Uinta chipmunks, Tamias umbrinus, are discontinously distributed in eight western states, including Nevada, Utah, northern Arizona, eastern California, northwestern Colorado, western and southern Wyoming, eastern Idaho, and southern Montana. Specific mountain ranges where T. umbrinus is found are the Beartooth Mountains in Montana; Uinta and Wasatch Mountains in Utah and Wyoming; Salt River, Wind River, Teton, and Absaroka Mountain ranges in Wyoming; Big Hole Mountains in eastern Idaho; and the Inyo, White, and Sierra Nevada mountains in eastern California and western Nevada. (Harris, et al., 1988; ; Howell, 1929; Johnson, 1943a; Kays and Wilson, 2002; Streubel, 2000; Wilson and Ruff, 1999)
Tamias umbrinus inhabits moderate to high elevation coniferous forests (2000 to 3400 m) typically composed of spruce-fir, Douglas-fir, lodgepole pine, bristlecone, whitebark, ponderosa, limber, foxtail, or drier pinyon pine (Harris, 2004; Streubel, 2000; Montana Fish, Wildlife and Parks, 2005). These chipmunks favor locations near logs and brush in exposed timberline slopes and ridges. The species is primarily arboreal, dwelling in tree cavities where they may sleep or even nest. In addition, individuals of the species may burrow underneath shrubs and rock. (Harris, et al., 1988; Johnson, 1943a; Streubel, 2000)
Tamias umbrinus is a medium-sized species of chipmunk with an average total body length of about 225 mm, and an average mass of 59 g. As in other species of Tamias, males are typically somewhat smaller than females. Five subspecies of T. umbrinus have been documented.
It can be difficult to distinguish Uinta chipmunks from other co-occurring species of chipmunks strictly by sight. However, one diagnostic pelage feature is that the light dorsal stripes are white and surround noticeably-broader brown, rather than black, dorsal stripes as in other species of Tamias. In addition, the medial dorsal stripe, unlike several other species of chipmunk, is not black but instead brownish-black. The outermost dark dorsal stripe is very faint or absent. Tamias umbrinus also possesses a dark-brown tail that is held horizontal while running. The ventral pelage is whitish and the flanks are generally brown or cinnamon in color. The species displays smoky gray-brownish pelage on the head and face regions, with blackish ocular stripes, brown submalar stripes, grayish white postauricular patches, and blackish and grayish white coloration on the anterior and posterior part of the ears, respectively. Winter and summer pelage do not differ significantly.
Like other species of chipmunks, T. umbrinus possesses large, fur-lined, cheek pouches for food storage. This enables individuals to gather and store food as they forage and then transport it back to caches for consumption during winter months. This derived characteristic distinguishes chipmunks from the other members of Scuridae. When danger approaches, chipmunks can run at full speed while still retaining the gathered food in their cheek pouches. (Harris, et al., 1988; Howell, 1929; Montana Fish, Wildlife, and Parks, 2004; Nowak, 1999)
Uinta chipmunks hibernate, and so are heterothermic. An individual's body temperature lowers during hiberation. However, because body temperature remains constant both in hibernation and when individuals are active, they are also homoiothermic. (Nowak, 1999)
Reproductive habits and biology have not been extensively studied in this species, but are likely to be similar to other species of chipmunks in the western region. Once hibernation terminates, nests are built in tree cavities, underground burrows, and even abandoned bird nests. Males may mate with multiple females, and females may also have multiple mates. (Montana Fish, Wildlife, and Parks, 2004; Streubel, 2000)
These animals produce one litter per year. Mating typically occurs after animals come out of hibernation in the spring. Litters of 4 to 5 young are born after a gestation of about one month. The mother may nurse the young for one to two months. Young chimpmunks typically disperse before the winter of the year in which they are born. They are usually reproductively mature by the following spring. (Nowak, 1999)
Data on the reproduction of these animals is scant. However, they are likely to resemble other members of the genus Tamias in regard to parental care. In most chipmunks for which data exist, female parental care seems to be the rule. Males do not participate in the rearing of the young. The female nurses her young for 1 to 2 months. Young typically disperse before winter. (Nowak, 1999; Wilson and Ruff, 1999)
The lifespan of Tamias umbrinus has not been recorded. However, most chipmunks do not live very long. A wild Tamias rufucaudus is reported to have lived for 8 years, and a captive Tamias townsendii lived over 10 years. Uinta chipmunks are likely to have maximum lifespans no greater than this. (Nowak, 1999)
