Squirrels eat a lot of acorns and other seeds during the summer and fall to build up fat reserves to survive through the winter. They also make a cozy nest or cavity den (they don’t use your attic like raccoons) to protect them from predators and extreme temperatures.
You may have noticed large impressive nests high up in the trees this time of year or seen them digging deep into a tree trunk to store nut and berry shells for the winter months. Some people mistakenly assume that squirrels hibernate as they go into their nests, but that is not the case. While they do prepare for a long winter, they do not enter into true hibernation mode but rather a form of torpor.
Torpor is a state of low metabolic rate and body temperature that allows animals to conserve energy for periods when food and water is scarce. During torpor, an animal’s heart rate and breathing slow down but the animal is still capable of leaving their den for short periods to seek out buried food stores or search for shelter.
During the winter, squirrels spend most of their time in their drey nests. They are solitary creatures but will occasionally share their dens if it is too cold outside to sleep comfortably. Squirrels rely on the auto-response of shivering to maintain their core body temperature. This, combined with a thick fur coat and ample fat storage, is how they manage to stay warm throughout the freezing winter.