The sight is a familiar one: a squirrel dropping a nut or acorn into a hole to store it for the coming winter (thus the phrase “squirreled away”). But if a squirrel isn’t squirreling away food in the colder months, what exactly is it doing?

Given the number of squirrel species—more than 200—and the fact that these rodents have established themselves in just about every natural environment, it’s difficult to make generalizations about them. However, most squirrels spend the warmer months hoarding food, getting plump and building shelters. In other words, the squirrel’s lifecycle hinges on surviving winter. Studies show that the adult gray squirrel, for example, eats almost its own weight (one to one and a half pounds) each week during the peak months of activity in order to store fat for winter.

What do squirrels do in the winter? Do squirrels hibernate?Tree squirrels are most active during daylight hours. Some squirrels are early risers, but others such as the eastern gray squirrel prefer sunset to sunrise. During the winter, however, all squirrels tend to become idle and typically stay in their nests. Most species of ground squirrel, including the Arctic ground squirrel of Alaska, hibernate and are inactive throughout the winter months.

Tree squirrels don’t hibernate though they seem more scarce during the winter. Look in the hollow of a tree or scan its bare branches for masses of leaves and twigs (called dreys) and you might spot a wintering squirrel family. As long as temperatures stay above freezing and no snow or sleet is falling, tree squirrels may still be seen climbing trees and retrieving scattered food stores.

The two most common tree squirrel species in the United States, the eastern gray squirrel and the reddish-brown fox squirrel, have both a summer and a winter breeding season. December and January are the most active months for winter tree squirrel mating. Most winter squirrel litters are relatively small (two to five young) and arrive in March. Tree squirrels mature slowly and, in some cases, may share their parents’ den even after the first year. 

Where do squirrels live in the winter?After spending most of the warmer seasons fattening up for the winter, squirrels tend to stick to their nests during the colder months.

Of course, it’s not uncommon to hear a clambering across the roof that’s sometimes followed by scratching and squeaking in the attic. This could be evidence of squirrels or another pest. Squirrels are diurnal, no matter the time of year, so if you hear noise during the day, you’re probably playing host to squirrels rather than rats or raccoons.

But why the attic? There a number of factors: the availability of other habitats, the size of the squirrel population, whether the squirrels are in one of their mating seasons, cold temperatures, the presence of squirrel predators in the area, and the accumulation of food tempting to squirrels on or around your roof.

Regularly cleaning your gutters of acorns, nuts, pinecones and leaf litter can be a good way to make sure squirrels stick to the trees rather than your attic. 

If you suspect your attic is home to squirrels for the winter, do not try and remove them yourself. Remember, they are still wild animals, and you should contact a pest management professional immediately.