When autumn arrives, squirrels often appear noticeably larger, prompting questions about their fat accumulation for colder months. Squirrels do gain weight as winter approaches, as part of a broader survival strategy that helps them endure periods of scarcity and low temperatures.
The Purpose of Winter Fat
The fat squirrels accumulate serves as an energy reserve for their survival during winter when food sources become scarce and temperatures drop. This stored energy fuels their metabolism, enabling bodily functions even when foraging is difficult. The fat also provides insulation, helping them maintain a stable body temperature in freezing conditions.
Squirrels convert the food they consume into fat through metabolic processes. This stored energy generates heat and sustains them during periods of inactivity or when they are unable to find food. For some species, specialized brown adipose tissue, or brown fat, plays a role in generating heat rapidly, particularly during periods of arousal from torpor or hibernation.
How Squirrels Prepare for Winter
Squirrels engage in several preparatory behaviors as seasons shift into autumn, with fat accumulation being a key aspect. They significantly increase their food intake, consuming large quantities of nuts, seeds, and other edibles to build up their fat reserves. This period of increased consumption is observable as their bodies become noticeably plumper.
Beyond gaining weight, squirrels are renowned for their food caching behaviors. Eastern gray squirrels, for example, engage in “scatter hoarding,” burying individual nuts and seeds in numerous shallow pits across their territory. They rely on a combination of memory and their acute sense of smell to locate these hidden stashes later, even under snow. This cached food serves as a primary energy source throughout the winter, complementing their stored body fat.
Squirrels also prepare or find insulated shelters to conserve energy and escape the cold. Tree squirrels often build or reinforce nests, known as dreys, in tree branches, or utilize natural tree cavities. These dens are constructed from leaves, twigs, and other plant materials, providing a cozy environment that can be significantly warmer than the outside air. Some species may even share these dens to benefit from communal body heat during severe cold.
Diverse Winter Strategies Among Squirrels
Not all squirrels employ the same winter survival strategies, and their reliance on fat accumulation varies significantly depending on their species and behavior. Tree squirrels, such as the eastern gray squirrel, do not enter a state of true hibernation. They remain active throughout the winter, venturing out on warmer days to access their cached food supplies. For these species, fat reserves are important for insulation and providing short-term energy during extreme cold, but their primary survival mechanism is their stored food.
In contrast, many species of ground squirrels, including marmots, are true hibernators. These animals rely heavily on extensive fat accumulation to sustain them through months of deep sleep. They can sometimes double their body weight in the autumn, with this fat fueling their bodies as their metabolic rate slows dramatically during hibernation.