By John Maggirias
Geographic Range
Rock pocket mice occur in rocky habitats in the southwestern United States, from south-central Utah through much of Arizona, New Mexico, Texas (western Sonora, Chihuahua and Trans-Pecos), as well as northwestern Mexico (Wilson and Ruff, 1999; Weckerly et. al., 1985; Weckerly et. al., 1988).
Habitat
Rock pocket mice inhabit desert and are particularly associated with rocky areas. (Wilson and Ruff, 1999). Average home range size is 400 meters (Krebs et al., 1990).
Terrestrial Biomes:
desert or dune 
.
Physical Description
(0.37 to 0.7 oz; avg. 0.54 oz)
Rock pocket mice range from 157 to 188mm in total length, with a tail length from 84 to 112mm. They weigh between 10.5g. and 19.9g. The tails are long and tufted at the tip (Wilson and Ruff, 1999). Their relative size is small in contrast to other members in their genus (Vaughn, 2000). Body size varies regionally (Weckerly et. al., 1988) Pelage is grayish brown on the back with pale orange brown lines on the sides and white underneath. Hairs are coarse with weak "spines" on the rump (Wilson and Ruff, 1999). The bottoms of their hind feet are bare to the heels (Wilson and Ruff, 1999). Dental formula is 1/1 0/0 1/1 3/3=20 and cheek teeth of are ever growing (Vaughn, 2000). Sexual dimorphism is observed, with males being larger overall and in certain morphological features such as mastoid width, nasal length, and mandible length (Wilson and Ruff, 1999; Weckerly et al., 1988).
Some key physical features:
endothermic ; bilateral symmetry .
Reproduction
The breeding season begins in February or March and progresses into July. Litter size varies from three to six (Wilson and Ruff, 1999). Similar to other species of pocket mice, rock pocket mice live for a maximum of three years (Paulson, 1988). Van de Graff (1975) observed that males tend to be in reproductive condition for longer periods each year than females. In southeastern Arizona all males captured from February until September were fertile. Females are reproductively active from February until the end of July. Males in reproductive condition averaged 2.3g. heavier than those that were not (Van de Graff, 1975). During prolonged droughts reproduction is often delayed and survivorship of young is 7.3% (Paulson, 1988).
Key reproductive features:
gonochoric/gonochoristic/dioecious (sexes separate); sexual .
Behavior
Rock pocket mice are nocturnal. During colder periods they become torpid but may remain active for a period of two hours when temperatures are below freezing. They accomplish this by altering basal metabolic rate to be higher in colder temperatures (Wilson and Ruff, 1999).
Key behaviors:
motile .
Food Habits
Rock pocket mice are granivorous, feeding on a variety of seeds depending on availability (Rebar, 1995; Wilson and Ruff, 1999). They are capable of collecting seeds in fur-lined cheek pouches. Cheek pouch volume is directly proportional to body size (Vander-Wall et al., 1998).
Economic Importance for Humans: Negative
No literature available to identify negative economic importance to humans.
Economic Importance for Humans: Positive
No literature available to identify positive economic importance to humans.
Conservation Status
IUCN Red List: [link]:
Lower Risk - Least Concern.
US Federal List: [link]:
No special status.
CITES: [link]:
No special status.
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For More Information
Find Chaetodipus intermedius information at
Contributors
John Maggirias (author), University of Toronto.