Uinta chipmunks are diurnal and predominately tree-dwelling. Hibernation patterns are similar to other chipmunks in that prolonged sleep is not observed. Instead, chipmunks establish food caches and during winter months enter states of torpor from which they awake every several days to eat from the stored food supply. But T. umbrinus, unlike some other species of chipmunks, consumes extra food during the autumn in addition to storing food in caches. This probably increases the chances of surviving the winter months. Months of hibernation are typically from October to May, but may vary with region and elevation. (Harris, et al., 1988; Montana Fish, Wildlife, and Parks, 2004)
Communication and perception in this species have not been reported. However, it is likely that Uinta chipmunks are like other western chipmunks in these areas. Most chipmunks use a combination of vocalizations and visual cues, such as body posture and tail positioning, in their communication. There is likely to be tactile communication during mating and rearing of young. The role of olfactory cues has not been examined. (Nowak, 1999)
Tamias umbrinus is omnivorous and spends the summer months searching for food in trees, snags, shrubs, and on the ground. In the autumn months, extra food is gathered and stored in underground caches to be used during the winter. Uinta chipmunks feed primarily on fruit, conifer mast, and seeds of maple, juniper, and chokecherry. In addition, fungi obtained by digging are a substantial part of ithe diet. Other items occasionally consumed include pollen, buds, insect larvae, and even bird eggs. (Harris, et al., 1988; Montana Fish, Wildlife, and Parks, 2004)
Because chipmunks carry seeds from their source to caches, it is likely that these animals aid in the dispersal of various seeds. Any burrowing done aids in soil aeration. In addition, these animals provide a host for larval cuterebrid bot flies (Cuterebra fontinella).
There is no direct economic impact of this species on humans. However, indirectly, these chipmunks may be beneficial. Because of their role in seed dispersal, they may help forests to regenerate.
Uinta chipmunks are not known to have negative effects on humans.
Several taxonomic changes have occured that are relevant for T. umbrinus. The genus, Tamias as a whole was formerly known as Eutamias. A sub-species once classified as Eutamius quadrivittatus inyoensis is now placed in T. umbrinus as T. umbrinus inyoensis (Johnson, 1943). It has been suggested that the genus be split into three subgenera, Neotamias, Eutamias, and Tamias, and that both T. umbrinus and T. palmeri be classified as subspecies of Neotamias umbrinus as N. u. umbrinus and N. u. palmeri (Piaggio, 2001).
Uinta chipmunks have been a model for study of territoriality, parapatry, and interspecific competitive exclusion. It has been noted that factors affecting the range of the species include its adaptation to arboreal life and social behavior (see Brown, 1971) or its suceptability to a parasite (Bergstrom, 1992). In the former study, competition with the more aggresive Tamias dorsalis was found to be minimal within the arboreal home range of T. umbrinus, whereas in areas of sparse growth T. dorsalis had a much easier time chasing off Uinta chipmunks. In Bergstrom's study, T. umbrinus was described as the more aggressive species, but showed a higher sensitivity to infestations of larval cuterebrid bot fly common in the lower-elevation territories of two other species. (Bergstrom, 1992; Brown, 1971; Johnson, 1943b; Piaggio and Spicer, 2001)
Annie Danvivat (author), California State Polytechnic University, Pomona, Ryan Long (author), California State Polytechnic University, Pomona, John Demboski (editor, instructor), California State Polytechnic University, Pomona.
Nancy Shefferly (editor), Animal Diversity Web.
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.
uses sound to communicate
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
Referring to an animal that lives in trees; tree-climbing.
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
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
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.
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
an animal that mainly eats all kinds of things, including plants and animals
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
digs and breaks up soil so air and water can get in
places a food item in a special place to be eaten later. Also called "hoarding"
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition. Baltimore and London: The Johns Hopkins University Press.
Piaggio, A., G. Spicer. 2001. Molecular Phylogeny of the Chipmunks Inferred from Mitochondrial Cytochrome b and Cytochrome Oxidase II Gene Sequences. Molecular Phylogenetics and Evolution, Vol. 20, No. 3: 335-350.
Stock, J. 2004. "Bryce Canyon National Park, Mammals" (On-line). Uinta Chipmunk. Accessed October 26, 2005 at http://www.nps.gov/brca/uinta_chipmunk.html.
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