Winter Adaptations

As I deal with a pair of winter storms over the course of writing this blog, I am sitting cozy and warm inside my house. How do animals, who don’t live in houses with central heating or furnaces make it through the winter? Some migrate to warmer areas, but those that stay behind have special adaptations that help them cope with the cold and snowy weather.

Many animals go into mega energy conservation mode during the winter because not only do they lack heating systems for their homes, they also lack supermarkets that carry a reliable food source. For herbivores, their plant-based food supply is either dormant (and not producing the nutritious shoots they crave), or buried under snow and ice. Whether warm-blooded or cold-blooded, both need to keep warm to survive. Cold-blooded critters rely on the sun’s radiant heat to stay warm, and this is a challenge when it’s cold outside and the sun isn’t reliable. Warm-blooded critters metabolize food to stay warm- they eat much more than cold-blooded ones. One option to keep up metabolism is to spend energy to search for scarce food. But there are other ways to get by.

Hibernation is probably the first coping mechanism you think of, and it’s quite common in the mammal world. Bears do it, bats do it. What is it, compared to normal sleep? When you go to sleep your body slows down. Breathing and heart rate go down and metabolism slows, and your body temperature cools a bit. Hibernation is an extreme version of this. But to be asleep for weeks or months on end requires quite a bit of sustaining energy, even if bodily functions slow to the point of nearly stopping. That’s why bears go on a feed frenzy each fall, gorging themselves on spawning salmon or high-energy moths if they live in the right place.

NPS graphic of a hibernating bear

For those that don’t hibernate, finding food is a priority. Arctic foxes and snowshoe hares both grow a white coat for snow camouflage. The fox uses its camo to hunt; the hare uses its to avoid being eaten. The bison uses its large head as a snowplow to uncover buried vegetation. Ever wonder what that large hump at its shoulder is? Extra muscles to support all that head.

Snowshoe hare (Montana Fish, Wildlife, and Parks)

Bison plowing for food (NPS)

Preserving body heat is a great way to maximize caloric efficiency. The thick fur coat of a muskox traps body heat. Blubber insulates whales, seals, and walruses. Polar bears have black skin that absorbs heat, and their fur traps heat, including body heat that they radiate.

Walruses (US Fish and Wildlife Service)

Ease of mobility is also an efficiency adaptation. Lynxes and caribou both have large feet that act as snowshoes, making it easier to get around so they burn fewer calories doing so.

Check out the foot on that lynx! (Natural Resources Research Institute)

These are just a few of the many adaptations that make survival possible for warm-blooded mammals. There are others, and there are also adaptations for cold-blooded animals (like a frog with antifreeze in its blood) and plants too! Enjoy your heater for the rest of the winter!