Squirrels of the World

Tamias rufus 335

T. r. simulans—western half of the species’ range. T. r. simu-
lans can be distinguished from T. r. rufi caudus by its paler
sides and the paler ventral surface of its tail.

conservation: IUCN status—least concern. Population
trend—stable. T. rufi caudus is considered at potential risk in
Alberta and British Columbia (Canada), where available
habitat and survey data are limited.

habitat: T. rufi caudus is found in a variety of coniferous
forests, often occurring in open patches or edges where
there is thick ground vegetation. It inhabits various tree
assemblages in diff erent areas, ranging from low- to high-
elevation forests: from ponderosa pine (Pinus ponderosa) for-
ests, to mesic riparian stands, to high-elevation subalpine
stands. The red-tailed chipmunk is typically associated with
signifi cant ground cover, downed woody debris, and thick
brush. Substantial snow cover occurs throughout much of
its range.

natural history: The red-tailed chipmunk is primarily
granivorous-frugivorous, feeding on the seeds and fruits of
a wide variety of trees and shrubs, depending on the habitat.
It mainly forages on the ground and spends a considerable
amount of its time storing food in a larder. Scatter-hoarding
may occur, but this has not been well studied. Like many
other species of Tamia s, T. rufi caudus usually nests under-
ground, beneath rocks, fallen logs, and stumps. Details on
burrow construction are not available, but anecdotal obser-
vations suggest a burrow system similar to that of T. amoe-
nus. Aboveground nests in trees and shrubs have been re-
ported. Nests are usually constructed of grasses and lichens.
The red-tailed chipmunk is diurnal, but it is generally only
active aboveground between April and October. Vocaliza-
tions are reported between mother and off spring but are not

well studied. Mating occurs in late April to mid-May in

lower elevations and latitudes, and from early to late May in

locales where conditions are more severe. Average litter size

varies from 2.5 to 5.2 but is usually between four and six; it

is consistently lower at higher elevations. Gestation is esti-

mated to be 31 days. The young are born as early as late May

and as late as late June, depending on the elevation. Limited

information is available on the demographics and popula-

tion densities of T. rufi caudus. T. rufi caudus is typically found

at elevations above those of T. amoenus and below those of

T. minimus, although altitudinal overlap with the latter may

occur. T. amoenus and T. rufi caudus show similar characteris-

tics, but they remain segregated in most parts of their range.

Limited information on predators and parasites is available.

T. rufi caudus is only known to host one species of fl ea (Cera-

tophyllus ciliatus).

Early comparisons of the morphology (e.g., the cranium

and baculum) of T. rufi caudus suggested that T. r. simulans

and T. r. rufi caudus might be two distinct species. A more

recent analysis of the cytochrome b sequence, in conjunc-

tion with morphological studies of the baculum, supports

the concept that these are two genetically distinct entities,

but it also identifi es a zone of hybridization and therefore an

absence of complete reproductive isolation. These cyto-

chrome b data also reinforce the idea that this species expe-

rienced multiple range contractions, repeated isolation in

numerous Pleistocene refugia, and a recent range extension

to the north. Molecular analyses have documented hybrid-

ization with T. amoenus canicaudis during the Pleistocene but

suggest no recent gene fl ow between the two. The fossil re-

cord suggests that T. rufi caudus may have intermittently

bred with as many as 10 other species in the quadrivittatus

group, with which it is now generally allopatric, with a dif-

ferent bacular morphology.

general references: R. P. Bennett 1999b; Best 1993a;

Good, Demboski, et al. 2003, Good, Hird, et al. 2008; Good

and Sullivan 2001; A. W. Linzey and Hammerson 2008k; Na-

gorsen et al. 1999; Patterson and Heaney 1987; Pearson et al.

2003.

Tamias rufus (Hoff meister and Ellis, 1980)

Hopi Chipmunk

description: Hopi chipmunks are pale orange to cinna-

mon in general tone. The medial dorsal stripe is chestnut;

lateral longitudinal stripes are less apparent; the inter-

spersed light strips are white to grayish. The hips, the

fl anks, and the head are pale gray, and there are large white

Tamias ruf icaudus. Photo courtesy Terry Gray, Moscow, Idaho.