Many people believe squirrels hibernate during the winter months, disappearing until spring. However, this is a common misconception for most familiar tree squirrel species. These agile rodents remain active throughout the colder season, navigating snowy landscapes and continuing their daily routines. Their ability to endure winter highlights their remarkable adaptations and survival strategies.
Why Squirrels Stay Active
Tree squirrels are not true hibernators. Unlike animals such as bears or groundhogs that enter a prolonged state of deep sleep, squirrels maintain a relatively stable body temperature year-round. They are endotherms, generating their own heat to sustain a warm internal temperature.
While they do not fully hibernate, squirrels can enter a temporary state of reduced metabolic activity called torpor. This allows them to lower their body temperature and heart rate for short periods to conserve energy during extreme cold or food scarcity. Squirrels can easily awaken from torpor, unlike true hibernators, enabling them to periodically forage for food.
How Squirrels Survive Winter
To cope with winter, squirrels employ a range of behavioral and physical adaptations. One significant strategy is food caching, storing food for later consumption.
Gray squirrels are “scatter hoarders,” burying individual nuts and seeds in numerous shallow holes across their territory. This method reduces the risk of losing their entire food supply. Red squirrels often practice “larder hoarding,” accumulating large piles of food, like green cones, in a central location called a midden, which they actively defend. Squirrels possess an acute sense of smell and strong spatial memory, allowing them to locate hidden caches even under snow.
Shelter is also crucial for winter survival. Squirrels construct insulated nests, known as dreys, in tree branches or cavities. These dreys, typically spherical and about the size of a football, are woven from twigs and leaves, then lined with soft materials for warmth. The interior of a well-built drey can be significantly warmer than the outside air.
During severe cold, squirrels may huddle together in a drey to share body heat. Squirrels also develop a thicker fur coat for winter, providing additional insulation. When foraging in snow, they rely on their sense of smell to find buried food and may shiver to generate heat if their body temperature drops.
The Ground Squirrel Exception
While tree squirrels remain active, many ground squirrel species exhibit a different winter strategy: true hibernation. Ground squirrels, unlike their arboreal relatives, spend most of their time below the soil surface, constructing extensive underground burrows. These burrows serve as their winter hibernacula.
During hibernation, ground squirrels enter a profound state of torpor where their metabolic rate drops significantly, and their body temperature lowers. They emerge from this deep sleep in spring when temperatures rise. This distinction highlights the varied survival adaptations within the squirrel family, with ground squirrels relying on prolonged dormancy to navigate the harsh winter months.