Kern, Los Angeles, and San 
Bernardino Counties, California. It has one of the smallest ranges of 
any species of ground squirrel in North America (Hoyt 1972, p. 3). We 
define range as the geographical area within which a species may be 
found.
    Aspects of the Mohave ground squirrel's biology and behavior make 
individuals of the species difficult to observe, trap, and count, which 
in part explains why the range of the species has increased over time 
(see below). Mohave ground squirrels are only active and above ground 
for part of the year (generally February through August) and therefore 
can only be trapped and observed during this time. They spend much of 
the year underground and in a state of dormancy (see ``Active Season 
and Dormancy'' section). The length of the active season and movements 
of Mohave ground squirrels may also be affected by rainfall amounts. 
The number of individuals in an area appears to decline during dry 
years, and movements and home range size shrink (Harris and Leitner 
2004, p. 521). Thus, if traps are set during a dry year, the reduced 
movements of Mohave ground squirrels and reduced densities or local 
extirpations make it less likely that the traps are located when and 
where they will capture Mohave ground squirrels. Conversely, if traps 
are set during a wet year when home ranges are larger, the Mohave 
ground squirrel may avoid the baited traps because of the increased 
availability of forage.
    Because most surveys for the Mohave ground squirrel have been only 
1 year in duration, this limited survey duration makes it difficult to 
assess population trend for a species whose numbers, movements, and 
``trapability'' can fluctuate greatly among years (Brooks and Matchett 
2002, p. 171). These factors in combination have made it difficult to 
determine the boundaries of the species' range, its distribution within 
the range, and population trends (see ``Abundance and Trends'' 
section). This has been further complicated because the vast majority 
of the information currently available on the distribution and 
abundance of Mohave ground squirrels is based on the California 
Department of Fish and Game (CDFG) survey protocol, which has been 
known to not detect squirrels when other methods have shown them to be 
present (see ``Abundance and Trend'' section below).
    In 1938, Howell (1938, p. 184) published a map of the range of the 
Mohave ground squirrel that included the western Antelope Valley to an 
area 15 mi (25.2 km) west of Barstow. In 1977, Wessman surveyed for the 
Mohave ground squirrel along much of its eastern boundary and found the 
species' range extended 1,152,000 ac (466,200 ha) farther east and 
south than previously reported (Wessman 1977, p. 4).
    For this 12-month finding, the Service is defining the range of the 
Mohave ground squirrel as about 5,319,000 acres (ac) (2,152,532 
hectares (ha)) (Service calculations) (see Map 1). The range is bounded 
on the south and west by the San Bernardino, San Gabriel, Tehachapi, 
and Sierra Nevada mountain ranges, although the species occurs in 
canyons in the eastern foothills of the Sierra Nevada up to 5,600 feet 
(ft) (1,706 meters (m)) (Gustafson 1993, pp. 56-57; Laabs 1998, p. 1). 
The range is bounded on the north and east by Owens Lake and the Mojave 
River/Lucerne Valley, respectively (Leitner 2008, p. 18). Howell (1938, 
p. 184) and Aardahl and Roush (1985, p. 3) included the Antelope Valley 
west of Palmdale and Lancaster in the range of the Mohave ground 
squirrel (see Map 1).
    The range map in the petition did not include the western Antelope 
Valley because there are no definite records of the species in that 
area. However, for several reasons, we included the western Antelope 
Valley in our range of the Mohave ground squirrel. First, older reports 
and scientific papers on the Mohave ground squirrel included this area 
in the range of the species (e.g., Howell 1938, p. 184; Aardahl and 
Roush 1985, p. 3). Second, although portions of this area are now used 
for agriculture and livestock grazing, suitable habitat still remains 
and may be connected to currently occupied habitat to the east. Third, 
early museum collections of the Mohave ground squirrel did not record 
precise locality data and often used the closest town for reference 
such as ``near Palmdale.'' Frequently, the closest town was several 
miles away and the locality information vague. Fourth, recent visual 
observations of Mohave ground squirrels occurred southwest of Mojave 
(see Map 1) (Leitner 2008, p. 7). Thus, there is some indication that 
the Mohave ground squirrel may have occurred, and may continue to 
occur, in the western portion of the Antelope Valley. Although areas of 
natural habitat within the range of the Mohave ground squirrel have 
been lost or degraded from human activity (see Factor A), the boundary 
of the current range is larger than reported by Howell in 1938.
    The range of the Mohave ground squirrel may be larger than defined 
by the Service, as there have been recent sightings beyond the area 
defined by the Service as the range of the Mohave ground squirrel. 
Although the Mohave ground squirrel has previously been reported at 
elevations up to 5,600 ft (1,706 m) in the canyons in the eastern 
foothills of the Sierra Nevada that open

[[Page 62216]]

to the Mojave Desert (Gustafson 1993, pp. 56-57; Laabs 1998, p. 1), a 
biologist recently reported a Mohave ground squirrel about 10 mi (16.1 
km) south of Weldon (see Map 1) in an interior valley in the Tehachapi 
Mountains (California Natural Diversity Database 2007). Another 
biologist sighted a Mohave ground squirrel in the Panamint Valley, 
which is about 5 mi (8 km) outside the northeastern edge of the range 
(see Map 1) (Threloff 2007 in litt., p.1), whereas Aardahl
BILLING CODE 4310-55-P
[GRAPHIC] [TIFF OMITTED] TP06OC11.000

