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Tehachapi Pocket Mouse (Perognathus alticolus inexpectatus)
Tehachapi Pocket Mouse
(Perognathus alticolus inexpectatus)
Legal Status
State: Species of Special Concern
Federal: U.S. Forest Service Sensitive, Bureau of Land Management
Sensitive
Critical Habitat: N/A
Recovery Planning: N/A
Notes: Tehachapi pocket mouse (Perognathus alticolus inexpectatus)
was listed in the U.S. Fish and Wildlife Service’s (USFWS’) Animal
Candidate Review for Listing as Endangered or Threatened Species in
1991 and 1994 (59 FR 58804–58836; 59 FR 58982–59028).
Taxonomy
Tehachapi pocket mouse (also called Tehachapi white-eared pocket
mouse) is one of two subspecies of white-eared pocket mouse
currently recognized (Wilson and Reeder 2005). Some authors use the
specific epithet alticola (e.g., Hall 1981; Williams et al. 1993);
however, a current compilation of mammal species of the world
affiliated with the American Society of Mammalogists (Wilson and
Reeder 2005) and the California Department of Fish Game (CDFG)
(2011a) use the epithet alticolus, which is considered the correct
spelling and which is adopted for this species profile. The white-eared
pocket mouse (and its subspecies) is closely related to, and possibly
only subspecifically distinct, from the Great Basin pocket mouse (P.
parvus) (Williams et al. 1993). Tehachapi pocket mouse and whiteeared pocket mouse (P. a. alticolus) occupy geographically distinct
ranges; it has also been theorized that the two are specifically distinct
(Williams et al. 1993). In addition to having a geographical disjunct
range, Tehachapi pocket mouse can be distinguished from the whiteeared pocket mouse by its larger size; darker, more pointed ears; and
square pentagonal interparietal bone (Best 1994; Laabs 2008;
Williams et al. 1993). Descriptions of the species’ physical
characteristics can be found in The Mammals of North America (Hall
1981) and Mammals of North America (Reid 2006).
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Tehachapi Pocket Mouse (Perognathus alticolus inexpectatus)
Distribution
General
The Tehachapi pocket mouse is known from a few scattered localities
in the Tehachapi Mountains, from Tehachapi Pass on the northeast to
the area of Mt. Pinos on the southwest, and around Elizabeth, Hughes,
and Quail lakes on the southeast. It has been recorded between 3,500
and 6,000 feet in elevation (CDFG 2005; Jameson and Peeters 2004).
Of the 16 occurrence records in the California Natural Diversity
Database (CNDDB), 5 are located within the Plan Area, along the
western boundary, while the remaining 11 are located southwest of
this area (Figure SP-M7; CDFG 2011b).
Distribution and Occurrences within the Plan Area
Historical
All five of the CNDDB occurrences within the Plan Area are considered
historic (i.e., pre-1990) and range from 1959 to 1983 (CDFG 2012b).
These occur in Sand Canyon, Oak Creek Canyon, and along Cameron
Creek on private land. Two records are from southwest of Monolith
and south of Tehachapi in the Tehachapi Valley under unknown
ownership (CDFG 2011b). There are also three occurrences of
unknown observation date located northeast of Palmdale at the edge
of the Angeles National Forest and east of Tehachapi Mountain Park
(Figure SP-M7) (Dudek 2011).
Recent
There are no recent (i.e., since 1990) CNDDB occurrences of
Tehachapi pocket mouse in the Plan Area. The most recent occurrence
within the Plan Area was recorded in 1983 (CDFG 2011b).
Natural History
Habitat Requirements
Tehachapi pocket mouse is known to occur in grasslands (both native
and non-native), Joshua tree woodland, pinyon-juniper woodland,
yellow pine woodland, and oak savannah (Williams et al. 1993). It has
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Tehachapi Pocket Mouse (Perognathus alticolus inexpectatus)
been recorded at higher elevations in open pine forests (Huey 1926)
and at lower elevations in chaparral and coastal sage communities
(Best 1994). It has also been detected in fallow fields dominated by
Russian thistle (Salsola kali) (Zeiner et al. 1990). It constructs
burrows in loose, sandy soils (Zeiner et al. 1990). Elevations range
between 3,500 and 6,000 feet. Habitat associations for Tehachapi
pocket mouse are summarized in Table 1.
