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ROCK POCKET MOUSE
Chaetodipius intermedius Merriam 1889

Order Rodentia : Family Heteromyidae

DESCRIPTION. A medium-sized, long-tailed pocket mouse; pelage rather harsh, with weak spines on rump; sole of hind foot naked to heel; tail longer than head and body, crested and distinctly tufted; upperparts drab, with strong admixture of black on back and rump; lateral line pale fawn, narrow; tail dusky above, white below; underparts white. Similar externally to C. eremicus, but hind foot usually smaller, upperparts much darker, tail with smaller scales and narrower annulations. Dental formula: I 1/1, C 0/0, Pm 1/1, M 3/3 × 2 = 20. Averages for external measurements: total length, 180 mm; tail, 103 mm; hind foot, 23 mm. Weight, 12–18 g.

Chaetodipus intermedius

DISTRIBUTION. Known only from the western portion of the Trans-Pecos region in El Paso, Hudspeth, Culberson, Jeff Davis, Presidio, Reeves, and Brewster counties.

Distribution of Chaetodipus intermedius

SUBSPECIES. Chaetodipus i. intermedius.

HABITS. This species mainly inhabits areas with large rock outcroppings and boulders. At the eastern base of the Guadalupe Mountains, in western Texas, they have been found inhabiting rocky canyons, and in the Wylie Mountains they live among large boulders. Occasionally, they may be found on shrubby desert slopes on pebbly soils, rarely on silt soils. Vernon Bailey reported finding them on sandy soils among rocks. Apparently they rarely occur in areas of loose, alluvial, and windborne sands.

Their burrows are small, inconspicuous, and located close to or under rocks. Burrows often are closed during the daytime. Tiny trails lead away from them to feeding places among the plants.

The rock pocket mouse is strictly nocturnal; at night it forages primarily for the seeds of herbaceous plants. Seeds are cached for consumption during periods of environmental stress. In addition, caching may help this pocket mouse maintain a diverse diet, and the growth of fungi on cached seeds may increase their nutritional value.

Judging from the meager data, breeding begins in February or March and continues for several months. Pregnant females have been captured in May–July. The litter varies from three to six. Nearly half-grown young in juvenile pelage have been taken in April, May, June, and August. There is no documentation of this pocket mouse's entering seasonal dormancy, and it probably is active year-round.

They seldom pose a conflict to human interests.

POPULATION STATUS. Common. The rock pocket mouse is common throughout the Trans-Pecos region.

CONSERVATION STATUS. The IUCN lists the rock pocket mouse as a species of least concern, and it does not appear on the federal or state lists of concerned species. It does not appear to face any serious threats at this time.

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From The Mammals of Texas, Seventh Edition by David J. Schmidly and Robert D. Bradley, copyright © 1994, 2004, 2016.  Courtesy of the University of Texas Press.

Natural Science Research Laboratory