BILLING CODE 4310-55-C

[[Page 62217]]

and Roush were unsuccessful in capturing a squirrel here in 1985 
(Gustafson 1993, p. 56). We are not using these two sightings in our 
range calculations because they are anecdotal and fall outside the 
areas previously published about the range of the Mohave ground 
squirrel. Although we have not included these two sightings, they 
indicate that the range of the Mohave ground squirrel may actually be 
larger than previously indicated on range maps or currently defined by 
the Service.
    Within its range, the Mohave ground squirrel has a patchy 
distribution (Hoyt 1972, p. 7), likely caused by differences in 
rainfall, terrain (Zembal and Gall 1980, p. 348), elevation, 
temperature (Gustafson 1993, pp. 56-57), and soils and vegetation 
(Harris and Leitner 2005, p. 189). The habitat requirements of the 
Mohave ground squirrel for feeding, breeding, and sheltering are not 
uniformly spaced throughout its range.
    Leitner (2008, pp. i-A2) collected and analyzed 1,236 unpublished 
observations, field studies, and surveys from 1998 to 2007, including 
both positive and negative findings of trapping efforts using the CDFG 
survey protocol. These surveys were usually performed in association 
with proposed development, because the Mohave ground squirrel is listed 
as threatened under the California Endangered Species Act (CESA) (see 
Factor D, ``State Laws and Regulations''). The survey effort has been 
heavily weighted to the southernmost portion of the species' range 
(Leitner 2008, p. 5), where most of the development in the range of the 
Mohave ground squirrel has occurred and is occurring (see Factor A, 
``Urban and Rural Development''). Approximately 67 percent of the 
surveys were conducted south of State Route 58 (SR-58) (see Map 1), and 
almost half of all surveys were in two areas in the southernmost part 
of the range of the Mohave ground squirrel: The Lancaster-Palmdale area 
and the Adelanto area. Almost all recorded observations of Mohave 
ground squirrels from 1998 to 2007 have been from Edwards Air Force 
Base (EAFB), which is south of SR-58 (see Map 1), or from the central 
and northern portion of the squirrel's range; only a few were observed 
in the southern end of the squirrel's range. However, much of the range 
of the Mohave ground squirrel has not been surveyed (Leitner 2008, p. 
9).
    Leitner (2008, p. 10) identified four areas that he labels as 
``core'' areas for the Mohave ground squirrel. ``Core'' areas have the 
following criteria:
    (1) The species has been present for a substantial period;
    (2) The species is currently found at multiple locations; and
    (3) There is a substantial number of adults representing a viable 
reproductive population.
    Four areas that meet the above criteria are: (1) Coso Range-
Olancha; (2) Little Dixie Wash; (3) EAFB; and (4) Coolgardie Mesa-
Superior Valley (see Map 2). Leitner (2008, p. 1) also described four 
other population areas with multiple recent records of the species, 
although these areas are not known to have Mohave ground squirrels 
present for a substantial period: Pilot Knob, the Desert Tortoise 
Natural Area-Fremont Valley, Boron-Kramer Junction, and Poison Canyon 
(Leitner 2008, p. 34). Together these eight important population areas 
comprise about 606,000 ac (245,240 ha), or 11.4 percent of the species' 
range.
BILLING CODE 4310-55-P

[[Page 62218]]

[GRAPHIC] [TIFF OMITTED] TP06OC11.001

BILLING CODE 4310-55-C
    Leitner has emphasized the importance of protecting and maintaining 
connectivity between these eight areas for the conservation of the 
Mohave ground squirrel (2008, p. 12). It should be noted, however, that 
these areas have been identified using the data available from limited 
surveys for the Mohave ground squirrel. Much of the range has not been 
surveyed (Leitner 2008, p. 9); therefore, unsurveyed areas may support 
additional important population areas for the Mohave ground squirrel. 
As an example of a recent discovery of an important population area, 
the Poison Canyon area was discovered during a 2006 survey for a 
proposed drainage improvement project

[[Page 62219]]

