Young of chipmunks vary in number from four to six. Nests are constructed of dry grass and are placed under rocks, logs, and in burrows in the ground. There are four pairs of mammae, one pectoral, two abdominal, and one inguinal.
Tamias minimus Bachman
Least chipmunk
Description.—The least chipmunk is the smallest chipmunk found in Washington. The head and body of adults measure about 3-1/2 inches; the tail about 3-1/2 inches. Its fur is short and sleek. The dorsal stripe is black; the upper pale stripe is buffy gray; the lower dark stripe is rich brown; the lower stripe is white. The sides are pale buff and the head, rump and thighs are buffy gray. The tail is brownish above, yellowish beneath.
Tamias minimus has a wide range, being found from the Cascade-Sierra Nevada Chain to the Great Lakes and from northern Canada to central Arizona and New Mexico. Two races occur in Washington, both in the sagebrush desert area.
Least chipmunks are only locally common in Washington. I have found them in areas where the soil was firmly packed and sagebrush the dominant vegetation. All were far from water. Two miles west of Vantage, Kittitas County, several were found near an old sheep corral, where one took shelter in a pile of boards. In my experience, least chipmunks are wary and difficult to collect. Many times as I crept silently through the sagebrush chipmunk after chipmunk scampered with tail aloft into a hole at the base of same sage bush, each far out of gunshot, voicing alarmed chirps. The extreme caution of least chipmunks, as compared with other species, is doubtless a necessary adaptation to living in an exposed situation. The open sagebrush desert is a favored hunting place of hawks and eagles; also coyotes, wildcats, and badgers sometimes abound there. All these probably find the least chipmunk a suitable food item and only the most cautious chipmunk survives to reproduce. The least chipmunk has been timed at a speed of 10 miles per hour ([Cottam] and Williams, 1943: 262).
The food of the least chipmunk in eastern Washington is almost entirely seeds of the annuals that flourish briefly in the spring. Insects probably are eaten and one specimen had the remains of two scorpions in its stomach.
Tamias minimus scrutator ([Hall] and Hatfield)
Eutamias minimus pictus [Howell], N. Amer. Fauna, 52:39, November 30, 1929.
Eutamias minimus scrutator [Hall] and Hatfield, Univ. California Publ. Zoöl., 40:321, February 12, 1934.