Squirrels of the World

Tamias minimus 325

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

habitat: Merriam’s chipmunk is found only in the upper
Sonoran and transition life zones, from sea level to 2940 m
in elevation. Although T. merriami occurs in a wide range
of habitats, it usually occupies shrubby chaparral vegeta-
tion often associated with pine (Pinus) and oak (Quercus).
Downed woody debris and rocks are also important habi-
tat components.

natural history: Merriam’s chipmunk has a broad diet,
including the seeds, fruits, and nuts of numerous plant spe-
cies; insects; and other animal material when available.
Acorns and conifer seeds appear to be the mainstay of its
diet, and in some years acorns may occur in the diet year-
round. This species may be important for forest regenera-
tion, although detailed studies on its caching behavior are
not available. Drought conditions reduce this chipmunk’s
densit ies, probably a s a result of decrea sed food supply. Mer-
riam’s chipmunk is usually active throughout the year; it
hibernates only at the highest elevations within its range. T.
merriami is diurnal, showing peaks of activity in the morn-
ing and afternoon, separated by a midday rest. Both under-
ground nests and tree cavities are used for shelter, although
the latter appear to be preferred for rearing young. Shelters
used by T. merriami are often prepared by other species, such
as woodpeckers, pocket gophers (Thomomys), and ground
squirrels. The tail of T. merriami, the longest and bushiest
within the Tamia s species, appears to be used for thermo-
regulat ion as wel l as in ba la nce. Ta il leng t h is negat ively cor-
related with elevation. When water is limited, T. merriami
appears to show behavioral and physiological adjustments
to reduce water loss.

general references: Best and Granai 1994a; R. M. Davis
et al. 2008; A. W. Linzey, Timm, et al. 2008b.

Tamias minimus Bachman, 1839

Least Chipmunk

description: As one of the smaller members of the genus,
T. minimus is nearly indistinguishable from several similar-
sized congeners within its range. However, subtle diff er-
ences in cranial morphology or pelage coloration allow it to
be separated out from similar species in each part of its
range. The ventral surface of the tail varies from reddish
yellow to brown.

size: Female—HB 114.2 mm; T 82.4 mm; Mass 46.4 g.

Male—HB 109.3 mm; T 80.3 mm; Mass 43.7 g.

Sex not stated—HB 106.0 mm; T 84.9 mm; Mass 50.5 g.

distribution: T. minimus ranges from central Yukon east

to western Québec (Canada) and Michigan (USA) and south

through the Cascade Range, the Sierra Nevada, and the

Rocky Mountains in the western states, with isolated popu-

lations in Arizona and southern New Mexico (USA).

geographic variation: Twenty-one subspecies are rec-

ognized in this geographically diverse species.

T. m. minimus—“Found on plains and Sonoran plateaus in

Wyoming, northeastern Utah, and Northwestern Colo-

rado” (Anthony). The general color is dull gray, with the

upperparts grizzled gray and buff , and the underparts

white. The hairs on the ventral surface of the tail are

rufous, banded with black and edged with buff y.

T. m. arizonensis—type locality is the Prieto Plateau at the

south end of the Blue Range, Greenlee County, Arizona

(USA). This form is similar in color to T. m. consobrinus,

but T. m. arizonensis is grayer, with less tawny. The shoul-

ders are washed with pale smoke gray. The tail is bright

tawny on the ventral surface.

T. m. atristriatus—Peñasco, New Mexico (USA). The sides are

grayish fulvous, and the underparts are yellowish. The

dorsal light stripes are rusty gray and buff y white. Al-

though similar to T. m. operarius, this form is slightly

larger, darker, and duller in color.