along a State highway (Sapphos 2006, p. 3-1).
Abundance and Trends
    Data on population abundance and trend for the Mohave ground 
squirrel are limited (Leitner 2008, p. 8). The behavioral 
characteristics of the Mohave ground squirrel make it difficult to 
determine its presence or abundance as it spends much of the year 
underground (see ``Active Season and Dormancy'' section below). Based 
on his observations, Burt (1936, p. 222) estimated the density of 
Mohave ground squirrels in the southern part of their range at 15 to 20 
animals per square mi (5 to 8 animals per square km). Most subsequent 
studies cannot be readily compared with Burt (1936) because they did 
not estimate density of animals (i.e., they either reported the number 
of animals trapped or compared numbers trapped to individual trapping 
efforts (Hoyt 1972, p. 6; Recht 1977, p. 4; Wessman 1977, p. 4; Leitner 
1980, pp. IV-26; Aardahl and Roush 1985, pp. 11-13; Scarry et al. 1996, 
pp. 12-17; Leitner 2001, pp. 13-18, 30-32).
    The only location we are aware of where a population of Mohave 
ground squirrels has been studied in detail for several years is in the 
Coso Region in the northern portion of the species' range (Leitner 
2005, p. 3). Trapping surveys for the Mohave ground squirrel at this 
location were conducted from 1989 to 1996 and from 2001 to 2005. 
However, the estimated population density was only reported for 1990 
and for the period from 1992 to 1996 because of limited sample size in 
other years (Leitner and Leitner 1998, pp. A-3, A-6, A-8, A-9, A-12, A-
15, A-18, and A-22). The number of Mohave ground squirrels that were 
captured varied from year to year, ranging from 10 squirrels trapped in 
2003 to 78 in 1994 (Leitner 2005, p. 3). The number of adult Mohave 
ground squirrels trapped was higher per year during the period 1990-
1996 than during the period 2001-2004 (Leitner 2005, p. 3).
    Researchers have suggested that trends in protocol survey data over 
time could be used to evaluate the status of the species. Brooks and 
Matchett (2002) analyzed the data from 19 reported studies on the 
Mohave ground squirrel in 1918 and during the period 1970-2001. They 
suggested that the Mohave ground squirrel may be undergoing a long-term 
decline as indicated by the decreased trapping success since the mid-
1980s (Brooks and Matchett 2002, p. 176). One possible reason for 
decline is that Mohave ground squirrel populations appear to be 
sensitive to both seasonal and annual rainfall patterns; for example, 
in dry years, reproduction the following spring may be unsuccessful, 
and population numbers and the area occupied by the species may 
decrease (Leitner and Leitner 1998, pp. 29-31; Harris and Leitner 2005, 
p. 520).
    Gustafson (1993, p. 22) reported that prolonged periods of drought 
may result in the loss of Mohave ground squirrels in local areas, 
because no young may be born for one up to several years, and adult 
survivability is reduced by poor habitat conditions to the point where 
the population dies out. In general, the population dynamics of the 
Mohave ground squirrel appear to follow a contraction and expansion 
pattern, i.e., there are local extirpations of squirrel populations 
following drought years and recolonization of these areas with 
consecutive wet years (Harris and Leitner 2005, p. 189). During the 
last few decades, more consecutive years in the western Mojave Desert 
have been dry versus wet (Brooks and Matchett 2002, p. 175), suggesting 
a trend weighted toward extirpations rather than recolonizations. 
However, Brooks and Matchett (2002, p. 176) suggest that factors other 
than, or in addition to, rainfall amount and timing seem to be 
affecting Mohave ground squirrel abundance, such as trapping 
characteristics, trapping protocols, weather conditions, or site 
(habitat) characteristics.
    Leitner (2001, pp. 30-31) conducted a similar comparison of 
trapping results at 11 sites in 1980, 1999, and 2000, and at 19 sites 
in 2004 (Leitner 2005, p. 5). The first study showed a positive 
correlation between rainfall and trapping success prior to 1991, but no 
correlation after that. Both studies reported that trapping success has 
declined and concluded that this indicated a possible decline in the 
distribution and abundance of the Mohave ground squirrel during this 
period, despite periods of above-normal precipitation (Leitner 2001, p. 
32; Brooks and Matchett 2002, p. 176).
    However, the survey protocol is subject to potential inaccuracies, 
such as yielding false negative results or undersampling the population 
(see also Factor D, ``State Laws and Regulations'' section). Mohave 
ground squirrels are difficult to trap (Hoyt 1972, p. 7), and they have 
been observed approaching traps but not entering them (Leitner 2009, 
pers. comm.). For example, in 2009, only one Mohave ground squirrel was 
trapped during two surveys conducted in the Fort Irwin western 
expansion area (Delaney and Leitner 2009, p. 9). However, the detection 
rate for a video detection system, which was used at the same time as 
the trapping was conducted, was much higher; the video system recorded 
nine Mohave ground squirrels compared to the one that was trapped 
(Delaney 2009, pp. 13-14).
Food Habits
    The diet of the Mohave ground squirrel consists of leaves (Recht 
1977, p. 75), flowers, fruits, and seeds (Leitner and Leitner 1992, p. 
12; Gustafson 1993, pp. 77-83) from a variety of plants; they also feed 
on fungi (Burt 1936, p. 223) and arthropods (caterpillars) when 
available (Zembal and Gall 1980, p. 345). When available in spring, 
new, tender, green vegetation makes up nearly all of the diet of the 
Mohave ground squirrel (Best 1995, p. 6). The Mohave ground squirrel is 
also known to eat alfalfa (Best 1995, p. 5).
    The Mohave ground squirrel forages on the ground, in the branches 
of shrubs, and, where present, in Yucca brevifolia (Joshua trees) 
(Johnson no date, p. 1). It caches food in its burrow for future use 
(Johnson no date, p. 1). It obtains water from its diet, but will drink 
water if available (Johnson no date, p. 1).
    Recht (1977, p. 80) categorized the foraging strategy of the Mohave 
ground squirrel as a facultative specialist. Because the availability 
of food resources fluctuates seasonally and annually in the Mojave 
Desert, the Mohave ground squirrel specializes in certain food species 
for short periods, but changes the foods it consumes as their 
availability changes. For example, in March 1994, the diet of the 
Mohave ground squirrel in the northern part of its range was 90 percent 
shrubs, 10 percent forbs (i.e., any herbaceous plant that is not grass 
or grasslike), and less than 1 percent nonnative annual grasses 
(Schismus and Bromus) (Leitner et al. 1995, p. 45). By April, the 
Mohave ground squirrel's diet had changed to 60 percent shrubs, 35 to 
40 percent forbs, and 2 percent grasses (Leitner et al. 1995, p. 48).
    The quantity, variety, and nutritional quality of plant food 
sources available ultimately depend on the amount of rainfall from the 
preceding fall and winter (Aardahl and Roush 1985, p. 22). During 
drought years, there are few-to-no herbaceous native annual forbs 
available, and Mohave ground squirrels must then depend on shrub 
foliage for water and nutrition (Leitner and Leitner 1998, p. 20).
    This foraging strategy provides efficiency and flexibility to 
maximize nutritional and water intake in a changing desert habitat 
(Recht 1977, p. 80). These abilities are needed, as the Mohave ground 
squirrel must increase

[[Page 62220]]

