You might think every squirrel hibernates, but nope, that’s not the case. Ground squirrels are the only ones that truly hibernate. Tree squirrels? They stay awake, using nests and food stashes to get through the cold months. Let’s dig into which squirrels really sleep the winter away and which just slow down a bit—so next time you spot a fluffy tail in the snow, you’ll know what’s up.
Ground squirrels drop their body temperature and heart rate for months at a time. Tree squirrels, though, depend on their food stashes, thicker coats, and short naps instead of hibernating.
It’s actually pretty fascinating to see what hibernation really means out in the wild.
Which Squirrels Hibernate
Most ground squirrels sleep through winter, while tree squirrels stay somewhat active. Tree squirrels use short torpor periods and rely on stored food or nests.
You’ll see which types actually hibernate, how their bodies change, and which species act most dramatically during winter.
Differences Between Tree Squirrels and Ground Squirrels
Tree squirrels, like gray and fox squirrels, don’t hibernate. They reduce how much they move around, use dreys or tree holes, and dig up hidden nuts on milder days.
Flying squirrels skip hibernation too. They usually huddle up in tree cavities to stay warm together.
Ground squirrels, on the other hand, live in burrows and actually hibernate. In cold climates or open grasslands, you’ll notice these squirrels disappear for months.
Chipmunks and many ground squirrels gather food and then stay in their burrows for ages. That means you might spot tree squirrels on a warm winter day, but ground squirrels? They’re gone until spring.
Species That Hibernate: Ground Squirrels Explained
Species like the California ground squirrel and a bunch of other ground-dwelling types hibernate. These little guys head underground in late fall and stay there for months.
They don’t eat during hibernation—they just live off the fat they built up during summer and fall.
Up north or in high places, you’re way more likely to run into true hibernators. Some time their hibernation with the length of the day or how cold the soil gets.
Ground squirrels often seal up their burrow entrances and barely move to save energy. Once the ground warms up and food returns, you’ll see them pop back out.
Physiological Changes During Hibernation
When ground squirrels hibernate, their body temperature drops a lot. Their heart and breathing slow way down, and their metabolism nearly stops.
This lets them survive for months without food.
Torpor is a lighter, shorter sleep. Tree squirrels use torpor for a few hours or maybe a day when it gets really cold.
Unlike deep hibernators, squirrels in torpor can wake up quickly to grab a snack. The Arctic ground squirrel drops its temperature the most—sometimes almost freezing—while others, like the California ground squirrel, don’t go quite as low.
Notable Examples: Arctic Ground Squirrel and Thirteen-Lined Ground Squirrel
The Arctic ground squirrel takes hibernation to the extreme. It can chill its body down to about 32°F and stay that way for months.
You won’t see one above ground in the Arctic until spring rolls around.
The Thirteen-lined Ground Squirrel (Ictidomys tridecemlineatus) hibernates for long stretches in prairies and grasslands. It fattens up in late summer, heads underground, and cycles through deep sleep and brief wake-ups.
These squirrels really show what true hibernation looks like—way more intense than the light torpor tree and flying squirrels use.
How Squirrels Survive Winter Without Hibernating
Squirrels that don’t hibernate make it through winter by using food they’ve hidden, putting on extra fat, and building warm nests.
You’ll sometimes catch them digging up their stashes, curling up in tree holes or dreys, and keeping their babies safe from the cold.
Food Storage and Fat Reserves
Squirrels hide food in lots of little spots, called scatter hoards. If you watch a gray squirrel, you’ll probably see it burying acorns, walnuts, or sunflower seeds around the yard.
They use memory, scent, and even landmarks to find some of these hiding places later. They don’t always remember every spot, but honestly, who would?
Before winter, squirrels eat more to bulk up. That extra fat helps them on freezing days when food is tough to find.
Mother squirrels especially need more calories—they have to nurse and keep their babies warm.
Tree squirrels mostly count on their food caches. Some squirrels also store bigger piles of food in safer places.
You might notice them running back and forth, hiding food in dozens of spots all over your yard.
Winter Nests: Dreys and Burrows
Dreys are those messy-looking nests made of twigs, leaves, and moss, usually wedged in the forks of tree branches or tucked into dense evergreens.
If you look up, you might spot a drey as a round bundle high in the trees. Dreys block wind and help keep the squirrel warm.
Tree squirrels also use tree cavities and old woodpecker holes. Cavities are better for babies, especially during storms or when raising a litter in late winter.
Ground squirrels and some others use burrows—underground tunnels that stay warmer than the surface.
Squirrels line their nests with grass, shredded bark, or even fur. In rough weather, they might share nests—flying squirrels, for example, often snuggle together for warmth.
If you see small entry holes, droppings, or chewed bark, there’s a good chance a drey or cavity has a squirrel inside.
Adaptations in Tree Squirrels and Flying Squirrels
Tree squirrels stay active and alert, even when it’s cold out. On the chilliest days, they cut back on activity but still head out to forage.
Their thick winter fur keeps them warm, and they’ll use their tails like blankets when they curl up. Sometimes, you might spot a squirrel wrapping its tail around itself while it rests on a branch.
Flying squirrels do things a bit differently. They drop their body temperature a little and roost inside tree cavities or squeeze into communal nests.
They use soft chit-chat calls to locate their group, then huddle together at night. This cozy social nesting really helps them—and their babies—get through those long, cold spells.
Both kinds of squirrels plan reproduction so the babies arrive when food’s back. If you stumble across a quiet nest with soft material in spring, there’s a good chance it’s sheltering baby squirrels born after winter.
