The polar bear, or "Nanuuq," as the Eskimos call it, lives only in the Northern Hemisphere, on the arctic ice cap, and spends most of its time in coastal areas. Polar bears are widely dispersed in Canada, extending from the northern arctic islands south to the Hudson Bay area. They are also found in Greenland, on islands off the coast of Norway, on the northern coast of the former Soviet Union, and on the northern and northwestern coasts of Alaska in the United States.

Some polar bears may make extensive north-south migrations as the pack ice recedes northward in the spring and advances southward in the fall. They also may travel long distances during the breeding season to find mates, or in search of food.

The polar bear is the largest member of the bear family, with the exception of Alaska's Kodiak brown bears, which equal polar bears in size. Males stand from 8 to 11 feet tall and generally weigh from 500 to 1,000 pounds, but may weigh as much as 1,400 pounds. Females usually stand 8 feet tall and weigh 400 to 600 pounds, but may reach 700 pounds. Part of the reason the polar bear weighs so much is that is stores about a 4-inch layer of fat to keep it warm.

The polar bear has a longer, narrower head and nose, and smaller ears, than other bears.

Although the polar bear's coat appears white, each individual hair is actually a clear, hollow tube which tunnels the heat of the sun's rays to the bear's skin and helps it stay warm. Some of the sun's rays bounce off the fur, making the polar bear's coat appear white. During the summer months, adult bears molt, or gradually shed their coats and grow new ones, which look pure white. By the following spring, the sunshine has caused their coats to turn a yellowish shade. Polar bears also sometimes may have a yellowish shade to their coats caused by staining from seal oils.

The polar bear's coat helps it blend in with its snow- covered environment, which is a useful hunting adaptation. The polar bear's front legs appear slightly bowl-legged and pigeon- toed, and fur covers the bottoms of its paws. These adaptations help the polar bear keep them from slipping on ice.

Because the polar bear rarely eats vegetation, it is considered a carnivore, or meat-eater. The ringed seal is the polar bear's primary prey. A polar bear may stalk a seal by waiting quietly for it to emerge from its blow hole or "atluk," an opening seals make in the ice allowing them to breathe or climb out of the water to rest. The polar bear will often have to wait for hours for a seal to emerge. Because the polar bear's coat is camouflaged against the whiteness of the ice and snow, the seal may not see the stalking bear. Polar bears eat only the seal's skin and blubber, or fat, and the remaining meat is an important food source for other animals of the Arctic. For example, Arctic foxes feed almost entirely on the remains of polar bear kills during the winter.

Polar bears also prey on walrus, but, because of the walrus's ferocity and size, bears are usually only successful preying on the young. The carcasses of whale, seal, and walrus are also important food sources for polar bears. In fact, because of their acute sense of smell, polar bears can sense carcasses from many miles away.

Polar bears can run quite swiftly, but are most agile in the sea. They are excellent swimmers, and can reach speeds of up to 6 mph in the water. They are good divers, too. When being pursued by hunters in open water, polar bears have been known to escape by plunging 10 to 15 feet below the surface and resurfacing a good distance away. They also have been seen swimming up to 100 miles away from ice or land.

Polar bears reach breeding maturity at 3 to 5 years of age. Males may travel great distances in search of female mates. While breeding usually takes place in April, like other bears, the embryos may not implant (develop) until the following year, depending on whether the mother has had a stable enough supply of food to sustain herself as well as the developing cubs through the winter.

In October and November, male polar bears begin to head out on the pack ice where they spend the winter. Pregnant females, however, seek sites on the mainland or on sea ice to dig large dens in snow where they will give birth and spend the winter. The temperature inside the polar bear's den can be up to 40 degrees warmer than outside. Usually two cubs are born in December or January. When the cubs first arrive, they are blind, hairless, and no bigger than squirrels. However, the cubs grow rapidly from the rich milk provided by their mother.

As soon as spring comes, the mother bear leads her cubs to the coast along the open sea, where seals and walrus are abundant. The mother will fiercely protect her cubs from any perceived danger. The cubs remain with their mother for 2 1/2 years. Because of this, most adult female polar bears breed only every third year.

Polar bears have traditionally played an important role in the culture and livelihood of Eskimos and other Native people of the North. They depend on the animals for food and clothing.

In the United States, polar bears are a federally protected species under the Marine Mammal Protection Act of 1972. This protection prohibits hunting of polar bears by non-Natives and established special conditions for the importation of polar bears or their parts and products into the United States. Eskimos and other Alaska Natives are allowed to harvest some polar bears for subsistence and handicraft purposes. The U.S. Fish and Wildlife Service is the federal agency responsible for managing polar bears under the Marine Mammal Protection Act.

An international conservation agreement for polar bears signed in 1976 by the United States, the former Soviet Union, Norway, Canada, and Denmark (Greenland) also provides for cooperative management of polar bears.

The Fish and Wildlife Service and the National Biological Service work together to monitor polar bears in Alaska, where they number about 5,000, and study their behavior. Cooperative efforts with Canada involve monitoring polar bears in the Beaufort Sea, and the agencies work with the Russian government to monitor the animals in the Chukchi Sea. The Fish and Wildlife Service also undertakes education and outreach efforts to inform the public about how polar bears can be protected from over- harvest.