Chaetodipus penicillatus
desert pocket mouse

Chaetodipus penicillatus occurs in the southwestern United States and northern Mexico. The northern limit of its range is southern Nevada. It extends southwest into California and the northern Baha Peninsula and northwestern Mexico. Eastward it stretches into the southwesternmost parts of Utah. From southern Nevada and southwestern Utah the range of Chaetodipus penicillatus proceeds southeast into Arizona, through southern New Mexico and southwestern Texas, and into northeastern Mexico (Burt and Grossenheider, 1976; Lee, Riddle, and Lee, 1996; Patton, 1996; Utah Division of Wildlife Resources, 2001).

Chaetodipus penicillatus is found in various arid, open desert environments, usually where the vegetation is rather sparse. These may include desert wash, desert succulent shrub, desert scrub, and alkali desert scrub. It prefers soft alluvian, sandy, or silty soils along stream bottoms, desert washes, and valleys, rather than rocky terrain. These pocket mice live in soils that may be populated by creosote bush, cholla, palo verde, burroweed, mesquite, cacti, and short, sparse grass, as well as in lower edges of alluvial fan with yucca, mesquite, grama, and prickle poppy. (Biota Information System of New Mexico, 2000; Brylski, 2001; Burt and Grossenheimer, 1976)

Chaetodipus penicillatus is a medium-sized pocket mouse. The total length of adults usually does not exceed 180 mm. Coloration is grayish brown to yellowish gray and may be sprinkled with black. The pelage is coarse. This species lacks rump spines but has numerous, elongate rump hairs which are darker dorsally and lighter laterally. There is no lateral line. The underparts of the body and tail are whitish. The tail is heavily crested and is longer than the head and body, with average tail length being 109 mm. The soles of the hind feet are whitish and average hind foot length is 25 mm. The dental formula of Chaetodipus penicillatus is the same as in all heteromyids: I 1/1, C 0/0, P 1/1, M 3/3 X 2 = 20 (Bradley 1997; Burt and Grossenheider, 1976).

Chaetodipus penicillatus has a high population turnover rate, as high as 95% annually. Female desert pocket mice may give birth to one or more litters of young from the early spring to the late summer. Many young females reach sexual maturity early and became pregnant while still in their juvenile pelage (Biota Information System of New Mexico, 2000; Bradley, 1997; Utah Division of Wildlife Resources, 2001).

Few individuals survive more than one year, either in captivity and in the wild (Bradley, 1997).

Chaetodipus penicillatus may be active all year round in some areas, though it is inactive in the winter in southern Arizona. This species is mainly nocturnal. It is aggressively solitary, with a home range of less than 1 acre. Pocket mice can burrow into hard-crusted soils by actually physically chewing their way through the hard portions of the soil. Their burrows, however, are usually excavated in silty, sandy, or gravelly soil and are used for refuges, seed storage, and neonatal care. (Arnold 1942; Brylski, 2001).

Chaetodipus penicillatus forages beneath a canopy of shrubs on sandy or gravely soils. It feeds primarily on seeds of forbs, grasses, and shrubs, although green vegetation and insects may supplement the diet. Seeds of mesquite, creosote bush, and broomweed have been found in the cheek pouches of desert pocket mice. Seeds are also stored in burrows and in dispersed caches throughout their territories. Although there is no direct evidence, this species probably acquires all of the water it needs from its food (Arnold, 1942; Bradley, 1997; Brylski, 2000).

Chaetodipus penicillatus is a granivore, specialized for extreme arid environments. Its competitors include other members of the family Heteromyidae, especially Dipodomys merriami, as well as cricetids (Brylski, 2000).

May play a role in spreading seeds that it feeds on.

Could possibly be a crop or household pest.

Desert pocket mice have exceedingly long renal papillae which function to concentrate the urine and results in a reduction of water loss (Biota Information System of New Mexico, 2000).