The red-tailed chipmunk is found in the central Rocky Mountain region of the United States in northwestern Montana, northern Idaho and northeastern Washington. In Canada, the range of -Tamias ruficaudus- just touches extreme southwestern Alberta and the East Kootenay valley of southern British Columbia. (Banfield, 1974; Nowak, 1999)
The red-tailed chipmunk inhabits dense coniferous forests. Its numbers are greatest where shrubby growth is rich. These conditions typically occur in forest openings or edges. They can be found in forests of -Tsuga heterophylla- (western hemlock), -Thuja plicata- (western red cedar), -Pseudotsuga menziesii- (Douglas fir), and -Picea englemanni- (Englemann spruce). They are limited by open -Pinus ponderosa- (Ponderosa pine) on the western edge of their range. -T. ruficaudus- occupies bunches of stunted pine and spruce trees, and -Rhododendron- (mountain rhododendron) and -Vaccinium- (blueberry bushes) on the margins of meadows. They occur in Washington in mixed second-growth forests of -Pinus contorta- (lodgepole pine), -Larix occidentalis- (western larch), Englemann spruce, Douglas fir, -Abies grandis- (grand fir), and -Populus tremuloides- (aspen).
In northern Idaho, the red-tailed chipmunk is considered to be the most widely distributed and common chipmunk. They are plentiful higher in the mountains. In the Ponderosa pine zone, they can be found in openings with great amounts of light where boulders and low brush are present. This usually occurs along older roadways and at the lower edge of foothills. -T. ruficaudus- can be found near fallen logs and brush piles in the Canadian zone.
This species of chipmunk typically resides in burrows and on the ground, but can climb trees and bushes at times. They look for protection in old logs, crevices among rocks, and their burrows. (Best, 1993; Nowak, 1999)
The red-tailed chipmunk is darker colored and larger than most chipmunks. The appearance of this chipmunk is generally similar to that of Tamias minimus (least chipmunk) and the yellow pine chipmunk. However, the red-tailed is larger and colored more brightly. In general, the pelage is rufous on the shoulders and sides, with this color fading out towards the hips. The back has a deep orange-brown tone and the rump is a shade of gray. The feet are a light brown color and the underparts are ivory. The color of the tail is rufous on the dorsal side with the ventral side a bright orange or brick red. The tail also has a black band and the tips of the hairs are yellowish. The ears are black. T. ruficaudus has five dark stripes that range from black to fuscous. The central dark stripe runs between the ears to the tail. The four pale stripes are grayish to white. The forehead is chocolate brown and the cheeks are characterized by two milky stripes separated by three brown stripes. The eye stripe is black and the stripe below the eye is brownish.
The winter pelage of T.ruficaudus is soft, dense and slightly wooly. There are two molts each year, one occurring in the spring and a second molt in the early autumn. The summer pelage differs from the winter in that it is more brightly colored.
The dental formula of the red-tailed chipmunk is 1/1 0/0 2/1 3/3=22. The skull has a short rostrum and is ovate. The postorbital processes are slender and long. The subgenus Neotamias, to which the red-tailed chipmunk belongs, is differentiated from the subgenus Tamias in that Neotamias has two premolars on each side of the upper jaw and Tamias only has one.
The red-tailed chipmunk is sexually dimorphic. Females are approximately 3% larger than males in head length and body. Males also have narrower skulls than females.
(Banfield, 1974; Best, 1993; Nowak, 1999; Smith, 1993)
Mating in -T. ruficaudus- can occur from late February to early July but usually takes place in April or May. Pregnancy rates vary among age groups. Females that were 10 to 16 months of age were pregnant less often than older females. The overall rate of pregnancy for the population was 68 to 83% where females 10 to 16 months of age were not considered. There is only one breeding season per year, unless a litter is lost. In this case the female can enter estrus again and bear a second litter. The gestation period is 28 to 36 days. Embryos of 25 mm in head-rump length are full term. The litter size is usually three to eight young and sexual maturity is reached within the first year of life. The record of longevity in the wild for chipmunks was achieved by -T.ruficaudus-. This particular animal lived for eight years. However, fewer than 10% of the individuals survive more than 64 months. (Best, 1993; Nowak, 1999)
When the weather begins to turn cold, the number of active -T. ruficaudus- decreases. They remain in their burrows during colder days from mid-November to late March. They can become active as early as March 29 and remain active as late as December 4. However, the major activity season is April to October. Males become active earlier than females.
An interesting behavior exhibited by red-tailed chipmunks is sandbathing. They roll from side to side in the sand and even become half-buried.
