A Chipmunk’s Winter Sleep (Torpor and Hibernation)


A chipmunk among leaves. Photo by Donna L. Long.
A chipmunk among leaves. Photo by Donna L. Long.

When the weather grows chilly, I imagine chipmunks snug in their burrows, peacefully sleeping away the cold winter months. During autumn they spend their time gathering food to last the long, cold winter. I like chipmunks. I like their small size. I like their soft earthy colors. I like their spunk and energy. 

In North America, there are 25 species of chipmunks. Here in the eastern United States, the Eastern Chipmunk is the most common and widespread species. The Eastern Chipmunk ranges from Quebec west to Manitoba south to Georgia. The Eastern species lives throughout Pennsylvania and Philadelphia.

The English word “chipmunk” is a corruption of the name for the animal in Ojibwa, adjidaumo (the “o” at the end has a nasal pronunciation). The name, adjidaumo, means “head first”, the way in which chipmunks climb down a tree.

A close-up of a chipmunk's fur and markings. Photo by Donna L. Long.
A close-up of a chipmunk’s fur and markings. Photo by Donna L. Long.

Both males and females have the same coloring of reddish brown fur with one thin black stripe running down their spine. Two black stripes are on each side of their bodies with a white stripe in-between. Two white stripes swipe across their cheeks with a black stripe between them. And another black stripe runs their the eye with two white stripes on either side. 

The Eastern Chipmunk in the photos was scurrying around at Fort Washington State Park during autumn. I was on the hawk watching platform watching hawks and other raptors flying high above during the fall migration. 

I often look for chipmunks. The many stone walls in the Philadelphia area are good places to observe chipmunks. Apparently, they like having entrances among the stones leading to their underground burrows.

A chipmunk digging in the soil. Photo by Donna L. Long.
A chipmunk digging in the soil. Photo by Donna L. Long.

Eastern Chipmunks are semi-fossorial (underground dwelling) and strictly diurnal (active during daylight) . They are most active around noontime. Chipmunks spend most of their time underground, except for when they forage for food above ground. They are most active on bright, warm, windless days. When not active above ground, chipmunks retire to underground burrows. On hot days they will seek the coolness below the ground’s surface.

Their burrows are about two feet below ground.The one chamber serves as bedroom and food store. A back tunnel and entrance is plugged to prevent other animals from entering.

A chipmunk chewing something. Photo by Donna L. Long.
A chipmunk chewing something. Photo by Donna L. Long.

Chipmunks can feed up in trees, 65 feet above the ground. They are mostly vegetarian but they do eat animal matter such as earthworms, June bugs, worms, grasshoppers, frogs, reptiles, bird eggs, and even small animals when they can catch them.
Autumn is harvest time for chipmunks. Chipmunks store nuts and seeds in their burrows to eat all winter long and into the often food scarce spring. Chipmunks gather beech nuts, hazelnuts, hickory nuts, acorns, and fungi. 

Chipmunks have incredibly large, stretchy cheek pouches each of which is the size of its skull. They use their pouches to transport food and soil removed from digging out their burrows.

Many of us were taught in school that chipmunks were true hibernators Chipmunks don’t hibernate. Chipmunks and bears have something in common, they both experience torpor, not hibernation. Eastern Chipmunks enter their burrows for winter sleeps in late October or early November. They close up their burrows entrances with soil and vegetation. The is just one chamber in their burrows which services as both bedchamber and food pantry.(link to bears and hibernation post)

Eastern Chipmunks enter periods of deep sleep, called torpor. During the winter in their burrows, they wake and go back to sleep, repeatedly. A slumbering chipmunk sleeps curled up into a ball, with its’ fur fluffed up for insulation.


A chipmunk among leaves. Photo by Donna L. Long.
A chipmunk among leaves. Photo by Donna L. Long.

When it enters torpor, it’s heart rate drops from 350 beats per minute to 4 beats per minute. Its body temperature drops from 98.6 degrees Fahrenheit (37 degree Celsius) to only 1 or 2 degrees above the air temperature in the burrow. Temperatures below ground generally stay just above freezing. In the cold but not freezing burrow, chipmunks are protected from the dangers of freezing to death. 

A close up of a chipmunk's face. Photo by Donna L. Long
A close up of a chipmunk’s face. Photo by Donna L. Long

Chipmunks don’t develop a thick layer of body fat to last the winter. They must wake up periodically to eat and keep their bodies functioning. Each period of wakefulness can last several days. When they wake up, chipmunks urinate and eat some of their stored food.
The last few days here in Philadelphia have been far colder than we are used to at this time of year. Last week’s Nor’easter that brought snow and frigid below zero temperatures. In three days the temperature high is expected to climb to 60 degrees Fahrenheit. I wouldn’t be surprised if a few chipmunks are seen running around stretching their legs. 

Identify other mammals in my Mammal Photo Gallery

Read more about Chipmunk on Wikipedia

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