Naturalists, as well as many ordinary observers, it is said, recognize numerous varieties among the chipmunks of the United States, founded principally on the markings of the fur; for in their habits they are all very similar. Elliott Coues describes four varieties found in this country.
The American chipmunk, hackee, or chipping squirrel (_Tamias lysteri_) is distributed all over the United States. The face is of a reddish brown tint, with darker spots on the forehead and cheeks; the nape of the neck is ashen gray, the hind-quarters reddish brown, the under surface whitish; there is a dark-brown stripe on the back, a black stripe over the eye, with white above and below it, and there is a wide white side-streak edged with blackish brown; the upper surface of the tail is dark-brown, the base being grayish yellow, the tip whitish and the lower surface a ruddy hue.
This description may seem superfluous, in view of our picture of the lively little animal; we think, however, it may induce closer observation of the markings of its fur.
The chipmunk is visible at all seasons of the year, but late in summer it may be seen running about, "its cheek pouches filled and its eyes beaming with the satisfaction which its riches afford it." According to the different months in which they mature, it gathers its varied stores, for the most part consisting of buckwheat, hazelnuts, maple seeds, and corn. During the winter it hibernates to some extent, but it seems to stand in need of food during the whole winter. Audubon dug up a burrow in January, and at the depth of about four feet he found a large nest of leaves and grass in which were three chipmunks; others seemed to have disappeared in the lateral passages at the approach of the diggers. The animals were overcome with sleep and not very active, but they were not as torpid as true hibernating animals are, and they snapped viciously at the naturalist, who tried to handle them. The animal does not become torpid before November. It does not leave its subterranean home during the winter, but keeps a passage open. When the snow melts it begins its activity above ground.
The young are born in May, and a second litter usually in August. It is said the males engage in fierce combats during the breeding-season.