Animals demonstrate a variety of ways to deal with winter. Their behaviors, the size and shape of their bodies, or the way that their bodies work can be adaptations to dealing with the cold that characterizes winter in northern climates. In most cold places, snow plays a large part in shaping winter conditions, and many animals also exhibit adaptations specifically for success in snowy environments.
There are three main ways that animals deal with winter:
Migration refers to a regular, seasonal movement pattern between different locations. The most-well known migrants are birds. Many birds that live in mountainous and northern regions of North America during the summertime spend their winters in warmer locations further south. When it is cold in Alaska, for example, the Yellow Warbler is in Central America. Migration can be an advantage because the birds don’t have to use extra energy staying warm and because foods such as insects are more abundant closer to the equator during the winter months in Alaska. Because summer days in Alaska are long and there is a burst of plant and insect life, it is worth it for the Yellow Warbler to spend the energy to fly thousands of miles back to Alaska to breed and raise its young. The boreal forest of interior Alaska has been called a “bird nursery” for this reason.
Some mammals in North America migrate, too, although they don’t travel as far as many birds. The best example are certain caribou herds of Alaska and northern Canada. Some herds, such as the Western Arctic Caribou Herd and the Porcupine Caribou Herd travel hundreds of miles in a year. They give birth to their young on the northern tundra, where ocean breezes keep pesky insects away and where nutritious grasses grow in the 24-hour sunlight. In the winter, they move to more sheltered, forested areas, where the lack of strong winds means that snow is softer, and they are better able to dig in through it to get to food sources such as lichen.
Migration is an example of a behavioral adaptation. Usually, the migratory behavior that we observe is partly learned from others and partly enabled by physiological traits such as an internal compass and hormones that take cues from changing light conditions.
Hibernating is another way that animals can avoid dealing with the challenges of winter in cold, snowy climates. Bears are the most famous hibernators in North America, but other animals such as marmots and ground squirrels hibernate, too.
During hibernation, an animal’s heartbeat, breathing, and body temperature drop, which means it doesn’t have to use as much energy just to keep its body warm. By conserving energy, the animal doesn’t need to take in as much energy in the form of food to stay alive. That is very helpful in snowy places, where the plant leaves, roots, seeds, and berries that make up a large part of hibernating mammals’ diet are covered under a deep blanket of snow for six to nine months of the year.
Hibernation is a behavioral adaptation and a physiological adaptation. In order to hibernate, an animal’s body must be able to survive with a lowered heart rate, breathing rate, and body temperature for months at a time.
For some animals, the best strategy for surviving winter in cold, snowy climates is to stay where they are and keep going about the activities of their daily lives. In Alaska, most mammals stay active all winter long. Some birds stay in Alaska all year instead of migrating. Animals that stay active during cold, snowy winters need to be able to find food, water, and shelter without the benefits of grocery stores, indoor plumbing, and heated buildings.
Animals that stay active in Alaska and other areas where snow stays on the ground for months at a time have special physical, physiological, or behavioral characteristics that allow them to be successful in snowy environments.
Select the topics below to learn about some of the ways in which northern animals are adapted to life in the snow.