As autumn leaves paint the landscape and a chill enters the air, a familiar question arises for many homeowners and nature lovers: Where did all the squirrels go? The frantic scampering and acorn-burying frenzies seem to cease overnight, leading many to wonder, “Do squirrels hibernate?”
The answer isn’t a simple yes or no, and it reveals a fascinating world of animal adaptation. While some types of squirrels are true hibernators, the common tree squirrels you see in your backyard have a completely different and equally clever strategy for surviving the winter.
This guide will unravel the surprising truth. We’ll explore which squirrels enter a deep winter sleep, what the others do instead, and answer all your questions about their cold-weather habits.
The Short Answer: Not All Squirrels Truly Hibernate
To be clear: Most squirrels you see every day, like the common Eastern Gray Squirrel, do not hibernate.
Instead of entering a months-long deep sleep, these squirrels have adapted to simply endure the winter. They reduce their activity and rely on a different, less extreme survival state called torpor.
- True Hibernation: A long-term state of inactivity where an animal’s body temperature, heart rate, and metabolism drop dramatically. An animal in true hibernation is nearly impossible to wake.
- Torpor: A short-term, involuntary state of reduced activity and metabolism. It can last for a few hours or a few days. Squirrels in torpor can wake up relatively quickly to eat or if threatened.
So, when you don’t see your backyard squirrels for a couple of days during a snowstorm, they aren’t hibernating. They’re likely curled up in their nests in a state of torpor, conserving energy until the weather improves.
True Hibernators: The Ground Squirrel Exception
While tree squirrels are active intermittently throughout the winter, some of their cousins are champions of deep sleep. Ground squirrels are true hibernators.
Species like the California Ground Squirrel, Richardson’s Ground Squirrel, and the incredible Arctic Ground Squirrel undergo one of the most extreme physical transformations in the animal kingdom.
During hibernation:
- Their body temperature can plummet from around 99°F (37°C) to just above freezing. The Arctic Ground Squirrel has been recorded with body temperatures just below 32°F (0°C).
- Their heart rate slows dramatically, dropping from over 300 beats per minute to as few as 5.
- Their metabolism slows to a crawl, allowing them to survive for months on their stored body fat alone.
These ground-dwelling rodents retreat to their underground burrows in the fall and don’t emerge until the warmth of spring arrives.
Common Tree Squirrels: A Strategy of Torpor and Caching
So, if they aren’t truly hibernating, what are the common tree squirrels doing to survive? Their strategy is a two-part system: preparing in the fall and conserving energy in the winter.
Eastern Gray and Fox Squirrels
These are the most common squirrels in the United States. In the fall, they enter a manic period of food gathering called “scatter-hoarding.” They bury thousands of nuts and acorns in individual locations across their territory. Their impressive spatial memory allows them to retrieve these caches throughout the winter.
During the coldest spells, they stay in their nests, called dreys (messy-looking balls of leaves and twigs high in trees), entering a state of torpor to save energy. On milder, sunny winter days, you’ll see them out and about, digging up their buried treasures.
American Red Squirrels
Red squirrels practice a different food-hoarding strategy. Instead of scattering their food, they create one large cache, called a midden. This huge pile of cones, nuts, and other food is often located in a cool, damp place, like a hollow log, which helps preserve the food. They fiercely defend this single, vital food source all winter.
Flying Squirrels
These nocturnal squirrels also do not hibernate. To combat the cold, they employ a social strategy. Up to 20 or more flying squirrels will huddle together in a single tree cavity or nest to share body heat, a behavior known as “communal nesting.”
The Hibernation Calendar: When, Where, and How Long?
For squirrels that do hibernate or enter torpor, timing is everything.
- When does it start? Ground squirrels typically enter their burrows for hibernation in late fall (October or November), depending on the climate. Tree squirrels will begin using torpor during the first deep freezes of winter.
- How long does it last? True hibernation for a ground squirrel can last from 3 to 7 months. Torpor for a tree squirrel is much shorter, lasting from a few hours to several days at a time.
- Where do they go?
- Tree Squirrels: They retreat to leaf nests (dreys) or more permanent dens in hollow trees (cavities).
- Ground Squirrels: They seal themselves inside extensive underground burrows.
- In Houses: Yes, squirrels will take advantage of warm, safe spaces like attics or walls to build their nests, especially during winter.
Hibernation by Location: From Florida to Michigan
A squirrel’s winter behavior is heavily influenced by its location.
- In Southern States (like Florida, Texas): Winters are mild. Squirrels here remain active year-round and have little to no need for hibernation or extended torpor. They may stay in their nests during a rare cold snap, but their behavior changes very little.
- In Northern States (like Michigan, Minnesota, New England): Winters are harsh and long. Here, tree squirrels will spend significant time in torpor, and ground squirrels will be in true hibernation for many months.
Squirrels vs. Chipmunks: A Tale of Two Rodents
People often group squirrels and chipmunks together, but their winter habits are quite different. Chipmunks are true hibernators.
Like ground squirrels, they retreat to burrows and enter a state of deep sleep. However, they don’t rely solely on body fat. They wake up every few days to eat from a food stash inside their burrow and to urinate, then go back to sleep.
Frequently Asked Questions (FAQ)
A: True hibernators like ground squirrels begin entering hibernation when soil temperatures drop and food becomes scarce, often in the 40-50°F (4-10°C) range. Tree squirrels enter torpor during periods of extreme cold, especially when it’s below freezing.
A: True hibernators do not eat or drink; they live off their fat reserves. Tree squirrels in torpor will wake up to eat from their food caches.
A: A pet squirrel living in a climate-controlled home with a steady food supply has no environmental reason to hibernate or enter torpor.
A: It depends on the type. Ground squirrels hibernate underground in burrows. Tree squirrels spend the winter in nests (dreys) or cavities high up in trees.
Conclusion: A Winter of Clever Survival
So, while most of the squirrels darting across our parks and yards don’t technically hibernate, their winter survival story is no less remarkable. Through a combination of meticulous food storing, energy-saving torpor, and cozy nests, tree squirrels have mastered the art of enduring the cold.
Meanwhile, their ground-dwelling cousins take a more extreme approach, shutting down their bodies for months in one of nature’s most incredible feats of survival. The next time you see a squirrel on a mild winter day, you’ll know it’s not a hibernator that woke up early—it’s a resourceful survivor making a well-timed trip to its pantry.
