Perognathus parvus
Great Basin pocket mouse

This pocket mouse can be found in the Great Basin from South British Columbia (Canada), south to eastern California and east to southeast Wyoming and northwest Arizona (Wilson 1993).

The Great Basin pocket mouse can be found in shrub/grassland communities of sagebrush, shadscale, greasewood, mountain mahogany, and bitterbrush. Habitats dominated with shrub are useful in vegetative cover, while also providing better and more diverse food resources (Bushey 1987).

Head and body length: 60-90 mm Tail length: 45-100 mm

The upper parts of its body are a pinkish buff color, which is thinly to heavily overlaid with a blackish color, while the underparts vary from white to buffy. The soft coat of this mouse has no bristles. One molt takes place in late summer. The soles of its hind feet are hairy, and the tail is long and bicolored (Hall 1981).

Its hind limbs are about the same length of its forelimbs, and the Great Basin pocket mouse moves about on all four legs. While the hind legs provide support, the forefeet dig with claws through sand to find seeds (Nowak 1991). These seeds are then placed in fur-lined external cheek pouches, which open alongside its mouth (Britannica 1997).

From about late April to early August, males are in breeding condition, while females show the first sign of estrus in April. Early June is probably when breeding occurs at its peak. Pregnancies then occur from May to July. Gestation lasts 21 to 25 days. When there is an abundance of food, females have an average of two litters per year. Some have even been found to have three litters. Otherwise, an average of 1.1 litters is produced. Litters vary from three to eight mice. Juveniles born early in the season are able to breed themselves by late summer (Nowak 1991).

Most individuals remain underground from December to March, but for the rest of the year they emerge for an average of sixty days to ninety days, depending on the abundance of food. They return to their burrows from late summer to early fall (Bushey 1987). Great Basin pocket mice are nocturnal and stay in their burrows during the day. The entrances of the burrows, usually hidden under shrubs, are covered with earth in order to maintain a low temperature and high humidity (Nowak 1991).

It has been found that the peak population in south-central Washington during autumn was an average of 320 individuals in a 2.7 ha. study area. The home range was 1,560-4,005 square meters for males and 508-2,301 square meters for females (Nowak 1991).

Its diet consists mostly of seeds of forbs, grasses and shrubs. Along with green vegetation, insects are eaten particularly when they are abundant (Grzimek 1990).

Great Basin pocket mice are common and not endangered (Grzimek 1990). Because they are able to retreat to underground burrows, these mice are not in much immediate danger from fires in sagebrush and bunch grass habitats. However, fires reduce food resources and vegetative cover, making the mice more susceptible to predators (Bushey 1987).

The family name of Heteromyidae comes from the Greek "heteros", meaning "the other, different from the usual," while the genus name of Perognathus comes from two words in Greek. "Pera" means "a pouch, a pocket," and "gnathos" is "the jaw, the mouth" (Gotch 1979).