Alternate name: Shadow Chipmunk
Family: Sciuridae, Squirrels view all from this family
Description A large chipmunk, with grayish fur, especially on head, rump, and thighs. Varies from overall dark coloration with obscure back stripes along coast to olive-grayish coloration with conspicuous stripes in Nevada mountains. Usually markings on body relatively indistinct, except dark middle stripe on back. In winter, dark back stripes are black mixed with brown, with middle stripe darkest. In summer, pair of light stripes often tinged with pinkish buff in middle of back. Conspicuous white spot behind ears. Tail pale tawny underneath with indistinct buffy edging. L 9–10 1/4" (229–261 mm); T 3 3/4–4 3/8" (95–112 mm); HF 1 3/8"–1 1/2" (35–38 mm); Wt 2 3/8–3 7/8 oz (67–109 g).
Similar Species Closely related Townsend’s Chipmunk differs primarily in bacular (penis bone) morphology and vocalizations. Yellow-cheeked and Siskiyou chipmunks are difficult to distinguish, but Yellow-cheeked is darker, with more distinct back stripes.
Breeding Mating season begins about 1 month after emergence from hibernation and lasts about 4 weeks. 1 litter per year of 3–5 young.
Habitat Dense, moist brushy areas and coniferous forest with red and white fir trees (Abies magnifica and concolor, respectively), from sea level to 9,500' (2,900 m) elevation in Yosemite National Park.
Range Central Oregon south through n and e California and extreme nw and wc Nevada.
Discussion Allen’s Chipmunk hibernates from November to mid-March. Before hibernation it gains an average of 20 percent of its body weight, depositing layers of fat under the skin and around internal organs. In contrast to other chipmunks, Allen’s is a heavy fungus feeder, but it also eats, in much lower amounts, insects and some vegetative material. This chipmunk was previously considered a subspecies of Townsend’s Chipmunk, but is now recognized as a separate species based on penis-bone morphology and its calls. The calls include an excited bark consisting of three to five notes in a series and a single-syllable chip. These calls also help distinguish Allen’s from the Yellow-cheeked and Siskiyou chipmunks.
