How Do Squirrels Hibernate in The Winter?

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North American animal lovers are united in many varied ways, but the question of whether squirrels hibernate is one that tends to separate them.

Some individuals believe that squirrels hibernate and get up at different times while other individuals say that the animals are too small and their body cannot be able to store enough fat to keep them warm enough during hibernation.

The science world is also unsettled on the matter, and scientists, as well as animal experts, have researched on the same topic for decades.

During their research period, scientists have come up with several discoveries that might be useful to people soon. Therefore, let us look at some of the information about squirrels that science have discovered.

Squirrels Location


Squirrels are geographically found all over the continent except in Australia. Their size varies from large such as the Indian squirrels to very small such as Pygmy Squirrels found in Africa.

The squirrels in question here are North American ones, and they include the ground squirrel and the gray squirrel.

These two types of squirrels feed on grains, caterpillar, insects, fruits, roots, berries, seeds, or nuts. In some cases, they steal and eat eggs from nests although they are not their staple food.

What do the scientists and experts say on the ground and gray squirrel? Do squirrels hibernate or not?

Lincoln Park Zoo Website


Lincoln Park Zoo hosts many eastern gray squirrels within their habitation. These squirrels are not restricted in an enclosure but roam around the park freely.

The zoos experts say that this type of squirrels are homeotherms and therefore they do not hibernate. Homeotherms have the ability to regulate their temperature and maintain it all year-round.

Another website which is not authoritative as Lincoln Park also says the eastern gray squirrels do not hibernate during winter.

How do squirrels hibernate?

squirrels hibernation

Unlike the sea animals which hibernates for an entire winter season, ground animals among them squirrels partially hibernates and come out of hibernation to look for food.

Squirrels have a strong sense of smell, and therefore they often come out of hibernation once they sense a delicacy that is ready for them to eat. During the winter season, animal lovers feed their birds, rabbits, cats, and dogs outside the house.

Squirrels in their hiding place can tell the location of the feeding place and thus rush out to go and feed.

If the squirrels come out in large numbers, the people around them might assume that all the squirrels are active the entire day.

In reality, just a fraction of their population is outside their den with the rest of the population peacefully hibernating in hidden places waiting for their turn.

Some of the squirrels that might be running around the whole day may include gray squirrels.

Other Homes to squirrels

Two Squirrels

Some individuals say that college campuses and learning institutions are home to eastern gray squirrels. It is much easier for squirrels to find food to eat in campuses during winter than any other place.

Also, learning institutions have fewer predators such as cats and dogs. Nonetheless, individuals or experts who said squirrels hibernate clarified their point by stating that they were not talking about gray squirrels.

Brian Barnes Expertise

tree squirrel

Brian Barnes is a director at the Institute of Arctic Biology a subsection of the University of Alaska in Fairbanks.

In his article published by the National Wildlife Federation’s, he explains that hibernation is a reflex action of animals when they anticipate a famine to occur.

Famines are not always as a result of extremely dry conditions. Famines occur when animals lack food for a lengthy period due to changes in the environment.

During winter, plants that can provide food to the animals do not grow. Therefore, since food does not grow properly in cold conditions, winter can be considered as a famine by animals.

Barnes is a professional in hibernation, and he has studied and practised the discipline for over 40 years.

He discovered that animals that hibernate regulate the activity of their body cells so that the requirement for energy and oxygen is greatly reduced.

This mechanism helps the animals to survive longer because they experience less stress as compared to other animals within the same environment.

This mechanism scientifically known as homeotherm is one that scientists and researchers in the field of medicine and science, in general, are interested in learning.

After studying hibernation of animals, Barnes concluded that ground squirrels such as the eastern gray squirrel are the best hibernating animals.

His conclusion was based on the fact that ground squirrels have the capability to hibernate for longer periods as compared to other hibernating animals.

This mechanism helps the ground squirrels to live longer or survive extreme weather conditions for a long period. He also pointed out that squirrels have to wake up to urinate unlike bears since they are rodents.

Bears can shut down the activity of their kidney completely, and therefore they don’t experience the problem of waking up to urinate and then resuming hibernation.

Unlike many hibernating animals that lose their muscles or bones, squirrels and bears don’t have that problem.

This mechanism has elicited the interest of researchers to closely study the two animals with hopes of getting a cure or a remedy for patients suffering from broken bones or osteoporosis.