its body weight in spring and early summer to sustain itself during the 
dormant period of mid-summer through winter (Leitner and Leitner 1998, 
p. 33).
Reproduction
    Female Mohave ground squirrels can breed at 1 year of age if 
environmental conditions are favorable (Leitner and Leitner 1998, p. 
28), while males do not breed until 2 years of age or older (Leitner 
and Leitner 1998, p. 36).
    The Mohave ground squirrel mating season occurs from mid-February 
to mid-March (Harris and Leitner 2004, p. 1). Mohave ground squirrel 
males typically emerge from dormancy in February, up to 2 weeks before 
females (Recht pers. comm., as cited in Gustafson 1993, p. 83). Male 
Mohave ground squirrels defend a territory, which females enter for 
mating (Recht pers. comm., as cited in Gustafson 1993, pp. 83-84). 
Three to four females mate and remain in the male's territory for a day 
or so, before returning to their respective home ranges. After a 
gestation period of 29 to 30 days, the young are born in the female's 
burrow (natal burrow) from March to May, with a peak in April. Average 
litter size is about six (Burt 1936, p. 224; Recht pers. comm., as 
cited by Leitner et al. 1991, p. 63) and ranges from four to nine (Best 
1995, p. 3). Parental care continues through mid-May, with juveniles 
emerging above ground at 10 days to 2 weeks of age (Gustafson 1993, p. 
84). By early May, the juveniles are active above ground and can be 
captured in live traps.
    Reproductive success appears to be strongly influenced by rainfall. 
In dry years, the Mohave ground squirrel's survival strategy appears to 
be to forego reproductive activity and concentrate on gaining weight 
and fat reserves in the spring and early summer to better survive the 
dormant period (Leitner and Leitner 1998, p. 32). For example, Mohave 
ground squirrels in the Coso Range failed to reproduce successfully in 
1989, 1990, and 1994, which correlated with low fall and winter 
precipitation and a low standing crop of annual forbs. In each of the 3 
years, precipitation during the period when it normally occurs in the 
region (September 1 to March 31) was lower than the long-term average 
for the same period (average of 3.3 in (8.5 cm) versus the average of 5 
in (12.7 cm), respectively) (Leitner and Leitner 1998, pp. 18-19, 21, 
and 29). In years when reproduction does occur, females of all age 
classes (including yearlings) produce young (Leitner and Leitner 1998, 
p. 28).
Mortality and Predation
    Mohave ground squirrels can live up to 5 years or longer (Leitner 
and Leitner 1998, p. 28). Mortality for juveniles is high during the 
first year and is disproportionately higher for males than females. As 
a result, the juvenile population contains significantly more females 
than males, and the adult female-to-male ratio averages about 2.6:1, 
but was reported to be as high as 7:1 in one population (Leitner and 
Leitner 1998, p. 36).
    Information on the causes of mortality in the Mohave ground 
squirrel is limited. We are not aware of any information on diseases in 
the species. Although not based on direct observation, predators are 
believed to include coyote (Canis latrans), American badger (Taxidea 
taxus), golden eagle (Aquila chrysaetos), red-tailed hawk (Buteo 
jamaicensis), prairie falcon (Falco mexicanus), common raven (Corvus 
corax), and rattlesnake (Crotalus sp.) (Boarman 1993, p. 2; Gustafson 
1993, p. 88; Harris, pers. comm., as cited in Defenders of Wildlife and 
Stewart 2005, p. 15).
    Mortality may also be caused by extended periods of low amounts of 
winter rainfall, which results in reduced availability of forage and 
water and increases the species' vulnerability to malnutrition, 
disease, and starvation. Gustafson (1993, p. 22) indicated that 
prolonged periods of drought result in the extirpation of Mohave ground 
squirrels in local areas as adult survival is reduced by poor forage 
conditions.
Active Season and Dormancy
    The Mohave ground squirrel lives in burrows which it digs 
(Gustafson 1993, p. ix), and remains in burrows in a state of dormancy 
throughout much of the year. For the Mohave ground squirrel, dormancy 
is a physiological state that includes a reduced frequency of 
breathing, or apnea, reduced oxygen consumption, reduced body 
temperature (Bartholomew and Hudson 1960, pp. 195-197), and a reduced 
heart rate (Ingles 1965, p. 177). Mohave ground squirrels may be active 
from February to August (Bartholomew and Hudson 1960, p. 194), with 
dormancy usually beginning in July or August; emergence dates vary with 
elevation (Johnson no date, p. 1). In years when reproduction occurs, 
most adults are active through June, but all have entered dormancy by 
the end of July; in years with no reproduction, adults may enter 
dormancy as early as the end of April. In contrast, juvenile Mohave 
ground squirrels begin to forage outside their natal burrows by mid-May 
and do not enter dormancy until July at the earliest and as late as the 
end of August (Leitner and Leitner 1998, pp. 32, 38).
    The period when dormancy begins varies annually. Dormancy does not 
appear to be an adaptation to avoid low temperatures; rather it appears 
to be an adaptation to seasonally restricted food and water 
(Bartholomew and Hudson 1960, p. 202). The initiation of dormancy 
appears to correspond to either the absence of available green 
vegetation or its abundance (Aardahl and Roush 1985, pp. 20-21). For 
the latter, the Mohave ground squirrel enters dormancy earlier as food 
abundance allows the animal to meet energy needs to sustain it through 
dormancy earlier (Harris and Leitner 2004, p. 521).
    The principal source of energy for the Mohave ground squirrel 
during dormancy is stored body fat, although food is stored in burrows 
and may be consumed during the dormant period (Ingles 1965, p. 177; 
Recht 1977, p. 85; Johnson no date, p. 1). During more severe drought 
years, Mohave ground squirrels may enter dormancy with relatively low 
body weight, which likely affects survivorship of Mohave ground 
squirrels, especially juveniles, to the following spring (Leitner and 
Leitner 1998, p. 32).
Home Range and Movements
    In general, juvenile Mohave ground squirrels have larger home 
ranges (at least twice as large) than adults, and adult males have 
larger home ranges than females (Aardahl and Roush 1985, p. 11; Best 
1995, p. 6). Mohave ground squirrels are territorial and, throughout 
much of their active period, there is little overlap between home 
ranges (Recht 1977, p. 20). Best (1995, p. 6) observed that home ranges 
are separate until late June, with little evidence of territorial 
behavior. The home ranges are not static and may shift during the 
active season, and from year to year, in response to changes in food 
quality and quantity (Best 1995, p. 6; Harris and Leitner 2004, p. 
520). Home ranges of juveniles form a cluster around the home range of 
an adult (Best 1995, p. 6), and adults exclude juveniles from those 
portions of the habitat with the densest vegetation (Best 1995, p. 6). 
Adult Mohave ground squirrels gain weight twice as fast as most 
juveniles, likely due to differences in resource quality between adult 
and juvenile home ranges (Recht 1977, p. 82).
    Home range size varies with the reproductive period and rainfall 
levels and food availability (Harris and Leitner 2004, p. 1). During 
the mating season, the median male home range is much

[[Page 62221]]

