Polar Bear

Polar Bear

Polar Bear in Alaska

Taxonomy

Kingdom: Animalia 

Phylum: Chordata 

Class: Mammalia 

Order: Carnivora 

Family: Ursidae 

Genus: Ursus 

Species: U. maritimus

Habitat

Polar bears are found throughout the circumpolar Arctic...

• along or near coasts

• on islands

• and most importantly, on sea ice.

The polar bear is often regarded as a marine mammal because it spends many months of the year at sea. However, it is the only living "marine mammal" with powerful, large limbs and feet that allow them to cover miles on foot and run on land. Its preferred habitat is the annual sea ice covering the waters over the continental shelf and the Arctic inter-island archipelagos. These areas, known as the "Arctic ring of life", have high biological productivity in comparison to the deep waters of the high Arctic. The polar bear tends to frequent areas where sea ice meets water, such as polynyas and leads (temporary stretches of open water in Arctic ice), to hunt the seals that make up most of its diet. Polar bears are therefore found primarily along the perimeter of the polar ice pack, rather than in the Polar Basin close to the North Pole where the density of seals is low.

Annual ice contains areas of water that appear and disappear throughout the year as the weather changes. Seals migrate in response to these changes, and polar bears must follow their prey. In Hudson Bay, James Bay, and some other areas, the ice melts completely each summer (an event often referred to as "ice-floe breakup"), forcing polar bears to go onto land and wait through the months until the next freeze-up. In the Chukchi and Beaufort seas, polar bears retreat each summer to the ice further north that remains frozen year-round.

Basic Anatomy

The polar bear is the largest living species of terrestrial predator.

Adult male polar bears weigh 350–700 kg (770–1,540 lb) and measure 2.4–3 metres (7 ft 10 in–9 ft 10 in) in total length. Around the Beaufort Sea, however, mature males reportedly average 450 kg (1,000 lb). Adult females are roughly half the size of males and normally weigh 150–250 kg (330–550 lb), measuring 1.8–2.4 metres (5 ft 11 in–7 ft 10 in) in length. Elsewhere, a slightly larger estimated average weight of 260 kg (570 lb) was claimed for adult females. When pregnant, however, females can weigh as much as 500 kg (1,100 lb). The polar bear is among the most sexually dimorphic of mammals, surpassed only by the pinnipeds such as elephant seals. The largest polar bear on record, reportedly weighing 1,002 kg (2,209 lb), was a male shot at Kotzebue Sound in northwestern Alaska in 1960. This specimen, when mounted, stood 3.39 m (11 ft 1 in) tall on its hindlegs. The shoulder height of an adult polar bear is 122 to 160 cm (4 ft 0 in to 5 ft 3 in). While all bears are short-tailed, the polar bear's tail is relatively the shortest amongst living bears, ranging from 7 to 13 cm (2.8 to 5.1 in) in length.

The 42 teeth of a polar bear reflect its highly carnivorous diet. The cheek teeth are smaller and more jagged than in the brown bear, and the canines are larger and sharper.

Polar bears are superbly insulated by up to 10 cm (4 in) of blubber, their hide and their fur; they overheat at temperatures above 10 °C (50 °F), and are nearly invisible under infrared photography. Polar bear fur consists of a layer of dense underfur and an outer layer of guard hairs, which appear white to tan but are actually transparent. The guard hair is 5–15 cm (2–6 in) over most of the body. Polar bears gradually moult from May to August, but, unlike other Arctic mammals, they do not shed their coat for a darker shade to camouflage themselves in the summer conditions. The hollow guard hairs of a polar bear coat were once thought to act as fiber-optic tubes to conduct light to its black skin, where it could be absorbed; however, this theory was disproven by recent studies.

The white coat usually yellows with age. When kept in captivity in warm, humid conditions, the fur may turn a pale shade of green due to algae growing inside the guard hairs. Males have significantly longer hairs on their forelegs, which increase in length until the bear reaches 14 years of age. The male's ornamental foreleg hair is thought to attract females, serving a similar function to the lion's mane. The polar bear has an extremely well developed sense of smell, being able to detect seals nearly 1.6 km (1 mi) away and buried under 1 m (3 ft) of snow. Its hearing is about as acute as that of a human, and its vision is also good at long distances.

The polar bear is an excellent swimmer and individuals have been seen in open Arctic waters as far as 300 km (200 mi) from land. With its body fat providing buoyancy, it swims in a dog paddle fashion using its large forepaws for propulsion. Polar bears can swim 10 km/h (6 mph). When walking, the polar bear tends to have a lumbering gait and maintains an average speed of around 5.6 km/h (3.5 mph). When sprinting, they can reach up to 40 km/h (25 mph).

Importances to Environment 

Besides the fact that theyare cute and cuddly - polar bears are important for many reasons.  Polar bears are what are known as an umbrella species; many organisms are connected to polar bears via a food web.  For example, the Arctic Fox depends on the polar bear for food - they eat the left over seal carcass after the polar bear is done.  Polar bears feed on seals, without the predator then the seal population might increase also affecting the fish that seals feed on - and so on.

Another reason to care about the polar bears is the overall notion of biodiversity.  Biodiversity refers to the number of different species.  For example there are millions of different species of beetles.  While it may not seem important to have so many types, each is a specialist in terms of food, habitat, behavior, etc.  Each plays a role in ecosystems.  A great analogy for this is an engine.  If you pull one part out of an engine, but don't know what it is - you wouldn't just throw it away. You'd save it because maybe later you would understand it's importance and use.

Another reason there is so much focus on polar bears is because they get attention of the public.  They serve as a sort of "ambassador" species for what's happening in the Arctic right now.  They serve as a gauge to measure affects of climate change.

Benefits for Human 

They provide good sources of foods, however their livers are poisonous, but their livers have high amount of vitamins. Their furs can be used for making great waterproof shoes, coats, etc. 

Photo & Video Gallery of Polar Bears