Published on February 11, 2013 by Amy
Polar bears are the largest land carnivore. Male polar bears or boars can weigh around 350 to 650 kg (772-1,433 lb.) and are about 2.5 to 3 m (8.2-9.8 ft.) long. Females or sows weigh about 150 to 250 kg (331-551 lb.) and are about 2 to 2.5 m (6.6-8.2 ft.) long. Both males and females have small tails that are about 7 to 12 cm (2.8-4.7 in.) long.
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Polar bear legs are large and stocky, and compared to other bears; polar bears have long bodies and slender necks. The head is long and relatively small with a long muzzle and a slightly arched snout, which ends in a broad, black nose. Polar bear’s have dark brown eyes that are set relatively close together, and have small rounded ears. The hind limbs are longer than the forelimbs, giving the polar bear their formidable stance.
Polar bears have large paws, which act like snowshoes, spreading out the bear’s weight as it moves over ice and snow. Each foot has five-toes, and each toe ends in a thick, curved, nonretractible claw. They use their claws for grasping prey and for traction when running or climbing on ice.
With thick, black pads on their feet that are covered with small, soft bumps, and long hairs growing between the pads and toes help to create friction between the foot and ice to prevent slipping.
A polar bear’s skin is black and has a dense and woolly coat that is 2.5 to 5 cm (1.2 in.) thick. The fur has an insulating layer of under hair, which is covered by a relatively thin layer of stiff, shiny, clear hairs. The hairs reflect light, giving the polar bear its white coloration. Oxidation from the sun, or staining, can make the hairs look yellow or brown.
The fur is oily and water repellent and does not mat when wet, allowing the polar bears to easily shake free of water and any ice that may form after swimming.
Polar bears completely shed and replace their fur annually, in May or June. The molt can last several weeks.
Polar bears have a layer of blubber up to 11 cm (4.3 in.) thick, which helps to keep them warm in the cold weather and while swimming. Since they are so well insulated they tend to overheat, in order to avoid this they move slowly and rest often.
Polar bears are strong swimmers. They can swim for several hours at a time over long distances and reach speeds of 10 kph (6.2 mph). Polar bears swim using the famous doggy-paddle style. The front paws are used to propel them and their hind feet and legs are used for steering. The average walking speed of a polar bear is 5.5 kph (3.4 mph) and they can run as fast as 40 kph (25 mph) but only for short distances.
Adult polar bears have no natural predators. But cubs are susceptible to other predators, such as wolves and as well as male polar bears. Polar bears can live 20 to 30 years, but only usually only live to be 15 to 18 years, due to such things as hunting, disease, starvation, and pollution. Another reason is that polar bears home ranges overlap with those of humans. These put both the bears and humans at risk.
It is estimated that there are between 21,000 and 28,000 polar bears left in the wild. In order to protect the polar bear, zoological parks have been established. These provide people the opportunity to learn about the polar bear. Also in order to better study the polar bear in the wild scientists use radio collars to track their movements.
Polar bears are distributed throughout the Arctic, and are mainly found in Greenland, Norway, Asia and North America. They inhabit Arctic sea ice, water, islands, and continental coastlines and prefer to be near landmasses around the edge of the polar basin.
Polar bears travel throughout the year within their own individual home ranges, which vary in size depending upon access to food, mates, and dens. They tend to be larger than other mammals around 50,000 to 350,000 square km. Polar bears don’t mark or defend their home ranges.
They have excellent sense of smell, which helps them to detect food. Polar bears are mainly carnivores, eating seals, walrus, whale, fish, small rodents, seabirds, and reindeer, as well as berries and various plants in the summer. Polar bears need an average of 2 kg (4.4 lb.) of fat per day to survive.
Polar bears use several methods when hunting. One common way of hunting for the polar bear is known as still-hunting. This is where the Polar bear remains motionless beside a breathing hole or lead edge waiting for a seal to surface. When a seal surfaces, the polar bear bites onto the head or upper body, then flips the entire seal onto the ice. Still-hunting usually takes less than one hour.
Another method is called stalking; this is most commonly used in the summer. The polar bear spots a seal and slowly stalks them. When the bear gets close enough it will charge the seal and kill it.
Also used in summer is the aquatic stalk, this is where the polar bear swims toward a landed seal. Once the polar bear reaches the ice edge, the bear quickly emerges from the water and grabs the seal with its claws or teeth.
Polar bears also stalk birth lairs of seals; mother bears with growing cubs most commonly use this method.
Polar bears are solitary animals. Basically only coming together to mate, share a large food source such as a dead whale or when a female has young. They are most active for the first part of the day and least active at the end of the day. They spend most of their time hunting, swimming, sleeping or resting. Polar bears don’t enter deep hibernation (that’s they go into a dormant or sleepy state during winter). Only pregnant female polar bears hibernate.
Polar bears use hissing, growling, champing of teeth, and soft chuffing when troubled and threatened. Cubs vocalize by using hissing, squalling, whimpering, lip smacking, and throaty rumblings. And mothers warn cubs with a chuffing or braying sound.
Mating occurs every two to three years during April and May. When a female is ready to mate she may have several male suitors. The males will fight fiercely until the strongest or largest male succeeds in chasing the others away. Once paired, the male and female stay together for a week or more. Gestation lasts eight to nine months. Pregnant females dig dens in the snow, where they will stay dormant until the birth of their young.
They give birth to anywhere from one to four cubs. The cubs are born weighing 454 to 680 g (16-24 oz.) and are about 30 cm (12 in.) long. Their eyes are closed and their fur is very fine at birth, making the cubs look hairless. The cubs stay with their mothers for about 1 to 2 years. Female polar bears reach sexual maturity at about 4 years, and males at about 6 years. However, most males don’t successfully mate until 8 to 10 years and older.