larger than the female home range, 16.6 ac (6.73 ha) compared to 1.8 ac 
(0.74 ha) (Harris and Leitner 2004, pp. 521-522). The females' home 
ranges are non-overlapping and noncontiguous, and each individual 
exhibits a high degree of site fidelity (Harris and Leitner 2004, p. 
522). During the post-mating period, male home range size varies from 
3.7 to 26.7 ac (1.5 to 10.8 ha), while female home range size varies 
from 0.72 to 4.69 ac (0.29 to 1.90 ha) (Harris and Leitner 2004, pp. 
517, 521). Female post-mating home range size is larger than the mating 
season home range (Harris and Leitner 2004, p. 520).
    An evaluation of different sequential survey results indicated that 
juvenile Mohave ground squirrels moved farther than adults (Aardahl and 
Roush 1985, p. 11), and long-distance movements were greater in males 
than in females. Among juveniles, the greatest long-distance movements 
between two sites for males (n = 15) was a mean of 4,987 ft (1,520 m) 
(range 360-20,440 ft (110-6,230 m)), and for females (n = 21) 1,657 ft 
(505 m) (range 344-12,670 ft (105-3,862 m)) (Harris and Leitner 2005, 
p. 188).
    Both adult male and female Mohave ground squirrels vocalize during 
their active season, and have multiple types of calls (Delaney 2009, 
pp. 15-17). The purpose of these calls is unknown but may be linked to 
identifying home ranges.
Habitat Requirements
    The Mohave ground squirrel occurs in a wide variety of habitats in 
the western Mojave Desert (Wessman, as cited in Aardahl and Roush 1985, 
p. 22). They include Mojave creosote bush scrub, Mojave mixed woody 
scrub, desert saltbush scrub, blackbrush scrub, Mojave desert wash 
scrub, Joshua-tree woodland, and shadescale scrub (Gustafson 1993, pp. 
ix, 81; Bureau of Land Management (BLM) 1998, p. 1); Mojave creosote 
bush scrub is the preferred habitat of the Mohave ground squirrel 
(Aardahl and Roush 1985, pp. 22, 23). The Mohave ground squirrel has 
also been found in some areas used for agriculture (Gustafson 1993, pp. 
ix, 81; BLM 1998, p. 1).
    Habitat features considered most suitable for the Mohave ground 
squirrel include areas with relatively flat topography, often located 
in large alluvial-filled valleys, containing fine-to-medium-textured 
soil with little or no rocks, and with the presence of a variety of 
native shrubs, including Larrea tridentata (creosote bush), Ambrosia 
dumosa (white bursage), and Atriplex spp. (saltbush) (Aardahl and Roush 
1985, p. 9).
    Soil characteristics are important, as the Mohave ground squirrel 
constructs burrows to escape temperature and humidity extremes and 
predators, and to give birth (Aardahl and Roush 1985, p. 23). The 
species is absent from very rocky areas and playas (i.e., a sandy, 
salty, or mud-caked flat floor of a desert drainage basin that is 
periodically covered with water) (Wessman 1977, pp. 7-9; Zembal and 
Gall 1980, p. 348). Rainfall must be adequate as it affects the quality 
and quantity of forage (Gustafson 1993, p. 57). Plant species diversity 
and the availability of native annual forbs are important to population 
stability and reproduction (Aardahl and Roush 1985, p. 22). The 
presence of a variety of shrubs that provide a reliable food source 
during drought years may be critical for a population to persist 
(Charis 2005, pp. 3-75).
    The Mohave ground squirrel is considered to be absent, or nearly 
so, from dry lakebeds, lava flows, and steep, rocky slopes, although 
juveniles may disperse through such areas (Leitner, pers. comm., as 
cited in Laabs 1998, p. 3). Harris and Leitner (2005, p. 193) found 
that Mohave ground squirrels travelled through habitats considered 
marginal for permanent occupancy (e.g., contained rocky or gravelly 
soils, and elevation changes of hundreds of feet) but did not cross a 
playa barren of vegetation. Long-distance movement by juveniles through 
marginal areas may be critical for connecting local populations and 
recolonizing sites after local, drought-related extirpations (Harris 
and Leitner 2005, p. 1).

Summary of Information Pertaining to the Five Factors

    Section 4 of the Act (16 U.S.C. 1533) and implementing regulations 
(50 CFR part 424) set forth procedures for adding species to, removing 
species from, or reclassifying species on the Federal Lists of 
Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of 
the Act, a species may 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.
    In making this 12-month finding, information pertaining to the 
Mohave ground squirrel in relation to the five factors provided in 
section 4(a)(1) of the Act is discussed below.
    In making our 12-month finding on a petition to list the Mohave 
ground squirrel, we considered and evaluated the best available 
scientific and commercial information. To ensure that this finding is 
based on the latest scientific information, we contacted species 
experts; land managers within the range of the Mohave ground squirrel; 
the CDFG; and others with expertise on the species, its habitat, and 
threats occurring, or likely to occur, within the range of the species. 
We conducted a search of the available published literature on the 
Mohave ground squirrel and collected unpublished reports on the species 
from resource agencies and others. Unpublished reports included 
regional field studies by State and Federal agencies and conservation 
groups, results of presence/absence surveys conducted prior to proposed 
development, and incidental observations reported by field biologists. 
In addition, we accessed information in the California Natural 
Diversity Database. This information, information provided by the 
public, and additional information and data in our files provided the 
basis for the status review for the Mohave ground squirrel. In making 
our 12-month finding, we considered and evaluated all scientific and 
commercial information in our files, including information received 
during the public comment period that ended June 28, 2010. The analysis 
of potential threats to the Mohave ground squirrel discussed below 
includes those identified in the petition and those identified in the 
information sources listed above.
    In considering what factors might constitute threats to a species, 
we must look beyond the exposure of the species to a particular factor 
to evaluate whether the species may respond to that factor in a way 
that causes actual impacts to the species. If there is exposure to a 
factor and the species responds negatively, the factor may be a threat 
and, during the status review, we attempt to determine how significant 
a threat it is. The threat is significant if it drives or contributes 
to the risk of extinction of the species such that the species warrants 
listing as endangered or threatened as those terms are defined in the 
Act. However, the identification of factors that could impact a species 
negatively may not be sufficient to compel a finding that the species 
warrants listing. The information must

[[Page 62222]]

include evidence sufficient to suggest that the potential threat has 
the capacity (i.e., it should be of sufficient magnitude and extent) to 
affect the species' status such that it meets the definition of 
endangered or threatened under the Act.

