“Some rodents hibernate, including groundhogs, marmots, many ground squirrels, chipmunks, dormice, and some prairie dogs. Others, like tree squirrels, beavers, muskrats, rats, mice, and capybaras, stay active all winter. Pet rodents should never hibernate; a hamster that gets too cold can slip into a dangerous torpor that needs immediate warming.”
When winter arrives, rodents face a tough problem: food becomes scarce while staying warm takes more energy. Different species solve it in very different ways. Some shut down almost completely for months, some take short naps of reduced activity, and others simply stay busy with stored food and warm nests. Here’s how rodent hibernation works and which species use it.
Hibernation vs Torpor: What’s the Difference?
- Torpor is a short-term state of lowered body temperature, heart rate, and metabolism, lasting hours to a few days.
- Hibernation is a long series of deep torpor bouts that can last weeks or months, broken by brief periods of arousal.
Both save energy when food is scarce. True hibernators prepare months in advance by fattening up or storing food.
Rodents That Hibernate
| Rodent | Hibernation Style |
|---|---|
| Groundhogs and marmots | Deep hibernation for several months, living on body fat |
| Ground squirrels | Deep hibernation; Arctic ground squirrels can drop below freezing |
| Chipmunks | Torpor bouts, waking to eat from food stores |
| Dormice | Long hibernation, often six months or more |
| White-tailed, Gunnison’s, and Utah prairie dogs | Hibernate through winter |
| Jumping mice | Long hibernation in underground nests |
| European hamster | Hibernates, waking to eat stored food |
Groundhogs
Groundhogs are classic hibernators. Their body temperature falls from around 99°F to about 40°F, and their heart rate drops from roughly 80 beats per minute to a handful. See groundhog facts.
Arctic Ground Squirrels
These squirrels hold a record: their body temperature can drop slightly below the freezing point of water during hibernation, lower than any other known mammal, without their tissues freezing. They periodically rewarm, then cool again, throughout winter.
Chipmunks
Chipmunks store large caches of seeds and nuts in their burrows. Rather than relying on fat, they enter torpor for several days at a time and wake up to snack from their stores.
Dormice
Dormice are such dedicated sleepers that their name may come from a word meaning “to sleep.” The hazel dormouse can hibernate for around half the year. See dormouse facts.
Rodents That Stay Active All Winter
- Tree squirrels: gray, fox, and red squirrels rely on food caches and warm nests. See types of squirrels.
- Beavers: stay inside insulated lodges and swim under ice to underwater food caches. See beaver facts.
- Muskrats: stay active under ice, using lodges and push-ups. See muskrat facts.
- Voles and lemmings: live and even breed under the snow. See voles and lemmings.
- Porcupines: feed on tree bark all winter. See porcupine facts.
- Black-tailed prairie dogs: stay active on mild days and use short torpor in cold snaps.
- Rats and mice: stay active, often sheltering in buildings.
- Capybaras: tropical animals that never hibernate. See capybaras in winter.
How Hibernators Prepare
- Fattening up: many hibernators eat heavily in late summer and fall, sometimes nearly doubling their body fat.
- Food storing: others, like chipmunks and European hamsters, fill underground pantries.
- Building a hibernaculum: a protected nest chamber below the frost line or in a tree hollow.
- Timing: shortening days and falling temperatures trigger hormonal changes that prepare the body.
Why Do Hibernators Wake Up Periodically?
Most hibernating rodents rouse briefly every week or two, raising their body temperature to near normal before cooling again. These arousals use a lot of energy, so they must be important. Scientists think they may help with immune function, sleep, and clearing waste products, but the exact reasons are still being studied.
What About Pet Rodents?
Pet rodents shouldn’t hibernate. Even species with wild relatives that hibernate aren’t prepared for it in captivity; they lack the fat reserves, food stores, and gradual conditioning. The biggest risk is with pet hamsters:
- If the room drops below about the low 60s °F, a hamster may enter torpor.
- A torpid hamster is cold, limp, and breathing very slowly, and can be mistaken for dead.
- Warm it gradually in your hands or in a warm room, and contact a vet.
Keep pet rodents in a room around 65 to 75°F year-round. See winter care for pet rodents and hamster care.
Hibernation Research
Hibernating rodents fascinate scientists and doctors. Their ability to survive extreme cold, low oxygen, and months without eating, then recover without lasting damage, may offer clues for medicine, such as protecting organs during surgery or storing organs for transplant. Groundhogs and ground squirrels are among the most studied species.
Hibernation and Climate Change
Warmer winters and earlier springs are changing when some rodents enter and leave hibernation. Studies of yellow-bellied marmots in Colorado, for example, found that longer growing seasons allowed marmots to emerge earlier and grow larger. Such changes can have complex effects on survival and food availability. See rodents and climate change.
How Non-Hibernators Survive Winter
Rodents that stay active have their own clever strategies. Tree squirrels grow thicker winter coats, build insulated leaf nests or use tree cavities, and rely on thousands of buried nuts. Red squirrels store cones in large central piles called middens. Voles and lemmings live in the space between the ground and the snowpack, where temperatures stay near freezing even when the air above is far colder. Beavers and muskrats stay warm in lodges and feed from underwater caches. Mice often huddle together in nests to share warmth, and many move into buildings.
Some small rodents also use short bouts of torpor on especially cold nights, even if they don’t hibernate. This flexible approach lets them save energy only when conditions demand it.
Signs of Hibernation in the Wild
If you notice a groundhog or chipmunk disappearing from your yard in fall, it has likely settled into its burrow for the winter. Don’t disturb burrows during this time. Waking a hibernating animal forces it to burn precious fat reserves it needs to survive until spring.
Frequently Asked Questions
Do squirrels hibernate?
Tree squirrels don’t hibernate, but many ground squirrels do.
Do hamsters hibernate?
Some wild hamsters do, but pet hamsters shouldn’t. Cold can trigger a dangerous torpor.
Do mice hibernate?
House mice don’t. Some wild species, like jumping mice, do.
How long do groundhogs hibernate?
Usually about three to five months, depending on the climate.