Polar Bear (Ursus maritimus)

File:Polar Bear - Alaska.jpg

(http://en.wikipedia.org/wiki/File:Polar_Bear_-_Alaska.jpg)

  • Name: Polar Bear
  • Latin: Ursus maritimus
  • Classification: Mammal
  • Origin: Arctic Circle
  • Lifespan: 15-18 years

Taxonomy

  • Kingdom: Animalia (animals)
  • Phylum: Chordata (vertebrates)
  • Class: Mammalia (mammals)
  • Order: Carnivora (carnivores)
  • Family: Ursidae (Bears)
  • Genus: Ursus (Bears)
  • Species: Ursus maritimus (Polar bear)

Appearance

  • Length: Body-7.25-8ft (2.2-2.5m) Tail-3-5in (7.5-12.5cm)
  • Weight: 900-1,600lbs (410-720kg)

The neck of the polar bear is longer and the head is narrower than other species of bear which help the bear capture seals from their breathing holes in the sea ice. The paws are large and covered in fur which are used as paddles when swimming and as snow shoes on land. Polar bears have only four teats which is relative to their small litter size. Polar bears are the largest land carnivore alive in the world today with the males being larger and heavier than the females. The males weigh 880-1,750lbs (399-794kg) and the females weigh 440-660lbs (200-299kg).

Relatives

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  • Brown Bear (Ursus arctos) -LEAST CONCERN-
  • Giant Panda (Ailuropoda melanoluca) -ENDANGERED-
  • Sun Bear (Helarctos malayanus) -VULNERABLE-
  • Sloth Bear (Melursus ursinus) -VULNERABLE-

 Habitat & Distribution

The main habitat of polar bears is on offshore pack ice and along coasts. This allows them to remain in close contact with their main food source, seals. During the summer, when the polar region warms up, polar bears retreat to the land, then return when the sea ice reforms in the autumn.

Polar bear populations occupy the entire circumpolar Arctic region and over 40% of them live in Northern Canada. Other populations of polar bears can be found in Greenland, Denmark, Norway, Russian and the United States. These bears have also been reported as far north as the pole.

File:Polar bear range map.png

(http://en.wikipedia.org/wiki/File:Polar_bear_range_map.png)

Diet

Polar bears are the most carnivorous member of the bear family and require a diet based on large amounts of seal fat. The polar bear puts on most of its fat reserves between late April and mid-July to maintain its weight in the lean seasons which can last 3-4 months.

The majority of a polar bears diet is seals (largely ringed and bearded seals) which are an energy rich food source. A 121lb seal can provide 8 days of energy. When in abundance, the bears will only eat the fat and leave the carcass for scavengers such as foxes and ravens. Polar bears will feed on the carcasses of beluga whales, grey whales, walruses, narwhals and bowhead whales and can smell a carcass from 20 miles away.

When food is scarce, the polar bear will also eat musk ox, reindeer, small rodents, waterfowl, shellfish, fish, eggs, kelp, berries and human refuse. Occasionally, they will hunt beluga whales and adult walruses.

Behavior

Polar bears are crepuscular, being most active during dawn and dusk. The adult mothers with cubs will spend 19% of their time hunting in the spring and 38% in the summer, while adult male polar bears will spend 25% of their time hunting in the spring and 40% in the summer. When not hunting, these animals are often resting / sleeping. When lack of ice prevents seal hunting, they will spend as much as 87% of their time resting. Polar bears may make temporary snow or earthen pits to lie in.

Polar bears generally walk with a lumbering gait, which causes them to use twice as much energy to move at any given speed than most other mammals. These animals can however, run as fast as 40kph (25mph) for short distances.

Polar bears are mainly solitary with only two social units; adult females with cubs and breeding pairs. They will also often congregate to feed on whale carcasses and at dump sites.

Reproduction

Female polar bears reach sexual maturity at about 4-5 years while males will reach this stage at 6 years, although most won’t successfully mate until 8-10 years of age. Breeding occurs from March-June on the sea ice. The males and females will find each other by congregating at the best locations for seal hunting. The females breed about once every three years. The males will fight fiercely for the right to breed with the female, often to the death. Once paired, the male and female will stay together for about a week. Female polar bears are induced ovulators, meaning the act of mating will cause them to release an egg. Polar bears may have many different mates during their lifetime.

Once the egg is fertilised, the female will begin to put on weight. She will reach nearly twice her body weight and will then begin to build a den. The cubs will be born from Nov-Jan/ They are blind at birth, have fine fur and weight only two pounds. There are usually only two cubs per litter and will stay in the den for a couple of months. They will drink milk from the mothers body and she will survive on her stored fat.

The cubs will weight 22-33lbs when they are ready to leave the den for the first time. They will follow the mother onto the ice and she teaches them how to hunt for seals. The cubs become fully independent at 2-3 years old.

Adaptations

  • The fur of the polar bear is hollow. This serves two purposes. Firstly, it traps air and warms the animal from the cold. Secondly, it provides buoyancy and helps the polar bear to swim.
  • The polar bears liver can tolerate high levels of Vitamin A and as a result is never eaten by humans. The polar bears diet of ringed seals contains high levels of this vitamin.
  • The paws of the polar bear are large and fluffy. They serves a paddles when swimming and as snow shoes when walking on land.
  • The polar bears head is elongated which is useful when peering into seal breathing holes in the sea ice. They also have very large jaw muscles when help to haul seals from the water.

Threats

Climate change is the biggest threat to polar bears. As the temperatures in the Arctic get warmer, the sea ice melts. The polar bears rely on this sea ice for hunting seals and for meeting mates. These animals are also threatened by oil and gas development as well as potential oil spills. These spills directly harm the polar bears, deplete their prey and contaminate their habitat.

Polar bears are on the top of their food chain so have no natural predators however, they are hunted by people out of fear as well as for meat and hide.

Conservation

  • IUCN Status: Vulnerable

The polar bear was listed as a threatened species in the US under the Endangered Species Act in May 2008. The Polar Bears International is also the world’s leading polar bear conservation group. They are also protected by the International Agreement on Conservation of Polar Bears and their Habitat 1973. This legislation states that Canada, Greenland, Norway, the United States and the former Soviet Union (known as the five polar bear nations) shall protect polar bear habitat, ban hunting of bears from aircraft and large motorised boats, conduct and co-ordinate management and research efforts and exchange research results and data.

The United States Marine Mammal Protection Act 1972 aim to maintain the health and stability of the marine ecosystem and to obtain and maintain an optimum sustainable population of marine mammals. They are also listed under CITES appendix II. This states that all international trade of polar bears and their parts is permitted with proper documentation issued by the government of the exporting country.

Fun Facts

  • Male: Boar
  • Female: Sow
  • Young: Cub
  • Group: Sloth
  • Polar bears tend to overheat more than to be cold.
  • Polar bears have black skin under their white fur. This helps to absorb and trap heat and keep the animal warm.
  • They have been known to have tantrums. Experts have observed frustrated polar bears throwing chunks of ice, kicking piles of snow or growling in disappointment after losing prey they have been trying to catch.
  • Mothers will discipline their young with a whack to the head.
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