Ever notice how you see way fewer squirrels in winter? Maybe you’ve wondered if they just sleep through the cold. Some squirrels really do hibernate, but most don’t—ground squirrels go into deep hibernation, while tree squirrels just slow down and stay cozy in their nests. This guide breaks down which species truly sleep, which just rest more, and how each one manages to survive winter.
As you read, you’ll pick up ways to spot a hibernator versus a light sleeper, what behaviors to look for, and the survival tricks squirrels use in the cold months.
Let’s dive in and see what’s really going on out there.
Which Squirrels Hibernate and Which Do Not
Most squirrels you spot in your yard stay active here and there during winter, relying on food they’ve stashed or short naps. Only a few ground-dwelling species actually hibernate for months at a time.
Ground Squirrels: True Hibernators
Ground squirrels like the Arctic ground squirrel and the thirteen-lined ground squirrel (Ictidomys tridecemlineatus) really hibernate.
They dig deep burrows in late fall, then drop their body temperature, heart rate, and metabolism for long stretches.
This state can last for months, depending on the weather and the species.
A few wild facts:
- Their body temperature can get close to freezing, especially in Arctic ground squirrels.
- Heart rates plummet from hundreds of beats per minute to just a handful.
- They survive off fat they packed on before hibernation and almost never leave the burrow until spring.
If you want details, ground squirrels start hibernating when food disappears and the soil gets cold. Their underground homes keep them safe from predators and nasty weather.
Tree Squirrels and Winter Dormancy
Tree squirrels—like Eastern gray squirrels (Sciurus carolinensis) and fox squirrels—don’t really hibernate.
Instead, they use torpor and food stashes to make it through cold spells, staying partly active all winter.
Here’s how they do it:
- They build dreys or use tree holes for insulation.
- They bury nuts and seeds all over (scatter-hoarding) and dig them up on warmer days.
- Torpor spells last hours or a couple of days, letting them save energy but still wake up to eat.
On milder winter days, you’ll probably see gray squirrels out, hunting for their buried snacks. Their noses and memories help them find food, and their nests shield them from the worst weather.
Flying Squirrels in Cold Weather
Flying squirrels don’t truly hibernate either.
They deal with cold nights, but their strategies differ from tree squirrels.
These little night gliders often huddle in tree cavities and nest together for warmth.
Key behaviors:
- Several flying squirrels pile into one cavity to keep from freezing.
- They mostly stay put during bitter cold but venture out to forage when it’s not so bad.
- They eat seeds, fungi, and whatever food they’ve managed to store for winter.
If you hear scurrying in your attic or walls in winter, flying squirrels or tree squirrels might be sneaking in for a warm spot—not hibernating underground.
How Different Types of Squirrels Prepare for Winter
Each squirrel species gets ready for winter in its own way.
How they prep determines if they’ll hibernate, use torpor, or stay active.
Some common steps:
- Ground squirrels fatten up and dig or expand their burrows. They line the chambers and seal up tunnels before settling in for hibernation.
- Tree squirrels gather and bury tons of nuts, then reinforce dreys or move into tree holes for shelter.
- Flying squirrels stash food and often share nests to keep each other warm.
You can tell who’s who by watching what they do: lots of digging and sealed burrows mean ground squirrels are hibernating. If you see squirrels burying nuts and foraging in daylight during winter, they’re probably gray or fox squirrels using torpor and food caches.
Winter Survival and Adaptations
Squirrels mix up their behavior and tweak their bodies to survive the cold.
Short-term torpor, nests, food stashes, and small body changes help both adult and baby squirrels get through winter.
Torpor Versus True Hibernation
Torpor means a short, reversible drop in activity and metabolism.
Tree squirrels go into torpor for a few hours or days during brutal cold. They slow down to save energy but wake up to eat or check on their young.
Ground squirrels and some chipmunks, though, hibernate for real.
True hibernators drop their body temperature way down and stay inactive for weeks or months, burning through fat stores.
If you spot a gray or red squirrel moving around on a mild winter day, it’s probably using torpor between snack runs.
Baby squirrels are more at risk; they need the nest and mom’s warmth instead of long torpor spells.
Nest Building and Shelter
Tree squirrels build dreys (those messy-looking leaf nests) or tuck themselves into hollow trees.
Dreys sit high in tree forks and use leaves, moss, and bark for insulation.
Cavities work even better for blocking wind, rain, and predators.
Flying squirrels usually pick tree cavities too, and sometimes share them to keep warm.
When natural sites run low, squirrels sneak into attics or wall spaces.
Baby squirrels stay in the nest until they can keep themselves warm, so mothers pick safe, insulated spots in late summer and fall to get ready for winter.
Food Storage and Fat Accumulation
Squirrels mainly use two food strategies: scatter-hoarding and middens.
Scatter-hoarders (like most tree squirrels) bury lots of little food stashes all over and rely on memory to find them.
Red squirrels go for middens—big, central food piles they guard fiercely.
These caches keep squirrels fed between torpor bouts.
Squirrels also fatten up in late summer and fall.
That fat helps true hibernators make it through months of sleep and gives tree squirrels energy for brief torpor and sudden cold snaps.
Baby squirrels depend on milk and mom’s care to build up their reserves before they ever leave the nest.
Physiological Changes: Body Temperature and Shivering
Squirrels slow their metabolic rate a bit during torpor, but they never hit the extreme temperature lows that true hibernators do. Tree squirrels might lower their body temperature by a few degrees just to save some energy.
Ground squirrels, on the other hand, can get shockingly cold—sometimes almost freezing. That’s a pretty wild change for such a small animal.
You’ll notice shivering right away when squirrels try to warm up. Their muscles start shaking to generate heat, especially after a torpor bout or if they’ve been out in the cold.
Because they’re small, squirrels lose heat fast. That’s probably why you’ll see flying squirrels huddling together or heading back to a cozy nest. It’s all about stopping that shiver and getting their body temperature back on track.
