As winter approaches, squirrels adapt to colder temperatures and scarce resources. Their ability to endure winter stems from behavioral and physiological adaptations.
Winter Survival Strategies
Squirrels employ strategies to survive winter, focusing on food acquisition and maintaining body temperature. Many species engage in scatter hoarding, burying individual food items like nuts and seeds across their territory. This allows them to retrieve provisions later when natural food sources are scarce, preventing reliance on a single, vulnerable cache.
Activity levels shift as temperatures drop, with squirrels becoming less active during coldest periods. While most tree squirrels do not truly hibernate, they may enter torpor, a state of reduced metabolic activity. During torpor, their body temperature and heart rate decrease, conserving energy for short durations, allowing them to emerge and forage on warmer winter days.
To stay warm, squirrels develop a thicker winter coat, providing enhanced insulation. They also increase their metabolic rate, generating more internal heat. When temperatures are extremely low, huddling together in shared nests helps conserve body heat.
Their Winter Shelters
During winter, squirrels seek secure, insulated shelters from harsh weather and predators. One common shelter is a drey, a nest typically constructed in tree branches or dense foliage. Dreys are spherical structures woven from twigs, leaves, moss, and other plant materials, often lined with softer elements like shredded bark or fur for insulation. These elevated nests provide a dry, warm retreat above the snow line.
Squirrels also utilize natural tree cavities, hollows within tree trunks or large branches. These offer excellent protection due to their enclosed nature and the insulating properties of the surrounding wood. They provide a stable, protected environment against wind, rain, and snow.
Some squirrel species, particularly ground squirrels, construct burrows beneath the earth. These underground tunnel systems provide consistent temperatures, shielding occupants from extreme cold. Burrows can be complex, with multiple entrances and chambers, offering secure spaces for resting and storing food caches.
Species-Specific Winter Behaviors
Winter behaviors vary between tree squirrels and ground squirrels. Tree squirrels, such as grey and red squirrels, generally remain active throughout the winter. They rely heavily on cached food supplies to sustain them when fresh foraging is difficult. While they may spend more time in insulated dreys or tree cavities during severe weather, they do not enter prolonged hibernation.
Ground squirrels, including species like chipmunks, marmots, and groundhogs, undergo true hibernation, a long-term state of inactivity and metabolic suppression. During hibernation, their body temperature drops significantly, heart rate slows, and breathing becomes very shallow. They typically rely on stored body fat accumulated during warmer months to sustain them through this extended dormancy.
Unlike tree squirrels, ground squirrels often retreat to their underground burrows for the entire winter, emerging only when temperatures rise in spring. This allows them to conserve energy and survive periods of extreme cold and food scarcity without needing to forage.