Another important aspect he is studying is how the slowed animals blood doesn’t clot. The discoveries from this question could be a solution to many patients suffering from heart diseases.

Squirrels Temperature during hibernation

Squirrel Eating

Zoologer website contains a lot of information about squirrel’s hibernation from Brian Barnes.

About two decades ago, Barnes conducted research on ground squirrels to study the change in squirrel’s body temperature during hibernation.

He captured some squirrels and implanted a radio device that would transmit information to him into them and then released the squirrels. He realized that the body temperature drops drastically.

In his further studies, he discovered that squirrels clean their blood regularly of any impurities in the blood that would cause their blood to crystalize to ice. Impurities act as agents of ice crystallization.

This mechanism prevents the squirrels from freezing. Unlike the fish which have anti-freezing hormone, squirrels use this mechanism to survive winter months.

Melanie Richter Expertise

do squirrels hibernate

Melanie Richter is an associate to Barnes. She also conducted her experiment on squirrel’s hibernations and investigate how low the squirrels’ temperature would fall.

She discovered that at temperatures of -26° C the squirrel started shivering. At this point, the body is triggered to produce heat, and that is when the squirrel came out of hibernation to find some source of energy which is food.

Another researcher by the name Eric T Pengelley conducted similar research on golden-mantled ground squirrel’s hibernation and posted a video of the squirrel’s behaviour online.

Eric T Pengelley is a professor at the University of California. From the video, we learn that an animal in hibernation has difficulties waking up.

This is because hibernation is a process that slows down life. Immediately an animal comes out of hibernation, the body’s activities start to increase slowly and gradually.

The environment of the enclosure must also be manipulated to make the air temperature warmer, and lighting must be increased to make the enclosure brighter.

The squirrel takes some time before it realizes that the environment has changed.

In the second video, the animal is still inactive, and the thermometer inside the animal reads at 4° C. The heartbeat of the animal also reads as four beats per minute as recorded by the EKG machine.

This, therefore, means that the animal is not sleeping but rather in a state of hibernation. The normal body temperature for ground squirrels are as high as 37° C and a heartbeat of around 400 beats/minute

Sleep does not change the physiological process of an animal to that degree even the deepest Sleep. Hibernation is the only explanation for such a state.

Sleep does not also hinder an animal from responding to the outside stimuli. Hibernation results to slow of body processes and an animal can take several hours to recover.

An animal from hibernation has difficulties eating, walking or even defending itself. Animals that wake up from sleep, stretch their muscles, roll around a bit and finally open their eyes.

A hibernating animal wakes up by first taking deep breaths at a slower rate than normal. As a result, the heartbeat increases gradually, and the temperature slowly increases.

Sleeping animals do not undergo all these processes, but rather they rapidly wake up and perform their normal activities. A hibernating animal will have to go through these processes.

Hibernating animals have a normal sleep only during warmer months during the mid of the day or at night. This also occurs in many non-hibernating animals.

Difference between hibernating and non-hibernating squirrels

Red Squirrels in the Snow

The difference between these two squirrels is well explained in the National Geographic Society website. The page says that some species live in tunnels or burrows and some others hibernate during winter.

In simple words, some squirrels do hibernate while other do not.

Scientists in the field of medicine are very curious on studying while the squirrels under hibernation don’t suffer from muscle atrophy.

They are also curious to study what mechanism the animals use to slow down the heart rate to search a low pace. Answers to these questions will provide a solution to several medical ailments.

Animal muscles function become fully active after the animals come out of hibernation. People who suffer from an induced or accidental coma, have difficulties with their muscles functioning after their recovery.

Soon, the answers to these questions will help thousands of patients waking up from a coma and live a normal life than years before.

How do squirrels hibernate in your area?

Grey Squirrel

As we have discovered above, only ground squirrels hibernate. The gray squirrels are exceptional and are only active during the morning and evening hours and sleep in between the day.

Their sleep cannot be compared to the hibernation of ground squirrels. Gray and ground squirrels go looking for food at different intervals, but ground squirrels return to hibernation state after feeding just like the bears do.

If your area has gray squirrels, observe them at morning and evening hours. During the day, they are sleeping. If your area has ground squirrels, you will have to wait for winter to fade for you to see them again.

It might seem like a stupid or a silly question, but it is very important. Researchers and scientists have spent their resources studying the hibernation of squirrels with the hope of getting answers that will help many people across the world.

Answers to this research question will improve the lives of people suffering from the diseases mentioned above.

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