Factor A: The Present or Threatened Destruction, Modification, or 
Curtailment of the Species' Habitat or Range

    The following potential threats that may affect the habitat or 
range of the Mohave ground squirrel are discussed in this section: (1) 
Urban and rural development, (2) off-highway vehicle (OHV) recreational 
use, (3) transportation infrastructure, (4) military operations, (5) 
energy development, (6) livestock grazing, (7) agriculture, (8) mining, 
and (9) climate change. Climate change is discussed under Factor A 
because, although climate change may affect Mohave ground squirrels 
directly by creating physiological stress, the primary impact of 
climate change on the species is expected to be through changes to the 
availability and distribution of Mohave ground squirrel habitat. In 
addition, commercial filming occurs on private and Bureau of Land 
Management (BLM) lands in the western Mojave Desert. The activities for 
creating motion pictures, television shows, and commercials may require 
travelling on unpaved roads and trails or cross-country use. However, 
in our review of the best available scientific and commercial 
information, we did not find information that indicates these filming 
activities have occurred, are presently occurring, or are likely to 
occur in the future within Mohave ground squirrel habitat, and 
therefore, we have determined that they are not a threat to the 
species.
Urban and Rural Development
    The present and projected future growth of urban areas in the 
western Mojave Desert could adversely affect the Mohave ground 
squirrel. About 136,900 ac (55,426 ha), or 2.6 percent of the 5,319,000 
ac (2,152,532 ha) range of the Mohave ground squirrel (see Background 
section), has been lost to urban and rural development (Defenders of 
Wildlife and Stewart 2005, pp. 19, 38). Loss of Mohave ground squirrel 
habitat has occurred from the construction of residential homes, 
commercial and industrial complexes, shopping malls, golf courses, 
airports and associated commercial and industrial development, roads, 
landfills, wastewater treatment facilities, prisons, flood management 
structures, and other facilities.
    Most urban and rural development has occurred in valleys, flats, 
and gently sloping areas, which are the same types of areas most often 
used by Mohave ground squirrels. The greatest losses of Mohave ground 
squirrel habitat have occurred in, and adjacent to, cities including 
Palmdale, Lancaster, Victorville, Adelanto, Hesperia, Apple Valley, 
Barstow, and Ridgecrest, California (see Map 1). Smaller areas have 
also been lost at the towns of Hinkley, Boron, North Edwards, 
California City, Mojave, Rosamond, Inyokern, and Littlerock, and the 
unincorporated communities of Pearblossom, Phelan, and Pinyon Hills, 
California (see Map 1).
    Most of this urban development has occurred in the southernmost 
portion of the Mohave ground squirrel's range on private land, 
generally south of SR-58 (see Map 1). More than 62 percent of the 
private land within the range of the Mohave ground squirrel is south of 
SR-58. The three cities with the largest developed areas within the 
range of the squirrel (i.e., Lancaster, Palmdale, and Victorville) 
occur in this area, as do several of the smaller towns listed above 
(see Map 1). Some of this area has also been converted to agriculture 
(see ``Agriculture'' section below), and there are areas that do not 
contain suitable habitat for the squirrel (e.g., dry lake beds). We 
estimate the portion of the range of the Mohave ground squirrel south 
of SR-58 to be 1,690,797 ac (684,244 ha), or about 31.8 percent of the 
range of the Mohave ground squirrel (see Background section for our 
range analysis). Urbanization in this area is mainly concentrated along 
the southern edge of the squirrel's range, and much of the area south 
of SR-58 is undeveloped.
    Trapping results in the southern portion of the Mohave ground 
squirrel's range have generally been negative, especially in areas that 
are most heavily developed (Leitner 2008, p. 5). Mohave ground 
squirrels are currently known to occur in several areas south of SR-58, 
including one of the largest concentrations of squirrels on EAFB (see 
below). Recent records of the Mohave ground squirrel south of SR-58 and 
outside EAFB include two in the Victor Valley-Lucerne Valley area 
(Jones pers. comm., as cited in Defenders of Wildlife and Stewart 2005, 
p. 8), four records near Adelanto (Leitner 2008, p. 7), three records 
west and south of Barstow (Leitner 2008, pp. 7-8), and two records 
southwest of the town of Mojave (Leitner 2008, pp. 7-8).
    The fact that trapping results south of SR-58 have generally been 
negative does not necessarily mean that the Mohave ground squirrel is 
absent from the area or the area does not provide habitat for the 
species (Leitner 2008, p. 9). Negative trapping results can occur for 
various reasons, including trap location, time of trapping, and food 
availability (Brooks and Matchett 2002, p. 172; Leitner 2008, p. 9) 
(see ``Range and Distribution'' section and Factor D, ``State Laws and 
Regulations,'' for further discussion of the survey protocol).
    As discussed in the Background section, trapping surveys south of 
SR-58 have most often been conducted in areas where the squirrel has 
already been extirpated due to extensive urbanization, such as the 
Palmdale-Lancaster area in the southwestern portion of the range 
(Leitner 2008, p. 3). More importantly, large areas south of SR-58 have 
either never been surveyed or have been surveyed only 1-2 times 
(Leitner 2008, pp. 5, 9, 25). In addition, the trapping protocol that 
was used may not be the most effective method to determine the presence 
or absence of Mohave ground squirrels. Some scientists have identified 
potential problems with the protocol that raise questions about the 
accuracy of the current survey technique (Brooks and Matchett 2002, p. 
172) (see Factor D, ``State Laws and Regulations,'' for further 
discussion of the survey protocol).
    Federal lands comprise 28.5 percent of the area south of SR-58 (9.3 
percent of the total range of the Mohave ground squirrel). One of the 
more important concentrations of Mohave ground squirrels south of SR-58 
is on EAFB. The 307,435 ac (124,468 ha) EAFB encompasses about 18 
percent of the area south of SR-58 (5.8 percent of the range of the 
Mohave ground squirrel) and contains one of the eight important 
population areas for the Mohave ground squirrel (Leitner 2008, p. 10; 
se Map 2 and Background section). EAFB is used primarily for testing 
and evaluating aircraft, and the impacts to Mohave ground squirrel 
habitat from urban and rural development are primarily confined to the 
small cantonment areas (see ``Military Operations'' section below for 
details).
    In addition to the Federal lands on EAFB, there are more than 
175,000 ac (70,820 ha) of Federal land managed by the BLM south of SR-
58, all of which is not subject to the direct impacts of urbanization. 
These BLM lands include the southern part of the Fremont-Kramer Desert 
Wildlife Management Area (DWMA), which is managed for Mohave ground 
squirrel habitat. Urban and rural development will not occur on these 
lands (however, see ``Off-Highway

[[Page 62223]]

