Chipmunk, the name usually given to the ground squirrel (tamias, Illig). The ground squirrels have cheek pouches extending to the hind head and opening internally; the tail is shorter than the body, the feet large, with well developed claws for digging, and the anterior basal plate of the zygoma perforated by a nearly circular foramen; the permanent upper molars are four; the tail is not bushy, and there are three to five longitudinal stripes on the back. They burrow in the ground near the roots of trees, and their nest is well supplied with winter food. They form a connecting link between the squirrels proper and the spermophiles or prairie squirrels. The common American ground, striped, or cheeping squirrel, chipmunk, or hackee (T. striatus), has the body 5 to 6 in. long, and the tail about 4 1/2; on the back and sides arc five longitudinal black stripes, not extending over the rump, the outer two on each side separated only by a white line; rump pale chestnut, and the upper parts generally finely grizzled yellowish gray and brown; lids and under parts white, and a downy white spot behind the ears.
It varies but little, and is found from Canada and Lake Superior to Virginia and Missouri. It is lively, playful, and busy, and may be said to occupy among mammals the place of the wren among birds; it is very commonly seen running along the fences and walls in New England, cheeping like a young chicken, the cheek pouches distended with nuts or seeds, occasionally stopping and standing upright, watching against enemies, and disappearing in some hole at the least alarm. The young are born in May, four or five at a birth. They are scarcely injurious to the farmer, not disturbing the grain before it is ripe, and only gleaning after the harvest; they feed chiefly on nuts, wheat, buckwheat, Indian corn, cherry stones, and grass seeds, with which their winter burrows are plentifully supplied. They are easily captured in traps, but are not readily tamed, and are rarely seen in cages. Their worst enemy is the weasel, which pursues them into their burrows. The Missouri chipmunk (T. quadrivit-tatus) is smaller, with the intervals between the stripes all grayish white; beneath it is dirty grayish white, and the general color is more ferruginous; it most resembles the T. Pallasii of N. Asia and Siberia, and occurs about and west of the Rocky mountains.
Other species are found on the Pacific coast.