Scientific name: Ursus maritimus
Conservation status: Vulnerable

Appearance

Polar BearPolar bears have a more elongated body shape than the brown bear and have a longer skull and nose. They have stocky legs and a small tail and ears. They do have very large feet though which help them when walking on the snow and ice and also act like big paddles when they are swimming. The pads of the feet are covered with small bumps which help give them extra grip on the ice. They also have short strong claws which help them to grip prey and also help with digging in the ice. The feet of an adult polar bear can measure 30 cm (12 in) across. Polar bears have 42 teeth due to the fact that they have a carnivorous diet.

The polar bear is covered in a thick undercoat of fur protected by an outer coat of long guard hairs. These guard hairs stick together when they are wet and give the polar bear a waterproof barrier to help keep them dry. It appears as though polar bears have white fur but that is not the case, the hair is actually transparent hollow tubes filled with air. The skin of the polar bear underneath the fur is actually black which helps them to soak up the sun. Polar bears are insulated by a layer of blubber that is between 5 to 10 cms thick (2 to 4 in) that helps them stay warm in the cold water or freezing air. The polar bear can also use it to survive on if they are not able to find food for awhile.

The length of the average polar bear is 2 to 3 metres (6.6 to 10 ft) with the average weight for a male 300 to 800 kilograms (660 to 1760 pounds) and female 150 to 300 kilograms (330 to 660 pounds). The female is roughly half the size of the male polar bear.

Lifespan

The lifespan of the polar bear is about 18 years for wild males, mid twenties for wild females and around mid thirties for polar bears in zoos.

Diet

The main part of the polar bears diet is the ringed and bearded seal. They prey on the seal when they come up from holes in the ice to breathe or come out to rest. The polar bear has an extremely developed sense of smell and will wait by the hole and be able to smell when the seals breath is close to the surface, they will reach into the hole and drag the seal out. The polar bear bites the seal on the head to crush its skull to kill it. They will sometimes hunt a seal on the ice by crouching quietly behind it and then rushing forward to pounce on the seal. Another way that they can get seals is to raid the birth areas that seals have created in the snow. Adult polar bears will eat the skin and blubber of the seal first and then eat the rest of it. They will also eat walruses, beached whales, grass and seaweed. They sometimes also eat plants and berries etc but these are not the main parts of their diet.

Habitat

Polar bears are found in Denmark (Greenland), Norway, Russia, Alaska and Canada. Their preferred habitat is artic, tundra and woodlands. They like to stay on the sea ice packs all year round if they can because this keeps them in close contact with their main food source the seal. When the summer comes and the ice packs start to melt the polar bears will travel miles to stay on the ice. If the polar bears are forced to remain on land for a while because the ice has melted then they will live on their fat reserves until the ice forms again.

Reproduction

Polar bears mate between April and May. Once the polar bear has mated the female is able to keep the fertilized egg in a suspended state until about August and September. This allows her to be able to eat a lot of food to build up her fat deposits to live on while she is in the maternity den or until conditions are right. Once the female becomes pregnant she will make a maternity den in the snow with a narrow entrance tunnel leading to one to three chambers. In the den the female will enter a state that is similar to hibernation, however it does not involve continuous sleeping she will just slow her heart rate down. The gestation period for polar bears varies depending on when the female actually becomes pregnant after mating. The female will give birth to 1-3 cubs with 2 being typical. The cubs are born blind and helpless and are covered with light downy fur and weigh around .6 kgs (1.3 pounds). The cubs will stay with the mother in the den for the next 3-4 months drinking their mothers milk which is very rich in fat. The mother will then break open the entrance to the den and the cubs will weigh about 10-15 kgs (22 to 33 lbs). They will stay with the mother close to the den for awhile to let the cubs get used to walking on the ice etc, then they will walk to the ice packs so the mother can again start catching seals. The mother will nurse and protect her cubs for about two and a half years, after which they can go on their own and will become sexually mature at about the age of 5.

Behaviour

Polar bear adults usually live solitary lives but they can sometimes be seen playing together. Young male polar bears especially like to play fight and this might be used as practice for when they may have to fight during the mating season.
Polar bears communicate using a wide variety of sounds including purrs, roars, bellows and growls.
Polar bears can be dangerous to humans especially if they are hungry but if they are able to get food they will usually only attack humans if they are provoked however they are extremely unpredictable.
When the temperature gets really cold they may make a den in the snow and sleep. They do not hibernate as other bears do but they are able to slow down their bodily functions such as their heart beat. This allows them to conserve their energy and live of their fat deposits until they are able to hunt again.

Quick facts

Polar bears spend most a lot of time in the water.

They have an extremely powerful sense of smell, and can smell a seal on the ice about 32 kms (20 miles) away and can smell a seals den that has been covered with snow.

Polar bears can see really well under the water, and can see a meal about 4.6 metres (15 ft) away.

It is believed that polar bears go through a moulting period where they will lose some of their fur, but this happens not to replace their whole coat but to regulate their body temperature when the weather starts to get warmer.

Sources

http://en.wikipedia.org/wiki/Polar_bear

http://www.sandiegozoo.org/animalbytes/t-polar_bear.html