Squirrel activity in winter varies significantly by species and environmental conditions. While some remain active, others use dormancy strategies to survive. These diverse approaches highlight how squirrels adapt to seasonal challenges.
Winter Activity Patterns
Many common tree squirrel species, such as the Eastern gray squirrel, remain active during winter. Their activity levels are reduced compared to warmer seasons, and they spend more time in nests during extremely cold periods to conserve energy and stay warm.
In winter, squirrels are most active during early morning and late afternoon, foraging for stored food. Factors such as temperature, snow cover, and the availability of their food caches influence how frequently they venture out. Their reduced outdoor activity and reliance on stored resources indicate winter presents significant challenges.
Survival Adaptations
Squirrels that remain active during winter rely on adaptations to endure the cold and scarcity of food. A primary strategy involves extensive food caching during autumn, where they bury nuts, seeds, and other edibles. This caching can involve “scatter hoarding,” hiding individual items in many locations, or “larder hoarding,” storing larger quantities in one or two main spots. Gray squirrels often use scatter hoarding, while red squirrels might create larger caches called middens.
Their ability to retrieve these hidden stashes is supported by spatial memory, allowing them to remember cache locations even under snow. Some research suggests they use a cognitive strategy called “chunking,” organizing similar food types in specific areas to aid recall. Physiologically, squirrels prepare by accumulating body fat in the fall, which serves as an energy reserve and provides insulation.
Their thick fur coats offer natural insulation, and they can fluff their fur to trap more heat. Shivering is another mechanism they use to generate body heat. For shelter, they construct insulated nests, known as dreys, from twigs and leaves, often in tree cavities or forks of tall trees. These dreys can be significantly warmer than the outside air, and squirrels may share them to benefit from communal body heat.
Divergent Winter Lifestyles
Squirrels encompass species with distinct winter survival strategies, primarily differentiating between tree squirrels and ground squirrels. Tree squirrels, like gray and red squirrels, remain active throughout winter. They do not truly hibernate but may experience short periods of torpor during severe cold snaps. Torpor involves a temporary lowering of body temperature and heart rate to conserve energy, allowing them to wake periodically to forage.
Many ground squirrels, including chipmunks and marmots, are true hibernators. Hibernation is a prolonged state of deep dormancy lasting several months, where body temperature, heart rate, and breathing drop significantly. They rely on fat reserves accumulated during warmer months. While mostly asleep, some may briefly awaken to consume stored food or eliminate waste. Ground squirrels typically hibernate in burrows, providing stable temperatures and protection.