Squirrels are a familiar sight, and their year-round activity often prompts questions about their winter survival. This article explores how squirrels adapt to the challenges of cold weather.
Do Squirrels Hibernate?
Whether squirrels hibernate depends on the specific type. Some species, particularly ground squirrels, are true hibernators, entering a prolonged state of inactivity for months, significantly reducing their metabolic functions. However, commonly observed tree squirrels, such as gray and red squirrels, do not engage in true hibernation. These tree-dwelling squirrels remain active throughout the winter, although their activity levels may decrease during periods of severe cold. Tree squirrels employ a different strategy for winter survival, involving intermittent periods of reduced activity. They do not undergo the deep, sustained metabolic shutdown characteristic of true hibernation, instead relying on behavioral and physiological adjustments to cope with freezing temperatures and limited food availability.
Different Winter Survival Strategies
Animals employ distinct physiological strategies to endure the winter, with true hibernation and torpor being two primary methods. True hibernation is a prolonged state of metabolic depression, lasting weeks or even months. During this deep sleep, an animal’s body temperature drops significantly, and its heart rate and breathing slow considerably. For instance, the heart rate of a hibernating ground squirrel can decrease from 200-300 beats per minute to a mere 2-4 beats per minute.
Animals like groundhogs and some ground squirrels, including the Arctic ground squirrel and 13-lined ground squirrel, are true hibernators, surviving extended periods without food or water solely on fat reserves. These hibernators periodically warm their bodies for brief periods before re-entering a torpid state, a process that helps maintain brain health.
In contrast, torpor is a shorter-term state of decreased physiological activity. It involves a reduced body temperature and metabolic rate but is less extreme and typically lasts from a few hours to several days. Unlike true hibernators, animals in torpor can easily awaken and often do so to forage for food, particularly during warmer spells. This is the primary strategy utilized by tree squirrels, allowing them to conserve energy during cold conditions while still being able to access their food caches. The ability to enter and exit torpor frequently provides flexibility in responding to fluctuating winter conditions.
Preparing for the Cold Months
Squirrels undertake a series of diligent preparations to increase their chances of surviving the cold months. One primary activity is food caching, where they gather and store an abundance of nuts, seeds, and acorns. Tree squirrels commonly engage in “scatter hoarding,” burying individual food items in numerous locations across their territory. This strategy minimizes the risk of losing their entire food supply to competitors or environmental changes.
Their impressive spatial memory and keen sense of smell help them locate these hidden stashes later in the winter. Some squirrels also practice “deceptive caching,” pretending to bury food in one spot to mislead observers before burying it elsewhere.
Beyond food, squirrels meticulously prepare their shelter. They construct or reinforce nests, known as dreys, typically high in tree branches, using twigs, leaves, and moss for insulation. Alternatively, they may utilize existing tree cavities or burrows, which offer enhanced protection from the elements. These dens provide a warm, secure environment, sometimes shared by multiple squirrels to conserve heat, particularly during severe cold.
Before winter fully sets in, squirrels also consume additional food to build up fat reserves. This accumulated fat provides both insulation and a vital energy source to sustain them through periods when foraging is difficult.