Many people wonder about squirrels during colder months, often assuming these creatures disappear into a long winter sleep. The sight of fewer squirrels scampering through snow-covered landscapes prompts questions about their winter habits and how they survive when temperatures drop and food becomes scarce.
The Definitive Answer
Most tree squirrels, such as the eastern gray and red squirrel, do not truly hibernate during winter. True hibernation involves a prolonged state of deep inactivity where an animal’s body temperature, heart rate, and metabolic rate significantly decrease. Unlike true hibernators, squirrels maintain a relatively constant body temperature throughout the year.
A Winter Slumber: What Squirrels Actually Do
Instead of true hibernation, tree squirrels engage in a state known as torpor, a temporary reduction in activity and metabolism. During torpor, their body temperature, heart rate, and breathing slow down, but not to the extreme levels seen in hibernating animals. This state helps them conserve energy during periods of extreme cold or food scarcity, typically lasting from a few hours to several days. They can easily awaken from torpor to forage for food, particularly on milder winter days.
Squirrels also prepare for winter by building insulated nests, known as dreys, in tree branches or cavities. These dreys, constructed from twigs and leaves, offer warmth and shelter from the elements. During the coldest periods, multiple squirrels may even share a drey to benefit from shared body heat.
Survival Strategies
Squirrels adopt specific strategies for winter survival that differ from full hibernation. They prepare by caching food, collecting and burying nuts, seeds, cones throughout autumn to create reserves for winter. Eastern gray squirrels, for example, scatter-hoard their food, burying individual items in numerous shallow holes. They rely on both memory and a keen sense of smell to locate these hidden stashes, even under snow.
Additionally, squirrels consume extra food in the fall to build up fat reserves, providing energy and insulation during colder months. Their thick fur coats also grow denser in winter, providing natural insulation. When temperatures are particularly frigid, they may shiver to generate internal heat, a common physiological response to cold. These adaptations allow them to remain active year-round, emerging from their dens to access food even when conditions are challenging.
Different Squirrels, Different Winters
While most tree squirrels, like the eastern gray squirrel and red squirrel, do not hibernate, some ground squirrel species do engage in true hibernation. This distinction can lead to common confusion about squirrel winter behavior. Ground squirrels typically dig sloped burrows for their winter slumber, where they can hibernate for several months.
Unlike tree squirrels, which frequently emerge from their dens, hibernating ground squirrels experience a deeper, longer period of dormancy, with their body functions significantly reduced. Tree squirrels, by contrast, are seen throughout the winter, albeit with reduced activity during severe weather. Their ability to remain active and access cached food differentiates their winter survival from the deep, prolonged sleep of their ground-dwelling relatives.