Table 1. Habitat Associations for Tehachapi Pocket Mouse
Land Cover Type
Grasslands, Joshua tree
woodland, pinyon-juniper
woodland, yellow pine
woodland, oak savannah, open
pine forests, chaparral and
coastal sage communities
Habitat
Designation
Primary
Habitat
Parameters
Loose,
sandy soils;
3,500 to
6,000 feet in
elevation
Supporting
Information
Williams et al.
1993; Huey
1926; Best
1994
Foraging Requirements
Information about the specific foraging requirements of Tehachapi
pocket mouse is not available because no ecological studies have been
conducted. Other pocket mice are nocturnal granivores (seed eaters)
that feed on a variety of grass seeds, but may also feed on leafy plant
material and prey on insects by foraging on open ground and under
shrubs (CDFG 2005; Price and Jenkins 1986; Reichman and Price
1993; Verts and Kirkland 1988). All pocket mice possess fur-lined
cheek pouches that promote collecting and caching of food in scatter
or larder hoards (Reichman and Price 1993), but it is not known
which pattern Tehachapi pocket mouse exhibits.
Reproduction
Pocket mice generally show seasonal reproduction patterns, with
peak activity usually occurring in the spring and summer. For
example, the reproductive period of the congeneric Great Basin
pocket mouse is from March through August (CDFG 2005). Similar to
other pocket mice and the related kangaroo rats (Dipodomys spp.),
reproduction may also be associated with precipitation and
production of herbaceous growth that may support energy
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Tehachapi Pocket Mouse (Perognathus alticolus inexpectatus)
requirements and lactation (e.g., Beatley 1969). Based on studies of
other pocket mice, gestation is likely to last 21 to 28 days, with litter
size ranging from three to eight pups (CDFG 2005). The young are
likely to be weaned within 3 weeks (CDFG 2005). Pocket mice often
show flexible reproductive strategies, with the capacity to produce at
least two litters in good years and with females capable of breeding in
their natal season, while, on the other hand, foregoing reproduction
altogether in poor years (e.g., see Jones 1993 for a detailed discussion
of life history traits). Consistent with relatively low reproductive
output for a rodent,1 pocket mice in general are long-lived, with some
species living 3 to 5 years (Jones 1993).
Spatial Activity
Tehachapi pocket mouse movements, including home range, territory,
and dispersal patterns, are unknown. The home range size of the
congeneric Great Basin pocket mouse has been reported as 0.16 to
0.22 acre in British Columbia, with males having larger home ranges
than females (Howard 1996). Average home range size of Great Basin
pocket mouse from south central Washington was reported as 0.53 to
0.78 acre (Howard 1996), and heteromyids in general do not move far
during foraging bouts (Reichman and Price 1993). It has also been
observed that the home ranges of reproductively active males are
larger than non-reproductively active males (Howard 1996).
In general, there are little dispersal data for pocket mice, but they tend
not to disperse great distances. Jones (1993) cited work
demonstrating that 24% to 30% of long-tailed pocket mouse
(Chaetodipus formosus) made dispersal movements greater than 500
feet; but in another study of the same species, only 5% of the
individuals shifted home ranges; and in a third study, recapture rates
in the same general area were 65% for males and 55% for females
(high recapture rates indicate relatively sedentary behaviors).
Daily surface activity is unknown for Tehachapi pocket mouse, but
pocket mice are primarily nocturnal, with peaks of activity shortly after
dusk and again before dawn (Reichman and Price 1993). The seasonal
timing and temporal patterns of surface activity probably relate to the
Some murid rodent species such as the deer mouse (Peromyscus spp.) have a postpartum estrus that can
result in very high reproduction rates when resource conditions are favorable.
1
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Tehachapi Pocket Mouse (Perognathus alticolus inexpectatus)
availability of food resources, predation risk, energy costs, and other
important activities such as breeding. During the day, pocket mice
remain in their day burrow. During surface activity periods, pocket
mice tend to select microhabitats with shrub or tree canopy cover or
rocky areas for foraging bouts (Reichman and Price 1993).
Aboveground activity patterns may be seasonally variable. Other
pocket mouse species are thought to aestivate during very hot
weather and enter torpor, or dormancy, in cold weather. The related
Great Basin pocket mouse, which inhabits areas with very cold winter
weather, can remain torpid for as long as 8 days with a minimum
body temperature of 2 degrees Celsius (35.6 degrees Fahrenheit)
(Meehan 1977, as cited in French 1993). However, individuals of any
particular pocket mouse species may be active on the surface in most
months in relation to factors such as environmental events, sex- or
age-class, and resource availability (French 1993).