Vehicle Recreational Use,'' ``Military Operations,'' and ``Energy 
Development'' sections below for a discussion on other activities that 
may affect these areas managed by EAFB and the BLM).
    We expect that further urbanization of privately owned lands south 
of SR-58 will occur in the future. The population of the western Mojave 
Desert is projected to grow from 795,000 (in 2000) to more than 1.5 
million people by 2035 (BLM et al. 2005, p. 244). Most incorporated 
cities and communities in the western Mojave Desert have general or 
community plans that describe their growth and development for the next 
20 years or more. We estimate that about 475,000 ac (192,226 ha), or 
about 8.9 percent of the entire range of the Mohave ground squirrel, is 
incorporated. The majority (about 70 percent) of the incorporated land 
south of SR-58 occurs within the cities of Palmdale, Lancaster, 
Victorville, Apple Valley, Hesperia, Adelanto, and Barstow. Although 
these areas are already extensively urbanized, not all of the 
incorporated lands south of SR-58 are developed, and future growth is 
expected to occur in these areas. Under a worst-case scenario, all 
areas within the incorporated boundaries could be developed in the 
future.
    We did not find any information on major proposed urban 
developments or new communities being planned in the unincorporated and 
rural lands south of SR-58, although the existing unincorporated 
communities will likely continue to grow. However, we expect that 
future development will most likely occur in areas that are already 
incorporated because of proximity to existing infrastructure. Although 
we cannot predict with any certainty what areas will be developed or 
when they may be developed in the next 20-30 years, even if all 
incorporated lands south of SR-58 were developed, more than 475,000 ac 
(161,875 ha) would likely remain under Federal ownership south of SR-
58. Much of this land is in the Fremont-Kramer DWMA, which the BLM 
designated for management of Mohave ground squirrel habitat, and 
includes the important population area for the Mohave ground squirrel 
at EAFB (Leitner 2008, p. 10) (see Map 2). Except for possibly minor 
additions to the cantonment areas of EAFB, the Federal land south of 
SR-58 is not subject to urban and rural development.
    About 3,648,830 ac (1,476,635 ha) or 68.6 percent of the range of 
the Mohave ground squirrel is north of SR-58. This area comprises the 
central and northern portions of the range of the Mohave ground 
squirrel. Most of this land has not experienced urban development; 
rather, urbanization is limited and concentrated mainly around 
Ridgecrest and California City. About 144,000 ac (58,275 ha), or 3.9 
percent of the Mohave ground squirrel's range north of SR-58, is 
incorporated, almost all of which (90 percent) is within California 
City (BLM et al. 2005, chapter 3, p. 2). California City was 
incorporated in 1965, and although it is the third largest city in 
California in area, the population has grown to only about 14,120 in 
the 46 years since it was incorporated. Additionally, most of the 
incorporated area remains undeveloped. Given the slow growth rate of 
California City, we believe that much of the land within its 
incorporated boundaries will likely remain undeveloped.
    Federal lands managed by the BLM and Department of Defense (DOD) 
make up about 80 percent (2,109,326 ac (853,617 ha)) of the range of 
the Mohave ground squirrel north of SR-58 (39.7 percent of the entire 
range). The BLM manages 438,364 ac (177, 400 ha), while the DOD manages 
1,670,962 ac (676,217 ha). Most of the 1,110,443-ac (449,382-ha) China 
Lake Naval Air Weapons Station (NAWS) and the 33,359-ac (13,500-ha) 
Goldstone Deep Space Communications Complex (Goldstone Complex), 
managed by the National Aeronautical and Space Administration (NASA), 
experience little habitat disturbance. Seven of the eight Mohave ground 
squirrel important population areas are located north of SR-58, occur 
mostly or entirely on Federal land (see Map 2), and are not subject to 
urban development on Federal land. We do not expect any urbanization to 
occur on BLM land. Because of their missions, we anticipate minimal 
future urban development on the military bases; any development will 
likely be limited to the cantonment areas (see ``Military Operations'' 
section).
    In summary, we recognize that some Mohave ground squirrel habitat 
has been lost to development within the range of the squirrel. 
Currently, about 2.6 percent of the range of the Mohave ground squirrel 
has been lost to development, and we expect that more of the range will 
be lost in the future, most likely adjacent to existing urban areas. A 
worst-case scenario would be that all incorporated land (about 8.9 
percent (475,000 ac (192,226 ha)) within the range of the squirrel is 
developed. Although unlikely because of the expected slow growth of 
California City, even if this were to occur, 62 percent (3,300,000 ac 
(1,335,468 ha)) of the squirrel's range is federally owned, very little 
of which is subject to urban development. We estimate that about 57 
percent of the Federal lands (EAFB, NAWS, Goldstone Complex, DWMAs, and 
Mohave Ground Squirrel Conservation Areas (MGSCA)) are managed, at 
least in part, for Mohave ground squirrel habitat (see Map 2, Table 1, 
and Factor D, ``Federal Laws and Regulations''). The eight important 
population areas for the Mohave ground squirrel occur mostly or 
entirely within Federal lands managed in part for the Mohave ground 
squirrel, and are therefore not threatened with urban development. In 
addition, Leitner (2008, p. 9) has stated that additional populations 
of the Mohave ground squirrel may well exist because much of the range 
of the squirrel has never been surveyed or has only been surveyed 1-2 
times, which may not be sufficient to determine the presence of the 
squirrel (Leitner 2008, p. 25). We conclude, based on this assessment, 
that urban and rural development does not currently pose a threat to 
the Mohave ground squirrel in relation to the present or threatened 
destruction, modification, or curtailment of its habitat or range, nor 
do we anticipate it posing a threat in the future.

  Table 1--Federal Lands Managed for the Mohave Ground Squirrel or Its Habitat, and the Percent of the Species'
                                                    Range \1\
----------------------------------------------------------------------------------------------------------------
                                                                   Percent of Mohave ground squirrel range
                                                           -----------------------------------------------------
                                                                                State/private      Total area
      Management areas for the Mohave ground squirrel            Federal        ownership \2\        within
                                                                ownership          within        management area
                                                                               management area      boundary
----------------------------------------------------------------------------------------------------------------
Mohave Ground Squirrel Conservation Area \3\..............              16.7               7.9              24.6
Department of Defense--Limited Use/Protected..............              27.0                 0              27.0

[[Page 62224]]

 
Bureau of Land Management ACECs \4\ (Fremont-Kramer Desert              13.6               8.5              22.1
 Wildlife Management Area, Superior-Cronese Desert
 Wildlife Management Area, Desert Tortoise Research
 Natural Area) \3\........................................
                                                           -----------------------------------------------------
    Total.................................................              57.3              16.4              73.7
----------------------------------------------------------------------------------------------------------------
\1\ Species' range is 5,319,000 ac (2,152,532 ha) as calculated by the Service.
\2\ State/private ownership is not specifically managed for the Mohave ground squirrel.
\3\ Land ownership within designated boundary includes Federal, State, and privately-owned lands.
\4\ Area of Critical Environmental Concern.

