Brownish or grayish above to buff or tawny on sides; white below. Tail distinctly bicolored, hairy, equal to or longer than head and body, with slightly tufted tip. Ankles dusky. Large ears. L 7 1/8–9 3/8" (180–238 mm); T 3 5/8 –4 3/4" (91–123 mm); HF 3/4–1" (20–26 mm); E 3/4" (16–20 mm); Wt 3/4 –1 1/4 oz (22–36 g).
Deer and White-footed mice in range of this species have tails shorter than head and body. Pinyon and Northern Rock mice have longer ears. Cactus and Canyon mice have smaller ears.
Breeds throughout year, producing several litters of 1–6 young. First-year females may produce litters late in the year.
Varied. Arid to semiarid brushland, especially in rocky areas; abundant at times in oaks, junipers, pinyons.
Extreme s Oregon south through California and east to w and s Nevada, Utah, Arizona, Colorado, New Mexico, w Texas, and w Oklahoma.
A skilled climber, the Brush Mouse clambers about on cliffs and in trees and will often run up trees to avoid predators. It frequently occupies higher portions of the habitat, while other species, such as deer mice or cotton rats, occupy the lower areas. This mouse uses its long tail as a prop when climbing and as a balancing organ when on a limb. It will not jump more than about 2 feet (60 cm). Foods include conifer seeds, acorns, berries, and insects. The Brush Mouse eats cactus fruit extensively when this food is in season. In Kansas it eats acorns especially heavily. It also eats wheat, corn, and oat seeds when they are available. In California this species feeds heavily on acorns in winter and manzanita berries in summer, with cutworms and other insects making up half or more of its diet in spring. The animal stores seeds in a crevice or hollow, but apparently not in the nest. Brush Mice commonly associate with woodrats and have been found in their nests. Owls, coyotes, hawks, snakes, and many other animals undoubtedly prey on this species.