Ecological Relationships
Other than the habitat requirements reported previously, little is
known regarding the ecological relationships important to Tehachapi
pocket mouse. However, substantial work has been conducted on
heteromyid rodent community ecology, including pocket mice
(Perognathus and Chaetodipus spp.) and kangaroo rats. Brown and
Harney (1993) provide a comprehensive overview and draw some
general conclusions:

The diversity and number of coexisting species vary depending
on local conditions and the requirements of constituent species.

Rodent communities are not random, but rather are
determined by interactions among the species, their physical
environment, and interactions with other organisms (e.g., birds
and ants).

Species that coexist tend to exploit different microhabitats or
niches or differ in seasonality of resource exploitation.

Mechanisms that may support diverse communities include
resource
partitioning,
differential
habitat
selection,
independent adaptations, variable foraging efficiency, seed
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Tehachapi Pocket Mouse (Perognathus alticolus inexpectatus)
distribution patterns (e.g., clumped or scattered), resource
availability, predator-mediated coexistence, aggressive
interference, and seasonality.
There are little data for the rodent community structure in areas
occupied by Tehachapi pocket mouse in the Plan Area. A trapping
study conducted on Tejon Ranch west of the Plan Area that
documented Tehachapi pocket mouse also documented several other
rodent species in the general area, including North American
deermouse (Peromyscus maniculatus), brush deermouse (Peromyscus
boylii), western harvest mouse (Reithrodontomys megalotis),
California pocket mouse (Chaetodipus californicus), little pocket
mouse (Perognathus longimembris), agile kangaroo rat (Dipodomys
agilis), desert woodrat (Neotoma lepida), pocket gopher (Thomomys
bottae), and California vole (Microtus californicus) (Jones & Stokes
2008). How the Tehachapi pocket mouse interacts or coexists with
these other species is unknown.
Pocket mice and other heteromyid rodents also modify their
environments (Brown and Harney 1993; Price and Jenkins 1986). They
dig burrows, which moves soils and provides habitat and refugia for
other species, including rodents, reptiles, amphibians, birds, and
invertebrates. Collection, storage, and consumption of seeds by kangaroo
rats, for example, have profound effects on the vegetation structure of
the habitats they occupy (Price and Jenkins 1986). In addition, resource
use by pocket mice and kangaroo rats substantially overlaps with that of
granivorous birds and harvester ants (Pogonomyrmex spp.). While the
co-evolutionary results of such interspecific and intraspecific community
relationships and their relationships to plant communities are not well
understood, it can be concluded that rodents are an important
component of the arid ecosystem.
Pocket mice are also important prey for a variety of predators, with
foxes, coyotes, weasels, owls, and snakes as likely predators of
Tehachapi pocket mouse (Zeiner et al. 1990).
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Tehachapi Pocket Mouse (Perognathus alticolus inexpectatus)
Population Status and Trends
Global: Imperiled to critically imperiled (NatureServe 2011)
State: Same as above (CDFG 2011a)
Within Plan Area: Same as above
The Tehachapi pocket mouse is considered very rare and is in danger
of extinction (CDFG 2005). A survey of a number of historical
Tehachapi pocket mouse locations in the 1980s failed to record any
Tehachapi pocket mouse individuals (Laabs 2008). These surveys
focused on historic localities of ponderosa pine/bracken fern habitat
in the San Bernardino Mountains (Brylski 1998). Some recent data for
the species are available for the Tejon Ranch area west of the Desert
Renewable Energy Conservation Plan project (DRECP) Plan Area,
including several individuals trapped in previously undocumented
locations (Jones & Stokes 2008). However, the overall population status
within its range is unknown.
Threats and Environmental Stressors
Habitat fragmentation and isolation due to increased urbanization
and agricultural intensification appear to be the major threats to this
species. Because the species occurs in isolated, scattered populations,
any natural or human-related event that exacerbates the isolation of
these populations is a serious and immediate threat to this species,
making it vulnerable to local extirpation. Any type of surface
disturbance could be a threat to the Tehachapi pocket mouse.
