The answer to the question, “Do squirrels hibernate?” is… it depends on the species of squirrel.
Arboreal squirrels, like grey and red squirrels, do not hibernate. Instead, they collect enough food to last them through the winter. They stash this food underground, where they can access it later when food is scarce. This ensures they have a constant supply of food all year round, even during the harsh winter months. They keep warm throughout the winter in nests. During the summer it is common to see squirrel dreys in the trees. In the winter, they often find cosier places to nest, like holes inside tree trunks. They pad their nests out with leaves and moss to keep them warm. In the winter, these tree squirrels sleep a lot more to conserve energy. But they don’t hibernate.
Some ground squirrels, however, do hibernate.
What is hibernation?
Hibernation is a behavior some warm-blooded animals use to survive the winter. It is sometimes described as a deep sleep, but hibernation is more than that. The body almost completely shuts down. In fact, normal body metabolism is reduced to just 5% to conserve energy. It keeps going just enough to keep the animal breathing, its heart pumping, and its body warm enough to survive. Very little energy is used during hibernation so the animal doesn’t have to find food or water to survive. It is an ideal survival strategy if there isn’t much food around during cold winters.
Which ground squirrels hibernate?
The 13-lined ground squirrel, or striped gopher, is native to North America and hibernates for up to 6 months each year. This is also true of marmots, which are larger, stockier ground squirrels also found in North America as well as Canada.
Throughout the summer, the ground squirrels build up a heavy layer of fat. They live in burrows underground, usually a couple of feet below the surface with a deeper hibernation chamber. Marmots can have burrows over 20 feet deep!
Ground squirrels typically settle down to hibernate in September or October and don’t emerge until March, April, or even May.
Like all hibernating mammals, ground squirrels survive months without food and water by greatly slowing down their metabolism. Their breathing rate is usually between 100 and 200 breaths per minute. During hibernation, this can reduce to just one breath every five minutes! Their body temperature drops, so they don’t expend energy keeping warm. Their heart rates reduce, from about 100 beats per minute (at rest) to 400 (when running) during the summer, to as low as 3 beats per minute during hibernation.
They can suppress their thirst, protect their muscle cells from inactivity, and use stored fat for energy.
Hibernation is a clever survival strategy, but animals can die if they fail to wake up or don’t store enough fat beforehand.
Scientists now believe our ancestors could go into some kind of hibernation when food resources were scarce. They are now considering whether hibernation in humans could be beneficial to our health and could help combat diseases. It’s an interesting thought.
Watch this Arctic squirrel hibernating
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Glossary
Arboreal: living in trees
Drey: a squirrel nest, usually made from twigs in a tree
Metabolism: chemical reactions inside our bodies which keep us alive, including the breakdown of food and water to be used by the body
References
Wikipedia (2023) Thirteen lined ground squirrel. https://en.m.wikipedia.org/wiki/Thirteen-lined_ground_squirrel Accessed on February 13th, 2023.
Frederick, E. (2019) Here’s how hibernating squirrels live for months without water. https://www.science.org/content/article/here-s-how-hibernating-squirrels-live-months-without-water Accessed on February 13th 2023
Integrum Services (2023) https://integrumservices.co.uk/pest-control-blog/do-squirrels-hibernate/ Accessed on February 13th 2023
Wilkins, A. (2022) Human hibernation is a real possibility – this is how it might work. https://www.newscientist.com/article/mg25634080-400-human-hibernation-is-a-real-possibility-this-is-how-it-might-work/ Accessed on February 13th, 2023
Ignat’ev, D.A. (2001) Analysis of changes in heart rate and temperature of the ground squirrel https://pubmed.ncbi.nlm.nih.gov/11236592/ Accessed on February 13th 2023
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