Montana Field Guide

The Uinta Chipmunk is a medium-sized chipmunk, with moderately distinct dorsal stripes and generally warm brownish pelage on the flanks, shoulders, and head. In some regions they may be difficult to distinguish from other chipmunk species by sight. The outermost stripe is white bordered by brown, not black. It is more likely to be seen in trees than other chipmunks sharing its range (Bergstrom 1999). Adults may attain the following body measurements: total length 200 to 243 millimeters; tail length 90 to 115 millimeters; hind foot 30 to 35 millimeters; ear 16 to 19 millimeters; weight 55 to 80 grams. Sexes are similar in size (Clark and Stromberg 1987). There are 22 teeth in the skull (dental formula: I 1/1, C 0/0, P 2/1, M 3/3), and the skull is more than 34 millimeters in length.

In Montana, the Uinta Chipmunk is sympatric only with the Least and Yellow-pine Chipmunks, and is larger than both. The outermost light dorsal stripe is white (not grayish or yellowish) and bordered by brown, not black as with other species; similarly all of the central dark dorsal stripes are brownish-black, not black as in the other Montana chipmunks. Unlike the Least Chipmunk, it tends to hold its tail horizontally rather than vertically when running, and is generally darker brownish rather than washed grayish or yellowish. Unlike the Yellow-pine Chipmunk, the belly is whitish. Gray-brown coloration on the face and head separate it from the Red-tailed Chipmunk, which is reddish in those body areas and does not occupy the same part of the state (Foresman 2012).

No information is available on Uinta Chipmunk movements or home range size for Montana. The species is known elsewhere to be non-migratory; apparently only local movements are made. In Colorado, minimum convex polygon home ranges of radio-tracked individuals were 1.87 to 5.12 hectares, and home range lengths were 179 to 457 meters (Bergstrom 1988).

Habitat use in Montana is unstudied and poorly described. The Uinta Chipmunk is found at high elevation in Carbon and southeastern Park Counties in subalpine forest and at treeline in krummholz vegetation, presumably subalpine fir-Engelmann spruce-whitebark pine (Pattie and Verbeek 1967).

Elsewhere, Uinta Chipmunks are known to frequent coniferous forests at moderate to high elevations (to upper treeline). In Wyoming, they are reported occupying spruce-fir forest, lodgepole pine-Douglas-fir forest, and ponderosa pine forest (Clark and Stromberg 1987). In Colorado, they have been reported in ponderosa pine-Douglas-fir forest (Bergstrom 1988). In more southern regions of the global range, they are most often associated with ponderosa pine habitats, but also are found in drier pinyon pine-juniper woodlands; in California and Nevada they also are found in bristlecone pine woodlands (Bergstrom 1999). They often are found near logs and brush in open areas and at forest edges, sometimes in forest with a closed canopy but an open understory. They excavate burrows beneath rocks and shrubs, but also are arboreal to some degree, spending a fair amount of time in trees and sometimes sleeping and nesting in tree cavities.

Uinta Chipmunks feed primarily on conifer mast (including ponderosa pine and Douglas-fir) and shrub seeds (including juniper, maple, and chokecherry), supplementing these with buds, pollen, and fruits. A relatively large part of the diet is fungi, some of which is acquired through digging. Occasionally they eat insect larvae, birds' eggs, and carrion. In fall, seeds are stored in caches and provide the bulk of the winter food supply (Bergstrom 1999). The diet in Montana has not been reported or studied.

The ecology and life history of the Uinta Chipmunk have not been studied in detail, but apparently are quite similar to that of the Least Chipmunk (Tamias minimus), including activity cycles, foraging behavior, hibernation, predators, and vocalizations (Bergstrom 1999). They are active only during the day. Some individuals in Colorado spend a great deal of time in trees, and are very tree-squirrel-like in food habits and arboreality. Both sexes often sleep and nest in trees. They do not hibernate as deeply as ground squirrels and live through the winter on stored food rather than stored fat. Time of spring emergence from, and fall entry into, hibernation has not been studied in detail; hibernation probably occurs during October to May in Wyoming (Clark and Stromberg 1987).

In Montana, individuals are still active at alpine treeline in early August (Pattie and Verbeek 1967).
Predators have not been reported, but undoubtedly include certain mammals and birds. Uinta Chipmunks are more aggressive in territorial defense than other chipmunk species; they are sympatric with Least Chipmunks and Yellow-pine Chipmunks (Tamias amoenus) in some parts of the range, but segregate by smaller-scale habitat differences. In Montana, the Uinta Chipmunk appears to be the ecological counterpart to the Red-tailed Chipmunk (Tamias ruficaudus) that occupies the majority of the western mountains (Foresman 2012).

Vital statistics and population trends are mostly unknown.

The reproductive biology of Uinta Chipmunk has not been studied in Montana and is largely unstudied elsewhere. It is probably similar to other western chipmunks. Mating likely occurs shortly after spring emergence from hibernation, resulting in the production of a single litter of 4 to 5 altricial young following a gestation period of approximately 30 days. Litters are raised in nests built in burrows, tree cavities, and abandoned bird nests that have had roofs added (Bergstrom 1999). In northwestern Wyoming, lactation has been observed in early and mid-July (Clark and Stromberg 1987). Young are weaned and foraging on their own in mid-July or August. Females probably reach reproductive maturity the summer after birth. Longevity has not been reported.

In Montana, the Uinta Chipmunk is at the extreme northern limit of the global distribution and is considered locally restricted and not abundant (Foresman 2012). No special management activities to conserve this species are in practice, nor are any recognized at this time. Occupancy of high elevation forest in or near designated Wilderness Areas largely buffers this species from timber harvest pressures.