340 Tamias siskiyouTamias siskiyou (A. H. Howell, 1922)
Siskiyou Chipmunk
description: This is a large chipmunk, similar in charac-
teristics to T. ochrogenys and T. senex, but with a distinctive
baculum and baubellum.
size: Female—HB 146.7 mm; T 107.2 mm.
Male—HB 144.5 mm; T 105.0 mm.
Sex not stated—HB 144.4 mm; T 105.2 mm; Mass 75.0 g.
distribution: This species is found in the Siskiyou Moun-
tains, from central Oregon to the coast of northern Califor-
nia (USA).
geographic variation: Like T. senex, T. siskiyou shows
considerable variation between inland and coastal popula-
tions, with each of the two populations showing pelage
characteristics similar to those of T. senex. Two subspecies
are recognized.
T. s. siskiyou—populations within 32 km of the coast in Or-
egon and California (USA). Coastal populations have a
darker tawny pelage and larger cranial features.
T. s. humboldti—all inland populations in Oregon and Cali-
fornia (USA). This form shows a grayish wash with gray-
ish white stripes.
conservation: IUCN status—least concern. Population
trend—stable.habitat: On the coast, this species is associated with mature
forests of redwood (Sequoia sempervirens), Douglas fi r (Pseu-
dotsuga menziesii), western hemlock (Tsuga heterophylla), and
cedar (Chamaecyparis lawsoniana); it is also often associated
with oaks (Quercus) and maples (Acer). Inland populations are
typically found in mature stands of sugar pine (Pinus lamber-
tiana), Jeff rey pine (Pinus jeff reyi), cedar, and Douglas fi r. Sis-
kiyou chipmunks are more abundant in areas with greater
amounts of coarse woody debris, and they are less common
in riparian forests than in adjacent upland stands.natural history: The diet of T. siskiyou includes mostly
seeds and fruits of various trees and shrubs, hypogeous (un-
derground) fungi, and insects. This species is highly arboreal,
but it appears to do well in logged areas with recent regenera-
tion. It is an important dispersal agent of hypogeous fungi in
a variety of forest management regimes. The Siskiyou chip-
munk breeds in early to mid-April and produces three to six
young after a 28–day gestation period. Little is known about
the predators and parasites of T. siskiyou.general references: Jacobs and Luoma 2008; A. N. John-
ston and Anthony 2008; A. W. Linzey and Hammerson
2008m; Piaggio and Spicer 2001.Tamias sonomae (Grinnell, 1915)
Sonoma Chipmunkdescription: Most likely a member of the townsendii
group, the Sonoma chipmunk is usually recognized by its
reddish coloration, larger size, and the white trim on its tail.Tamias siskiyou. Photo courtesy Phillip Colla / Oceanlight.com.