Off-Highway Vehicle Recreational Use
    Off-highway vehicle (OHV) use is any use that includes driving a 
motorized vehicle off a paved road, including driving cross country and 
on existing dirt roads. OHV use has the potential to adversely affect 
the Mohave ground squirrel by crushing individuals (see Factor E, 
``Direct Mortality'') and their burrows (Bury et al. 1977, p. 16), 
damaging or destroying native vegetation, and compacting soils. Burrows 
are essential to the survival of the Mohave ground squirrel, as they 
provide protection from predation and the temperature extremes of the 
desert, are likely used to store food, and provide a safe location for 
reproduction and rearing young. Impacts to vegetation increase the 
exposure of the Mohave ground squirrel to predators, decrease available 
shade for thermoregulation, and increase soil temperature extremes, 
which adversely affect plant germination, growth (Boarman 2002, p. 47), 
and food availability. Compacted soils reduce the infiltration rate of 
rain, which means there is less water available for plants and seed 
germination (Boarman 2002, p. 46), reduce the root growth of 
established plants, and make it harder for seedlings to survive (Lovich 
and Bainbridge 1999, p. 316). With soil compaction, soil erosion from 
wind and water increases, nitrogen fixation is reduced, less organic 
material is available for plant growth, and seedling establishment is 
reduced (Lovich and Bainbridge 1999, pp. 315-316; Boarman 2002, pp. 45-
46).
    OHVs also transport nonnative annual seeds and plant parts from 
other locations. Their roads, trails, and tracks act as dispersal 
corridors for invasive annual plant species (Lovich and Bainbridge 
1999, p. 313). These nonnative species suppress the growth of native 
annual forbs (Brooks 2000, p. 105), which are a source of food and 
water for the Mohave ground squirrel. Many native annual plants have a 
higher percentage of water and protein than nonnative plants (Oftedal 
et al. 2002, p. 344); however, we have no information on the Mohave 
ground squirrel's nutritional needs and their use of nonnative plants.
    Other potential impacts of OHV use include: Noise, which can cause 
hearing loss in rodents (Lovich and Bainbridge 1999, p. 316) and may 
interfere with the Mohave ground squirrel's ability to detect predators 
and establish and maintain territories (Bury et al. 1977, p. 16); 
littering and dumping of garbage (BLM 2003, p. 31), which can attract 
Mohave ground squirrel predators (see Factor C, ``Predation''); and 
increased fire sources (BLM 2003, p. 32), such as campfires and 
cigarettes, which can result in fires that destroy Mohave ground 
squirrel habitat.
    In the western Mojave Desert, the BLM manages its lands for OHV 
recreation. The BLM has designated four open areas (i.e., OHV 
management areas) within the range of the Mohave ground squirrel as 
open to all OHV use, including cross-country use (BLM et al. 2005, 
chapter 3, pp. 242-243). The four OHV management areas within the range 
of the Mohave ground squirrel are: (1) Dove Springs (3,840 ac (1,554 
ha)); (2) El Mirage (25,600 acres (10,360 ha)); (3) Jawbone Canyon 
(3,827 ac (9,642 ha)); and (4) Spangler Hills (62,080 acres (25,123 
ha)) (BLM et al. 2005, chapter 3, pp. 243, 244; Service GIS data) (see 
Map 2). These four areas comprise 95,347 ac (38,586 ha) (BLM 2003, p. 
31), or 1.8 percent of the range of the Mohave ground squirrel. Outside 
of these four areas, the BLM restricts OHV use to specific existing 
roads and trails, and cross-country use is prohibited (BLM et al. 2005, 
chapter 3, pp. 264-273). We are not aware of any plans on the part of 
the BLM to designate new OHV management areas in the future.
    The impacts from OHV use to the Mohave ground squirrel and its 
habitat vary depending on the type of OHV activity, the designated land 
use, and the level of enforcement. The impacts to the Mohave ground 
squirrel and its habitat are greatest in open areas and high-OHV-use 
areas (e.g., staging areas for OHV events, camping areas), and less in 
areas where activities are confined to existing roads and trails.
    Cross-country OHV use is restricted to the four management areas; 
however, the occurrence of off-route OHV use tends to extend or spill 
over into areas immediately adjacent to the management areas. Although 
the impacts to Mohave ground squirrels likely diminish with distance 
from the management areas, the BLM estimates that these ``spill-over'' 
zones, some of which are on private land, encompass an additional 
150,239 ac (60,800 ha) (BLM et al. 2005, chapter 3, pp. 131, 132), or 
2.8 percent of the range of the Mohave ground squirrel. This area, 
combined with the four designated OHV management areas, constitutes 
about 4.6 percent of the range of the Mohave ground squirrel.
    The BLM has documented other areas not associated with the 
designated management areas where OHV use of designated routes is more 
frequent. The BLM estimates that these high-use areas include about 
107,520 ac (43,512 ha), or 2 percent of the range of the Mohave ground 
squirrel (BLM et al. 2005, chapter 3, p. 133). When combined with the 
management areas and spill-over zones, about 6.6 percent of the 
squirrel's range is intensively used for OHV recreation. One of the 
more extensive high-use areas is the Rand Mountains area. To reduce OHV 
impacts in part of the Rand Mountains area, the BLM expanded the 
Western Rand Mountain

[[Page 62225]]

Area of Critical Environmental Concern (ACEC) from 17,877 ac (7,235 ha) 
to 32,050 ac (12,970 ha), and closed the ACEC to OHV use except for 129 
mi (208 km) of designated open routes, a 90-percent reduction in miles 
of open routes (BLM et al. 2005, chapter 3, p. 8). This resulted in a 
reduction of more than 14,000 acres (5,666 ha) of the high-use area in 
the Rand Mountains.
    Although we are not aware of any estimates, the intensive and 
widespread OHV activity that occurs within the management and high-use 
areas has likely resulted in extensive loss and degradation of 
potential habitat for the squirrel. However