The polar bear (Ursus maritimus) is a bear native to the Arctic Ocean and its surrounding seas. The world's largest predator found on land, an adult male weighs around 400–680 kg (880–1,500 lb),[3] while an adult female is about half that size. Although it is closely related to the brown bear, it has evolved to occupy a narrow ecological niche, with many body characteristics adapted for cold temperatures, for moving across snow, ice, and open water, and for hunting the seals which make up most of its diet.[4] As it can hunt consistently only from sea ice, the polar bear spends much of the year on the frozen sea, although most polar bears are born on land.
Naming and etymology
Constantine John Phipps was the first to describe the polar bear as a distinct species. He chose the scientific name Ursus maritimus, the Latin for 'maritime bear', due to the animal's native habitat. The Inuit refer to the animal as nanook[8], (transliterated as nanuuq in the Inupiat language[9], nanuuk in Siberian Yupik, and also as nanuq or nanuk[citation needed]; and hence the title of the early 20th century documentary on Inuit life, Nanook of the North). The bear is umka in the Chukchi language. In Russian, it is usually called Белый Медведь (Bely Medved, the White Bear), though an older word still in use is Ошкуй (Oshkuy, which comes from the Komi Oski, "bear").In Quebec French, the polar bear is referred to as Ours polaire.
Habitat
The polar bear is often regarded as a marine mammal because it spends many months of the year at sea.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 relatively 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.[26] 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.
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.
Behavior
Unlike grizzly bears, polar bears are not territorial. Although stereotyped as being voraciously aggressive, they are normally cautious in confrontations, and often choose to escape rather than fight.Fat polar bears rarely attack humans unless severely provoked, whereas hungry polar bears are extremely unpredictable and are known to kill and sometimes eat humans.Polar bears are stealth hunters, and the victim is often unaware of the bear's presence until the attack is underway. Whereas brown bears often maul a person and then leave, polar bear attacks are almost always fatal.
In general, adult polar bears live solitary lives. Yet, they have often been seen playing together for hours at a time and even sleeping in an embrace, and polar bear zoologist Nikita Ovsianikov has described adult males as having "well-developed friendships." Cubs are especially playful as well. Among young males in particular, play-fighting may be a means of practicing for serious competition during mating seasons later in life.
In 1992, a photographer near Churchill took a now widely-circulated set of photographs of a polar bear playing with a Canadian Eskimo Dog a tenth of its size. The pair wrestled harmlessly together each afternoon for ten days in a row for no apparent reason, although the bear may have been trying to demonstrate its friendliness in the hope of sharing the kennel's food.This kind of social interaction is uncommon; it is far more typical for polar bears to behave aggressively towards dogs.
In general, adult polar bears live solitary lives. Yet, they have often been seen playing together for hours at a time and even sleeping in an embrace, and polar bear zoologist Nikita Ovsianikov has described adult males as having "well-developed friendships." Cubs are especially playful as well. Among young males in particular, play-fighting may be a means of practicing for serious competition during mating seasons later in life.
In 1992, a photographer near Churchill took a now widely-circulated set of photographs of a polar bear playing with a Canadian Eskimo Dog a tenth of its size. The pair wrestled harmlessly together each afternoon for ten days in a row for no apparent reason, although the bear may have been trying to demonstrate its friendliness in the hope of sharing the kennel's food.This kind of social interaction is uncommon; it is far more typical for polar bears to behave aggressively towards dogs.
Global warming
The IUCN, Arctic Climate Impact Assessment, United States Geological Survey and many leading polar bear biologists have expressed grave concerns about the impact of global warming, including the belief that the current warming trend imperils the survival of the species.
The key danger posed by global warming is malnutrition or starvation due to habitat loss. Polar bears hunt seals from a platform of sea ice. Rising temperatures cause the sea ice to melt earlier in the year, driving the bears to shore before they have built sufficient fat reserves to survive the period of scarce food in the late summer and early fall.Reduction in sea-ice cover also forces bears to swim longer distances, which further depletes their energy stores and occasionally leads to drowning.Thinner sea ice tends to deform more easily, which appears to make it more difficult for polar bears to access seals.Insufficient nourishment leads to lower reproductive rates in adult females and lower survival rates in cubs and juvenile bears, in addition to poorer body condition in bears of all ages.
In addition to creating nutritional stress, a warming climate is expected to affect various other aspects of polar bear life: Changes in sea ice affect the ability of pregnant females to build suitable maternity dens. As the distance increases between the pack ice and the coast, females must swim longer distances to reach favored denning areas on land. Thawing of permafrost would affect the bears who traditionally den underground, and warm winters could result in den roofs collapsing or having reduced insulative value. For the polar bears that currently den on multi-year ice, increased ice mobility may result in longer distances for mothers and young cubs to walk when they return to seal-hunting areas in the spring.Disease-causing bacteria and parasites would flourish more readily in a warmer climate.
Problematic interactions between polar bears and humans, such as foraging by bears in garbage dumps, have historically been more prevalent in years when ice-floe breakup occurred early and local polar bears were relatively thin.Increased human-bear interactions, including fatal attacks on humans, are likely to increase as the sea ice shrinks and hungry bears try to find food on land.
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