Although it sometimes climbs trees and shrubs to find food, the eastern chipmunk spends most of its time on the ground, where it excavates fairly extensive burrow systems (1) (2) (3) (4) (5). The burrow is usually built beneath a log or rock, at the base of a tree or under the edge of a building (1) (3), and generally consists of a series of interconnected tunnels with multiple entrances (2) (4). A nest of crushed or chewed leaves is built in an enlarged chamber, while other chambers are used to store food (4) (5) (6). On rare occasions, the eastern chipmunk has also been known to rear its young in a nest in a hollow tree (5) (6).
The eastern chipmunk is generally solitary and territorial, vigorously defending the area around its burrow against intruders (1) (3) (4) (5) (7). Active during the day, this small mammal feeds on a variety of seeds, fruits and nuts, as well as mushrooms, insects, earthworms, slugs, snails and birds’ eggs. It even sometimes takes small snakes, frogs, mammals and birds (2) (3) (4) (5) (6) (7).
Like other chipmunks, the eastern chipmunk has large internal cheek pouches which are used to carry food (3) (5) (6). Dry foods such as nuts and seeds are gathered in large quantities in late summer and autumn and transported back to the burrow to be stored for the winter (2) (4) (5) (7). This behaviour is aptly described by the eastern chipmunk’s scientific name, Tamias, which means ‘storer’ (5).
The eastern chipmunk hibernates in its underground burrow from around October to February or March, depending on the location (2) (3) (5) (7). Unlike many other hibernating mammals, the eastern chipmunk does not accumulate significant stores of body fat before winter, instead living off the food it has stored in its burrow. This means the chipmunk must wake frequently to feed, and it may even leave the burrow on warm days (2) (3) (4) (6) (7). The degree of torpor varies between individuals and between populations, with some remaining dormant throughout the winter, while others are more active (3) (5) (6).
Male eastern chipmunks typically emerge from hibernation earlier than females (5) (7), although severe weather may cause both to return to their burrows (3) (5). Uniquely among hibernating Sciuridae species, the eastern chipmunk can have two breeding periods a year (3) (5) (7), the first between February and April and the second between about June and August (1) (3) (6).
The female eastern chipmunk usually gives birth to a litter of around 3 to 5 young in an underground nest, after a gestation period of 31 days (1) (2) (4) (6). The young are born blind and hairless, weighing about three grams (3) (4), and emerge from the burrow five to six weeks later (3) (5). Some female eastern chipmunks may go on to have second litter later in the summer (2) (3) (5) (7).
Young eastern chipmunks reach adult size by about three months old (3) (6). A few females born in the spring may mate in the summer breeding season, but most individuals do not breed for the first time until the following year (3) (4) (5) (6). The eastern chipmunk usually lives for two to three years in the wild (1) (2) (3), although some have reached up to eight years in captivity (3) (5). This species is vulnerable to a range of predators, including snakes, weasels, foxes, bobcats, domestic cats and dogs, coyotes, hawks and owls (4) (5) (6).