Approximate worldwide winter
distribution of polar bears (light gray).
Polar bears are distributed throughout most
ice-covered seas of the Northern Hemisphere.
The polar bear or the sea/ice bear are the world's largest land predators. They can be found in the Artic, the U.S. (Alaska), Canada, Russia, Denmark (Greenland), and Norway. Each of these countries either banned hunting or established rules for how many polar bears could be hunted within its own boundaries. These rules help keep polar bear populations stable. Today, 25,000 to 40,000 polar bears roam the Arctic.
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Around the age of four or five the female polar bear can start having babies. They usually only have two cubs and they have these babies in a cave they've dug in a large snow drift. They stay there over winter and come out in spring with the babies.
The babies are much smaller than human babies when they're born. They are the size of a rat and weigh little more than a pound. They can grow to full man size in a year if they have lots of food.
Pair of polar bear cubs.
photo by: US Fish and Wildlife
Male polar bears may grow 10 feet tall and weigh over 1400 pounds. Females reach seven feet and weigh 650 pounds. In the wild polar bears live up to age 25.
Despite what we think, a polar bear's fur is not white. Each hair is a clear hollow tube. Polar bears look white because each hollow hair reflects the light. On sunny days, it traps the sun's infrared heat and keeps the bear warm at 98 degrees F (when they're resting).
Polar bear fur is oily and water repellent. The hairs don't mat when wet, allowing the polar bears to easily shake free of water and any ice that may form after swimming.
Underneath the fur, a polar bear's skin is actually black -- the black skin soaks up the sun's heat and helps them stay warm.
Polar bears also have a 4 inch layer of fat underneath their skin. This prevents them from losing any of their heat. In fact, if you look at a polar bear with an infared camera, they are pretty close to invisible (in other words, they don't give off any heat!)
The smallest foot pad is the front track
and the larger is the hind track.
Polar bears have wide front paws with slightly webbed toes that help them swim. They paddle with their front feet and steer with their hind feet. Paw pads with rough surfaces help prevent polar bears from slipping up on the ice.
Polar bears have been known to swim 100 miles (161 kilometers) at a stretch.
Polar bears primarily eat seals. They often rest silently at a seal’s breathing hole in the ice, waiting for a seal in the water to surface. Once the seal comes up, the bear will spring and sink its jagged teeth into the seal’s head.
They have a special liver that allows them to process all of the seal fat they eat - seals store a lot of vitamin A in their blubber which allows them to survive and grow quickly. A polar bear's liver contains 10 times more vitamin A than any other animal on earth - their liver has evolved to allow them to process and eat all of the seal blubber they need to stay alive.
Sometimes the polar bear stalks its prey. It may see a seal lying near its breathing hole and slowly move toward it, then charge it, biting its head or grabbing it with its massive claws. A polar bear may also hunt by swimming beneath the ice.
Humans are the polar bears only predator. Baby polar bears often starve. In fact, 70 percent do not live to their third birthday. Sometimes seals are hard to find, especially in the summer when the ice has melted. All across the Arctic, man is moving in to mine oil and coal and there is less space for the polar bear to live. Oil spills can be very dangerous. A bear with oil on its coat cannot regulate its body temperature properly. If the bear eats the oil while grooming it could die.
Man made pollution is also a cause of death. At each stage of the food chain, pollutants get more concentrated. By the end when the polar bear eats the seal and it could be lethal.
Polar Bears are considered marine mammals -- just like seals, whales and dolphins. Although polar bears are related to the brown bear, they have evolved over time to live in cold northern arctic climates. Their population is on the decline and they are considered a "vulnerable" species.
photo by: US Fish and Wildlife
Protecting polar bears isn't just a matter of being nice. Their body is very different than most mammals -- they are able to process large amounts of fat (seal blubber) and are able to lose and gain large amounts of weight through the year without causing stress health problems. Scientists are studying them to see if they can provide a key to human diseases like diabetes and heart disease!