Polar Bear: The Massive Animals
A giant white shape ambles across the Arctic tundra. When it finds a hole in the ice, it settles down at the edge and patiently waits. Suddenly, an unsuspecting seal pokes its head out of the hole to breathe. The great shape reaches out with a massive clawed paw and strikes the seal's head with a mighty blow. The seal is dragged out of the water and the polar bear begins its meal.
The polar bear is one of the most recognizable animals in the world. This large mammal belongs to the family Ursidae. Other members of this family include the grizzly bear of North America and the sun bear of Southeast Asia. Polar bears are found only in the northern polar regions of North America, Asia, and Europe.
Characteristics of Polar Bears
The polar bear is the largest member of the bear family. Males (boars) can weigh more than 1,700 pounds (765 kilograms). Females (sows) weigh about half as much.
Polar bears are perfectly adapted to their Arctic environment. They are covered by two layers of fur: a thick inner layer, or undercoat, and an outer layer of guard hairs. The undercoat helps keep the bear warm. The guard hairs are oily and shed water.
Despite appearances, the polar bear's fur is not white. Each individual hair is hollow and transparent. These features scatter the sunlight hitting the hair, making the hair look white. A polar bear's fur can also look yellow or brownish.
Beneath their fur polar bears have black skin. This helps the animals absorb heat from the sun. Beneath their skin, the bears have a thick layer of fat, which helps keep them warm and also helps them float when they swim in the water.
Polar bears have short thick legs and huge paws. The toes on their front feet are webbed, which helps them swim. Pads and fur on the bottom of their paws keep the bears from slipping on the ice. The bears' small ears minimize heat loss.
Because polar bears spend so much time in and around water, they are considered marine mammals like seals and whales.
The Lives of Polar Bears
Polar bears are primarily carnivores, which means they eat mostly meat. Their preferred food is ringed and bearded seals. But they will also eat birds, fish, foxes, walruses, bird eggs, and even some plants.
Polar bears are typically solitary animals. Adults come together only to mate, which happens in the spring. About eight months later, pregnant sows seek out a good place to dig a den. This is usually in a large snowbank. Inside the den, the temperature stays near the freezing point no matter how cold it is outside. In this safe warm shelter, a sow goes into a hibernation-like state and gives birth to as many as three cubs.
The cubs grow quickly on their mother's fatty milk. Their mother does not eat for the entire time she is in the den. She lives off the fat she stored up during the summer. After about four months, mother and cubs leave their den. Cubs stay with their mothers for about two years and then become independent.
Polar bears can live up to 20 years in the wild and up to 30 years in captivity.
Polar Bears and Their Environment
The polar bear is considered a vulnerable species by the International Union for Conservation of Nature (IUCN). The United States lists it as a threatened species under the Endangered Species Act. Native peoples hunt polar bears for their meat, fur, and fat. The bears are also hunted for sport.
The greatest threat to polar bears is climate change. Warmer temperatures in the Arctic have greatly reduced the region's amount of ice, which the bears rely on to hunt seals. When winters are shorter, the bears do not have enough time to feed and store up fat for the warm summer months.
During that time, they are stuck on land with few sources of food. With less food available, adult bears can become malnourished and die. Mothers may have fewer cubs, and the cubs that are born are less likely to survive. There is also a greater risk of bears coming into contact with people as the bears roam into settlements looking for food.