Squirrels are a common sight throughout the year, leading many to wonder how these small creatures endure colder months. As temperatures drop and food becomes scarcer, understanding their winter survival strategies is important.
Active or Dormant?
A common misconception is that squirrels hibernate through winter, much like bears. However, most tree squirrels, such as the eastern gray squirrel, do not truly hibernate. Instead, they enter periods of torpor, a state distinct from deep, prolonged hibernation. Torpor involves a temporary reduction in metabolic activity, including a lowered body temperature and heart rate, which helps them conserve energy during harsh weather. This state is temporary, allowing squirrels to awaken easily to forage.
True hibernation, seen in some ground squirrel species, involves a much deeper physiological shutdown that can last for months, with animals relying solely on fat reserves. Tree squirrels, by contrast, remain active throughout winter, though their activity levels are significantly reduced. They spend more time in their sheltered nests or dens during extreme cold, only venturing out on warmer, milder days to search for food.
Adapting to the Cold
Squirrels possess several adaptations that enable them to withstand winter’s chill. Their fur coat becomes thicker and denser as autumn progresses, providing a natural layer of insulation that traps heat close to their bodies. Their prominent bushy tails serve a dual purpose, acting as a blanket that squirrels can wrap around themselves, especially when curled up in their nests. Additionally, squirrels build up significant fat reserves during the fall by consuming large quantities of food, which provides both insulation and a crucial energy source when food is scarce.
Behaviorally, squirrels seek refuge in well-insulated homes. Tree squirrels construct nests known as dreys, typically spherical structures made from twigs, leaves, and moss, often found high in tree branches or within tree cavities. These dreys are effective at retaining warmth, with their interiors potentially being 20-30°C warmer than the outside air. In severe cold, multiple squirrels may huddle together in a single drey to share body heat, enhancing their survival chances.
Winter Foraging
A primary strategy for squirrels to secure food during winter is caching. Throughout autumn, they engage in “scatter hoarding,” burying individual nuts and seeds in numerous locations across their territory. This dispersal minimizes the risk of losing their entire food supply to other animals or if one cache is forgotten.
Squirrels do not rely solely on chance or smell to relocate these buried treasures. Research indicates they possess spatial memory, utilizing visual landmarks and a mental map of their environment to find their caches. Some squirrels employ a strategy called “chunking,” where they group similar food types in specific areas, which may aid in recall. When cached supplies become depleted, squirrels can turn to alternative food sources, such as tree buds, inner bark, pine cone seeds, or opportunistic scavenging from bird feeders and discarded human food.