Squirrels of the World

Tamias sp e ciosus 341

size: Female—HB 138.3 mm; T 106.6 mm.
Male—HB 134.3 mm; T 106.4 mm.
Sex not stated—HB 133.2 mm; T 111.6 mm; Mass 70.0 g.

distribution: T. sonomae occurs in northwestern Califor-
nia (USA), from Siskiyou County south to San Francisco
Bay. It is found from the upper Sonoran to transition life
zones, below an elevation of 1800 m.

geographic variation: Two subspecies are recognized.

T. s. sonomae—throughout the species’ range. T. s. sonomae is
larger than T. s. alleni.
T. s. alleni—only in the extreme southwestern portion of the
species’ range, near San Francisco Bay in California
(USA). The head and the venter of T. s. alleni are darker in
coloration.

conservation: IUCN status—least concern. Population
trend—stable.

habitat: T. sonomae is found in open stands of redwood
(Sequoia sempervirens), drier low-elevation stands of ponder-
osa pine (Pinus ponderosa), and scrub oak (Quercus) habitat,
such as chaparral; it also occurs along streams or open
brushy fi elds, and in stands of digger pine (Pinus sabiniana),
white fi r (Abies concolor), or red fi r (A. magnifi ca).

natural history: Little information is reported on the
feeding habits of the Sonoma chipmunk, but it is assumed to

consume conifer seeds, the acorns of scrub oaks (Quercus),

and the seeds and leaves of other chaparral plants. The So-

noma chipmunk breeds once per year, usually in the spring,

but often earlier at sea level. Litters range in size from three

to fi ve young. After weaning, females often remain at the

nest while males disperse. This results in female kin clusters,

and it has been hypothesized that this facilitates the evo-

lution of alarm calling (via kin selection), as is reported for

T. striatus. Females produce alarm calls more often than

males. The only observed predator for T. sonomae is the Red-

Ta i led Hawk (Buteo jamaicensis). Parasites include two lice

(Hoplopleura arboricola and Neohaematopinus pacifi cus) and

the larval or nymph stages of three tick species (Dermacentor

occidentalis, Ixodes pacifi cus, and I. spinipalpis).

general references: Best 1993b; Burke da Silva et al.

2002; Casher et al. 2002; R. M. Davis et al. 2008; A. W. Linzey

and Hammerson 2008n.

Tamias sp e ciosus Merriam, 1890

Lodgepole Chipmunk

description: This is a midsized member of the genus. The

dorsal stripes are distinct alternating bands of light and dark

that extend through the eye and across the side of the face

to the nose. The sides are cinnamon to yellowish orange or

light brown in color. The skull is broad, and the rostrum is

short and narrow at the anterior end. The tail is dark, espe-

cially a short subterminal portion of the ventral surface.

size: Female—HB 127.1 mm; T 88.5 mm; Mass 62.7 g.

Male—HB 122.2 mm; T 86.8 mm; Mass 56.8 g.

Sex not stated—HB 124.4 mm; T 94.8 mm; Mass 59.2 g.

Tamias sonomae. Photo courtesy David Mclelland.