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Mammals: Polar Bear

Range: along the coasts and inland streams and lakes of Alaska and Canada in North America, Greenland, Norway, and Russia Habitat: arctic, tundra, and woodlands

Baby, it’s cold outside!

Polar bears live on ice and snow, but that’s not a problem—these bears have some cool ways to stay warm!

Hair— A dense, thick undercoat of fur is protected by an outer coat of long guard hairs that stick together when wet, forming a waterproof barrier to keep them dry. Even though polar bears look white, their hair is really made of clear, hollow tubes filled with air.

Blubber— Blubber helps insulate polar bears from the freezing air and cold water, and acts as a nutritional reserve when food can’t be found. This blubber also helps the bears float in the water. It is 2 to 4 inches (5 to 10 centimeters) thick.

Winter Sleep— When the temperature outside drops, many bears stay warm by making a den and sleeping. Polar bears do not hibernate, but their body functions do slow down at this time. Many scientists call this “winter sleep,” because the bears can easily be awakened. A mother polar bear can give birth and nurse her young while still in her winter sleep.

What’s on the menu?

Polar bears are mainly meat eaters, and their favorite food is seal. They will also eat walrus, caribou, beached whales, grass, and seaweed. Polar bears are patient hunters, staying motionless for hours above a seal's breathing hole in the ice, just waiting for a seal to pop up.

Unfortunately, many bears have learned to eat at garbage dumps. They could be injured or poisoned by trash, and it puts the bears in close contact with humans. This can be a dangerous situation for both humans and bears!

Polar bears at the San Diego Zoo get a ground-meat diet made for carnivores, dog kibble, trout and other fish, as well as root vegetables and lettuce. Cow femur bones and thawed rabbits are added once or twice per week.

Noses with legs

The polar bear's nose is so powerful it can smell a seal on the ice 20 miles (32 kilometers) away, sniff out a seal's den that has been covered with snow, and even find a seal's air hole in the ice up to one mile (1.6 kilometers) away. No wonder many people call them "noses with legs!"

Den mothers and cubs

For such a big animal they sure start out small! A cub is about the size of a rat when it is born. The mother bear digs a cozy den in the snow to have her cubs. The den is no bigger than a telephone booth, but it can be about 40 degrees warmer in there. Usually two cubs are born to each mother between December and January. They are hairless and blind at birth, and depend on their mother to keep them warm and fed.

Milk from polar bear mothers is 35 percent fat, the richest milk of any bear species. This helps the cubs grow quickly, and by April they weigh more than 20 pounds (9 kilograms) and start exploring with their mother outside the den. At about two years of age they are ready to be on their own.

Who's the biggest?

Both polar bears and brown bears are big, and are the largest land carnivores. But most experts agree that polar bears are the tallest bears, getting up to 10 feet (3 meters) long.

What about the future?

For a while, polar bears were in trouble. People killed them just for trophies, and they were losing some of their wild places to live as people started moving into their territory. Global warming has affected polar bears as well, as ice sheets are melting, preventing the bears from traveling in search of food. Many countries got together to help this magnificent bear by preserving its habitat and setting up hunting restrictions. Polar bears still need our help. People must continue to give these bears large, safe places to live, and try to keep the environment clean and free of pesticides that could poison the bear's food.