Livestock grazing could be a threat to the species, resulting in a
reduction in dense shrub cover within its preferred habitat and a
reduction in plant diversity and abundance.
Conservation and Management Activities
There are no known species-specific conservation and management
activities ongoing or planned in the Plan Area. The species'
distribution in the Plan Area is largely within a private inholding
within the San Bernardino National Forest (Brylski 1998). All of the
occurrences within the Plan Area are on private land, including the
California Portland Cement Company, or have unknown ownership
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Tehachapi Pocket Mouse (Perognathus alticolus inexpectatus)
(CDFG 2011b). Recent documented occurrences outside the Plan Area
are also private lands within Tejon Ranch (Jones & Stokes 2008).
Outside of the Plant Area, Tejon Ranch is in the process of
completing a Multiple Species Habitat Conservation Plan for the
Tehachapi Uplands (TU MSHCP). According to the Draft TU MSHCP
published in 2009, 95% of modeled habitat for the Tehachapi pocket
mouse would be conserved and managed in open space (Dudek
2009). A revised Draft TU MSHCP is anticipated to be published for
public review in 2012, and conservation of habitat for the Tehachapi
pocket mouse is expected to be at about the same level as proposed
in the 2009 Draft TU MSHCP.
Data Characterization
There is little species-specific information available on the life history
of Tehachapi pocket mouse; therefore, much of the life history
reported above is for the white-eared and Great Basin pocket mouse,
two other closely related species groups, which the literature assumes
have similar life histories (CDFG 2005; Laabs 2008), as well as other
pocket species. The current distribution of the Tehachapi pocket
mouse in the Plan Area is unknown.
Management and Monitoring Considerations
Additional surveys should be conducted in sagebrush and pinyon
pine-juniper habitats on the northern slopes of the San Bernardino
Mountains, in the Big Bear Basin, and the eastern- and southeasternfacing slopes of the Tehachapi Mountains range. Although the activity
patterns of Tehachapi pocket mouse are unknown, survey efforts
should be focused in late July through August, when activity is likely
to persist after annual recruitment when population numbers are
likely to be highest
The San Bernardino National Forest contains the known localities for
Tehachapi pocket mouse as well as additional potential habitat.
Biologists with the San Bernardino National Forest are aware of the
importance of locating and protecting extant populations, and
should undertake field surveys when resources become available
(Brylski 1998).
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Tehachapi Pocket Mouse (Perognathus alticolus inexpectatus)
Predicted Species Distribution in Plan Area
There are 363,373 acres of modeled suitable habitat for Tehachapi
pocket mouse in the Plan Area. Modeled suitable habitat occurs in the
northwestern portion of the Plan Area, from 3,500 feet to 6,000 feet in
elevation. Modeled suitable habitat includes forest, woodland, scrub
and chaparral, and grassland vegetation communities with sandy
soils. Appendix C includes specific model parameters and a figure
showing the modeled suitable habitat in the Plan Area.
Literature Cited
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Wildlife and Plants; Animal Candidate Review for Listing as
Endangered or Threatened Species.” November 21, 1991.
59 FR 58982–59028. Notice of Review: “Endangered and Threatened
Wildlife and Plants; Animal Candidate Review for Listing as
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Beatley, J.C. 1969. “Dependence of Desert Rodents on Winter Annuals
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Best, T.L. 1994. “Perognathus alticolus.” American Society of
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Brylski, P.V. 1998. “White-eared pocket mouse, Perognathus alticola
alticola.” Draft. In Terrestrial Mammal Species of Special
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Diversity Database (CNDDB). Sacramento, California: CDFG,
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Dudek. 2011. “Species Occurrences–Perognathus alticolus
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Huey, L.M. 1926. “A New Perognathus from the Vicinity of Mount
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575–595. Special Publication No. 10 of the American Society of
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Jones & Stokes. 2008. “Final Draft, Tejon Mountain Village 2007 Small
Mammal Trapping Report.” Prepared for Dudek.
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Price, M.V., and S.H. Jenkins. 1986. “Rodents as Seed Consumers and
Dispersers.” In Seed Dispersal, edited by D.R. Murray. Sydney,
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Zeiner, D.C., W.F. Laudenslayer Jr., K.E. Mayer, and M. White, eds.
1990. California’s Wildlife: Volume III, Mammals. Sacramento,
California: CDFG.
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