Each morning when I go out and brush the snow off my car, the temperature seems to be a little colder. As humans, we heavily rely on our layers and puffy coats to keep us warm. It’s not uncommon to have a base layer, fleece, light puffy, shell, and big puffy while outside. But the animals around us don’t have extra jackets or gloves for when the temperature drops. To survive winter, some animals hibernate or migrate while other animals stick around and tough it out. The animals who stay have adapted to survive the winter months; some of these changes are behavioral and some are physical.
First it seems reasonable to ask how animals lose heat in the first place. The process of heat transfer can occur through conduction, evaporation, convection, and radiation. Conduction is when the animal’s skin, fur, feathers, and feet are touching the cold snow, or direct solid to solid contact. Convection, however, occurs when the animal’s skin, fur, feathers, and feet are touching the cold air. Both of these methods of heat loss are constantly happening because animals are constantly outside, where there is nothing but cold air and snow. Additional heat loss occurs through variably through radiation and evaporation, depending on time spent in shade or sun, breathing rates, and energy being used. Animals can also gain heat through radiation, especially on some of our high altitude sunny days. An animal’s varying energy levels can mean the difference between life and death in a cold climate.
Most animals who stick around for the winter slow their metabolism as a means of conserving energy. Slowing their metabolism requires less food intake, so less energy is needed to sustain their bodies. This helps the animal survive in harsh conditions and enables them to use their valuable energy in more efficient ways. They are able to survive on less food, which is also helpful because of the decrease in food availability. Some animals, like the ptarmigan, even change their digestive tract completely so that they can better digest the twiggy dry foods available to them in the winter! Every animal has an energy budget, and it takes energy to stay warm. And like any budget, animals can only can take out what they put in. So when food is scarce, that means there’s little energy available. This is why other adaptations like growing winter coats, and other methods of keeping warm, are essential to their survival.
When asked about how animals adapt to conserve energy in the winter, most of us think of fur first. This response seems natural considering our first response as humans when we’re cold is to add layers. Most animals in the winter months thicken their fur or plumage. A thicker coat means less conduction and less convection, therefore less heat is lost. This adaptation requires very little energy and helps animals conserve what would be lost warming their bodies. Some animals who thicken their coats around here include moose, ermine, snowshoe hare, ptarmigan, and bobcat.
So whether you’re brushing snow off your car or enjoying a powder day up on the mountain, be thankful for your layers and puffy coats! Because at the end of the day, all of the animals in our backyard have a goal quite similar to ours: to stay warm, save energy, and survive and thrive in these cold winter months.
Brooke Friesen is a naturalist at Walking Mountain Science Center. She enjoys seeing the local wildlife on moonlight snowshoe hikes and climbing tall things. Come visit her at our campus in Avon or atop Vail Mountain at the Nature Discovery Center!
