Fun Facts of Polar Bears
Most of the Arctic Ocean's surface is frozen for most of the year, but it partially melts and breaks in the summer to form bands of relatively open water along some coastlines. When the ice in the southern part of the Arctic Ocean melts, most of the polar bears move north to stay on the ice, but some move south and spend the summer on the tundra. Most of these bears migrate to the same areas each summer and winter year after year in search of food. Ringed seals are their main source of food, but they occasionally also eat bearded seals, walruses, fish, mussels, and berries. Some have even found garbage dumps easy hunting. During the spring, when seals are easy to find, the bears eat so many seals that they get quite fat, some gaining more than 200 pounds. This fat is used up during the winter when the seals are more difficult to find.
Seals are very fast in the water, but polar bears are unusually clever at solving problems in order to obtain food. Since these bears have an extraordinary sense of smell, they can smell the seals even through thick layers of ice. Polar bears observe and learn that seals come out of holes in the ice. If they smell a seal beneath the ice, then they will commonly sit and wait by a hole in the ice for a seal to come out. A polar bear may patiently wait for hours by the hole. When the seal appears the bear, with lightning speed, slaps the seal with its giant paw and pulls the seal out through the hole.
When a bear spots a seal on the ice, it will try to sneak up on it. The bear is careful to stay downwind, which means the wind blows from the seal toward the bear so the seal does not smell the bear. The white color of the polar bear's fur allows the bear to be camouflaged in the snow and ice, so it can better stalk its prey. Since it is not easily seen when it lays flat on the ice on its belly, the bear can slowly creep toward a seal and grab the seal before it can escape into the water. To catch a seal lying near the water's edge, a bear will swim quietly toward the seal, then dive under the water so it can spring to the surface and lunge at the unsuspecting seal.
Polar bears are the only marine bears. They are expert swimmers and have been known to swim as far as 50 miles (80 km). In comparison to other bears, their bodies are longer and more streamlined (shape offering the least resistance to motion through fluids, which are gasses or liquids). Polar bears are large, strong, and very fierce. Their very broad front feet help them swim. They paddle with their front legs and steer with their rear legs. The thick layer of fat under the bear's skin called blubber helps it to stay warm in the icy Arctic water.
All polar bears look white, but each hair is actually a transparent tube. Some of the light hitting the transparent hair is scattered, in the same way that light hitting the water in clouds is scattered, causing the hair and clouds to look white. Some light hitting the hair passes through the tubes, where it is absorbed by the bear's skin, which warms the bear. The skin of polar bears is actually black, but the fur is so thick that it totally covers the black skin.
Polar bear fur is made up of long hairs separated by short hairs. The long hairs keep the skin dry and warm. The short hairs create spaces where air is trapped. Trapped air is a good insulator, so it helps to warm the bear. To warm up, the bear can fluff up his fur, which traps more air. To cool off, the bear can slick his fur down, which pushes out air. The fur becomes thicker in the winter, and some is shed in the spring in preparation for the warmer summer season.
Polar bears are the largest land predator. The largest polar bear ever measured was a male that stood more than 11 feet (3.3 m) tall when standing on its hind legs and weighed 2,210 pounds (1,005 kg). The average range for head and body length is 6 to 8 feet (1.8 to 2.4 m). Most male polar bears weigh an average of about 880 pounds (350 kg), and most females weigh about 550 pounds (250 kg). Almost everything about a polar bear is big, except its ears, which are tiny to prevent heat loss from the body.