Most foraging is done on the forest floor during the spring. They may forage a distance of 45 to 60 mm within three to four minutes. Foraging in shrubs increases in the summer. In the autumn, trees are foraged more than during any other season.
-T. ruficaudus- is more arboreal than other chipmunks; in fact, they perform much of their foraging in trees.
Red-tailed chipmunks may have nest holes in living or dead trees. A dead fir of 5.4 m in height can house up to six red-tailed chipmunks. They also may build an underground lodge in the center of their home range. This lodge is often located in shrubbery or in trees, but it can also be unexposed.
The home ranges of -T. ruficaudus- are about 0.10 hectares, or about 1.6 ha for males and .93 ha for females. These ranges overlap, and the area around a burrow is defended. These chipmunks stake out an area for their activities and roaming. This area is defended against members of the same species.
The two main categories of vocalization are alarm calls, including a chip, chuck, chippering, or even a trill or whistle; and courtship vocalizations, which sounded harsh.
One of the most notable behaviors of the species is hoarding. This species is a systematic hoarder. A chipmunk approaches a food item, picks it up, runs with it, and then caches it, usually in a hole it digs. This hole is filled up after the food is buried. The area is raked over afterwards. (Banfield, 1974; Best, 1993; Carrington, 1963; Krapp, 1990; Nowak, 1999)
Red-tailed chipmunks gather dry food that they carry in their cheek pouches and store underground. They feed at discrete times during daylight hours. These animals become torpid in the winter and feed from time to time upon their larder. Their diet includes the seeds of fir trees, honeysuckles, locusts, and cranberries. In Idaho, they have also been observed feeding upon the seeds of Douglas knotweed. In Montana, the chipmunk eats the fruits and seeds of nine-bark, wild rose, Ponderosa pine, snow brush, serviceberry, big whortleberry, buckbrush, knotweed, grass, huckleberry, mountain maple, and bull thistle. They also eat the leaves and flowers of the dandelion, arnica, currant, balsam-root, glacier lilly, oyster plant, willow herb, and tarweed. -T. ruficaudus- has been caught in the wild with steel traps baited with meat. (Best, 1993; Nowak, 1999)
The red-tailed chipmunk can be tamed quite easily for the purposes of laboratory study. (Best, 1993)
Red-tailed chipmunks typically favor brush-covered or rugged land. However, sometimes they occur near agricultural crops. When this happens, they can do damage by eating planted seed, young forest plantings, and even fruit trees. (Nowak, 1999)
Generally, -Tamias ruficaudus- are abundant in most areas. They seem to have avoided the fate of some of their close relatives, -Tamias palmeri-, -Tamias minimus atristriatus-, and -Tamias quadrivittatus australis-, which have all appeared on the IUCN list or have become extinct. (Nowak, 1999)
Two subspecies of Tamias ruficaudus are recognized, T. r. ruficaudus and T. r. simulans. These subspecies are differentiated based on their cranial and bacular morphology. Nevertheless, evidence of interbreeding among these taxa has been discovered, and there appears to be substantial gene flow throughout the species.
The name Tamias comes from the Greek tamias meaning storer or distributor. Ruficaudus is from the Latin rufus meaning reddish, and cauda meaning tail. Other names include rufous-tailed and Coeur d'Alene chipmunk. (Best, 1993; MSW Scientific Names)
Kristi Jacques (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
1999. "Convention of International Trade in Endangered Species of Wild Flora and Fauna" (On-line). Accessed December 12, 1999 at http://www.wcmc.org.uk.
1993. "MSW Scientific Names" (On-line). Accessed December 12, 1999 at http://www.nmnh.si.edu/cgi-bin/wdb/msw/names.
Banfield, A. 1974. The Mammals of Canada. Toronto: University of Toronto Press.
Best, T. November 15, 1993. Tamias ruficaudus. Pp. 1-7 in Mammalian Species. The American Society of Mammalogists.
Carrington, R. 1963. The Mammals. New York: Time Incorporated.
Krapp, F. 1990. Squirrel-like Rodents. Pp. 63 in Grzimek's Encyclopedia of Mammals. New York: McGraw-Hill Publishing Company.
Levensohn, H., R. Hoffmann, C. Nadler, L. Deutsch, S. Freeman.. 1985. Systematics of the holarctic chipmunks Tamias. Journal of Mammalogy, 66(2): 219-242.
Nowak, R. 1999. Walker's Mammals of the World. Baltimore and London: Johns Hopkins University Press.
Smith, H. 1993. Alberta Mammals: An Atlas and Guide. Edmonton, Alberta: Provincial Museum of Alberta.