How Do Chipmunk and Black Bear Hibernation Differ?

Eastern chipmunks (Tamias striatus) store food in a burrow system.

Black bears (Ursus americanus) store body fat.

Temperatures remain mostly above freezing because burrow entrances are plugged and the burrow system extends below frost line.

Temperatures usually approximate outside (often sub-zero) temperatures because den entrances usually are open and dens are shallow.

Body temperature drops to within a few degrees of the burrow temperature and is often around 40 F. Every few days, chipmunks elevate body temperature to over 94 F.

Body temperature drops from 100 F to between 88 and 97 F. Bears more efficiently maintain high body temperatures because of their lower surface to mass ratio, thicker insulation, and lower metabolic rate.

During periods when body temperature is over 94 F, chipmunks eat stored food, urinate, and defecate. Then they drop back into hibernation and repeat the cycle every few days.

Black bears have periods of sleep and wakefulness but can go all winter without eating, drinking, urinating, or defecating. Mothers wake up to give birth and take excellent care of the cubs in the den, licking them clean and responding to every cry for warmth and milk. Wild mothers ingest their cubs’ urine and feces. They also lick up drops of meltwater, eat snow and icicles, urinate, and defecate.

During the deep hibernation phase, chipmunks are slow to elevate body temperatures to responsive levels.

If handled during sleep, bears arouse more quickly than chipmunks do. However, see the exhibits on regional differences in black bear hibernation, fat versus skinny black bears, responses to warm weather, and mothers with newborn cubs.