How Do Animals Survive the Winter?
By Marilyn Shy, Kalkaska Conservation District
Winter has now fully arrived. The days are short and the nights are long. Temperatures rarely get above freezing, and there is snow outside the windows. But where we are able to sit by the fire and enjoy a hot cup of cocoa, put on an extra sweater, or grab another blanket, animals are not so lucky.
What DO animals do to survive these harsh conditions?
We know that bears sleep for most of the winter, and many birds fly south. Hibernation and migration are two strategies used by animals in northern latitudes which enable them to survive the most brutal days and nights that Mother Nature doles out.
But what about all the other animals out there? Muskrats, beavers, tree squirrels, raccoons, mice, voles, deer, opossums, skunks? It’s amazing to think about how each of these animals has evolved in different ways in order to survive and thrive.
Let’s take beavers, to start. These animals have special adaptations including glands that secrete oils that help them to waterproof their fur. They also store extra fat in their tails and use it for energy, depleting their stores as winter progresses. Winter is also an important time in the reproductive cycle for beavers. They typically mate in January or February with the females giving birth to a litter of kits between April and June.
Opossums also stay active during the winter. However, as the temperatures drop, they spend more time in their dens. Opossums often find shelter in burrows that were originally created by other animals. They rarely dig new burrows. Other spaces where opossums seek shelter include: buildings and homes, logs and trees, rock crevices, and wood piles. Opossums will try to make these places as warm as possible, which means lining their nests with grass and other soft and insulating materials. They gather this material and transport it either in their mouths, or hold a bundle and transport it with their prehensile tails.
Similar to opossums, skunks stay in their dens during cold snaps and harsh weather. But they have another method to help them stay warm. Because of their gentle nature, skunks can spend the winter in groups of a dozen or more! This makes surviving easier when there is heat to share. Opossums rarely share their nest with other opossums.
Unlike many rodents and birds which hoard food for the cold months, the skunk will have spent the fall eating as much as possible so it can stay warm during its mid-winter dormancy. This binge eating creates thick layers of fat underneath its skin, a winter jacket of sorts. Settled into its den, the skunk will become dormant, but does not enter a full state of hibernation. Instead, skunks enter a state of torpor----a sort of deep sleep from which they awake from time to time. By the time February or March rolls around, skunks emerge from their dens to find mates. After breeding, both males and females seek to rebuild fat reserves, having lost, on average, about 30 percent of their body weight during the winter.
Lastly, let’s look at deer, animals we still see frequently although perhaps not as much as in other seasons. This is because deer decrease their activity levels in order to conserve energy. They also change their diet, adding high calorie foods like fruit and nuts to their normal diet of twigs, stems and grasses. Like many other animals, their bodies retain more fat in the fall. They grow a new, thicker coat that better insulates them in cold weather. Their winter coats contain longer, thicker, darker fur, called guard hairs. These hairs absorb more sunlight and trap body heat more efficiently.
In some ways, we can think about what animals do to survive the winter as not that much different from what humans do. We eat more, sleep more, and put on extra clothes (or extra fur), and somehow, some way, we make it through the dark sunless days until we reach the spring. Sadly, mortality rates for creatures in the wild can still be high during the most difficult winters. But in general, animals emerge, as we do, ready to greet a new season of rebirth and renewal. It can’t be that far off, can it?