Start Shivering...

 Since we're not
 covered with a warm
 fur coat, how do humans
 adjust to the cold?

 » Read More

When winter hits and food becomes scarce, animals have three choices: migrate, hibernate or resist.

Migrating seems like an obvious choice-you just move to where it's warmer. Of course, this requires a lot of energy and there are a lot of risks involved. A long journey can expose you to predators and bad weather. A lot of animals just aren't cut out to move long distances - you don't see lots of frogs migrating to Florida every fall. For many animals, hibernation and resistance may be better strategies.

Black Bear

Hibernating animals find a den and live off of their stored energy (fat) for the winter. (Don't try this at home - you have to go to school). Most of these animals slow their heartbeat and breathing way down during the winter. This conserves the stored energy they're using. But few of these animals sleep straight through the winter. Instead they get up once in a while and re-warm themselves. Even though hibernation saves a lot of energy, these animals still need a lot to get through the winter. That means they have to store plenty of fat before the cold arrives. For animals that can't eat enough or store enough to make it through the winter hibernating, resistance is the last choice.

Weasel in winter

Wildlife can't go the store and buy more fur, or rent a space heater. But they have evolved many ways to resist the cold. Some insects produce anti-freeze to keep their body fluids from freezing; small mammals travel under the snow to stay warm and protected; large mammals and birds shift what they eat to take advantage of what's available in winter. They all have one thing in common-trying not to become a popsicle.

When it comes to heating their bodies, animals fall into two groups: endotherms, who produce their own heat; and, ectotherms, who can't make their own heat - their bodies are the same temperature as their surroundings.

Some people call endotherms "warm-blooded animals." This group includes mammals (like us) and birds. Ectotherms are sometimes called "cold-blooded animals." This group includes insects, reptiles and amphibians. Read on to find out how endotherms and ectotherms find heat, or ways to do without it, in winter.

Winterize Your Backyard Habitat!
Can we help some of our local wildlife have an easier winter? Animals who resist winter need high-energy food, a reliable water source and shelter. You can help them by planting shrubs that provide food in the winter; or even build a brush pile that could provide shelter for small mammals, turtles, salamanders and insects. Check out the National Wildlife Federation's suggestions for improving your backyard habitat for winter in the Other Lynx section.