Tamias minimus - Least Chipmunk

Physical Description:

The least chipmunk, Tamias minimus, is the smallest squirrel in the Great Lakes Basin.  It has a total length of 185-222 mm, tail length of 80-100 mm, hind foot length of 28-35 mm, ear height of 13-18 mm, and weight of 42-53 g (Kurta 1995).  Tamias minimus has five dark brown or black stripes running down its back, with the middle one reaching from the crown of its head to the base of its tail.  Between the dark stripes, run lighter colored stripes with the outer ones being white and the inner ones, adjacent to the median dark stripe, a light brown.  It also has four whitish stripes on its face, one above and one below each eye.  The sides of its body are orangish brown, its shoulders a bright rufous, its belly grayish white, and its tail pale brown with the hairs tipped black (Hamilton and Whitaker 1979).  Tamias minimus looks similar to Tamias striatus, the eastern chipmunk, but T. striatus is larger, has a distinct reddish brown patch on its rump, and its stripes on its back don’t extend to the base of its tail.  T. striatus also only has four upper cheek teeth on each side compared to T. minimus’s five (Kurta 1995).

Distribution:

Tamias minimus is distributed throughout central and western North America, including the Rocky mountain region and the western Great Plains of the United States, central and western Canada, and parts of Wisconsin, Minnesota and Michigan. It occupies the widest geographic and altitudinal range of any chipmunk.

In Wisconsin it is found in the north and south-central counties (Hamilton and Whitaker 1979), however, there is evidence that its distribution may be retreating northward (Jackson 1961, Long 1970).  In 1970, Long reported that T. minimus was found only as far south as extreme northern Marathon County with none in Portage or Wood Counties.  This change in T. minimus’s distribution may be due to the immigration of T. striatus into the area (Jackson 1961).

Ontogeny and Reproduction:

Least chipmunks mate in April.  One month later, they bear a single litter of four to seven naked young, each weighing about 2.2 g (Hamilton and Whitaker 1979, Kurta 1995).  If the first litter fails due to predation, the female may try to have another litter that same season (Kurta 1995).  Gestation takes about 30 days and lactation lasts an additional 60 days.  The young remain with the parent for at least six weeks (Hamilton and Whitaker 1979).  The offspring wait to mate until the following year when they are about 10 months old (Kurta 1995).

Ecology and Behavior:

Least chipmunks are found in a wide variety of different habitat types, including forests, forest edges, pastureland, lake shorelines, rocky cliffs, and river bluffs (Hamilton and Whitaker 1995).  They are adapted to living in exposed areas and avoid dense tree cover, especially thick evergreen forests (Forbes 1966).  Even though they are commonly found on the ground, they are expert climbers and will spend much of their time in trees and shrubs, up to heights of 9 m, foraging for food and sunning themselves during the cool of early morning (Hamilton and Whitaker 1979, Kurta 1995).  They will even make nests and rear their young high in trees in a similar fashion to true tree squirrels (Hamilton and Whitaker 1979). They are territorial and will defend their nests against intruders.  Their usual population density is 1-6 chipmunks per hectare (Kurta 1995).

Tamias minimus hibernates when the weather is cold from October until April.  During that time, it frequently goes into torpor and lives off stored food in an underground burrow up to one meter below the surface (Kurta 1995).

The diet of T. minimus consists of seeds, nuts, fruits, berries (not the fleshy pulp but the seeds inside), grasses, green leaves, fungi, snails, insects, and small birds and mammals (Forbes 1966, Hamilton and Whitaker 1979).  It stores food in caches from midsummer into fall to be used when food is scarce.  Least chipmunks are able to remember when food patches are depleted of food and return first to those caches that are plentiful (Devenport et al. 1998).  They also mark depleted patches with urine to prevent wasting time harvesting depleted caches and thereby increasing foraging efficiency.  Least chipmunks are the only rodents to exhibit urine-marking behavior (Devenport et al. 1999).

Remarks:

Least chipmunks (Tamias minimus) used to have the scientific name of Eutamias minimus.  In 1977, Nadler at el. determined that Eutamias was not generically distinct from Tamias.  They recognized Tamias as consisting of the two subgenera, Eutamias and Neotamias, plus the subgenus Tamias.  Later in 1985, Levinson et al. also concluded that Tamias is the only genus of chipmunks and that there are two subgenera, Tamias, and Neotamias.  Today inclusion of Eutamias within Tamias, at least as a subgenus, has been generally accepted (Nowak 1997).

Literature Cited:

Devenport, L. D., J. A. Devenport and C. Kokesh. 1999.  Role of urine marking in the foraging behaviour of least chipmunks. Animal Behaviour. 57:557-563.

Devenport, L. D., J. A. Devenport and T. Humphries. 1998.  Future value and patch choice in least chipmunks. Animal Behaviour. 55:1571-1581.

Forbes, R. B. 1966. Studies of the biology of Minnesota chipmunks. American Midland Naturalist. 76:290-308.

Hamilton, W. J., Jr. and J. O. Whitaker. 1979. Mammals of Eastern United States. Comstock Publishing Associates, Ithaca and London.

Jackson, H. T. 1961. Mammals of Wisconsin. University Wisconsin Press, Madison, Wisconsin. xiii plus 504 p.

Kurta, A. 1995. Mammals of the Great Lakes Region. The University of Michigan Press, Ann Arbor, Michigan.

Long, C. A. 1970. Mammals of Central Wisconsin. Museum of Natural History Fauna and Floral Reports, University of Wisconsin-Stevens Point. No. 3. 59 p.

_____. 1976. The status of the least chipmunk (Eutamias minimus jacksoni) in Central Wisconsin. Reports on Mammals. Stevens Point, Wisconsin: Museum of Natural History, University of Wisconsin.

Nowak, R. M. 1997. “Walker’s mammals of the world online, Siberian and Western American chipmunks” (On-line), Available http://www.press.jhu.edu/books/walkers_mammals_of_the_world/rodentia/rodentia.sciuridae.eutamias.html . (December 4, 2003)

Schlimme, K. 1999. “Tamias minimus.”  <http://animaldiversity.ummz.umich.edu/accounts/tamias/t._minimus$narrative.html>.  Accessed December 4, 2003.

 
Reference written by Danielle Nelson, Biol 378: Edited by Chris Yahnke.
Page last updated 4-29-04.