Chipmunks are among many animal species that hibernate during the winter months. But, unlike true hibernators such as woodchucks, chipmunks wake periodically and return to their hibernation. Not all chipmunks overwinter in sleep; those who do have varying hibernation schedules, even within a single habitat. When they hibernate, their body processes slow and they sleep for days or weeks.
Heartbeat and Breathing
Essential to hibernating is the chipmunk's ability to slow his heart rate so his body isn't using much energy. Normally pumping at around 350 beats per minute, his heart pumps only about 15 times per minute while hibernating. His respiration rates also slow. An active chipmunk might breathe 60 times per minute; during hibernation, he takes about 20 breaths per minute.
The warm-blooded chipmunk adapts colder body temperatures when hibernating. This allows him to sleep longer by reducing the amount of heat his body must produce. Awake and active, a chipmunk might have a body temperature of between 96 and 106 degrees Fahrenheit, but it can drop to as low as 42 degrees when the animal hibernates.
Unlike true hibernators, chipmunks don't sleep all winter. Their state is more of a dormancy, rather than true hibernation, because they wake often. True hibernators store layers of fat before winter sets in, and their bodies use the fat for sustenance the creatures sleep. A chipmunk's body might use some fat while sleeping, but the creature wakes periodically to eat seeds and nuts and to take care of his potty business. He then drifts back off to sleep for another few days or weeks until his hunger awakens him again.
When Not Hibernating
During the warmer months, chipmunks spend the time immediately after waking eating and rebuilding fat lost during hibernation. They enjoy plentiful eating during the summer; when fall rolls around, they find a nice place to nest for the winter, usually in an underground burrow. They start storing food in the burrow to munch on during hibernation so they won't have to leave the nest until warm weather arrives. True hibernators prepare for months so their bodies have enough fat, but chipmunks make sure to store enough seeds and nuts instead.