How are polar bears important to earth, humans, and the enviroment?

Since an attack on a walrus tends to be an extremely protracted and exhausting venture, bears have been known to abandon the hunt after making the initial injury. 60 Polar bears have also been seen to prey on beluga whales, by swiping at them at breathing holes. The whales are of similar size to the walrus and nearly as difficult for the bear to subdue.

Polar bears very seldom attack full-grown adult whales. Most terrestrial animals in the Arctic can outrun the polar bear on land as polar bears overheat quickly, and most marine animals the bear encounters can outswim it. In some areas, the polar bear's diet is supplemented by walrus calves and by the carcasses of dead adult walruses or whales, whose blubber is readily devoured even when rotten.

With the exception of pregnant females, polar bears are active year-round,62 although they have a vestigial hibernation induction trigger in their blood. Unlike brown and black bears, polar bears are capable of fasting for up to several months during late summer and early fall, when they cannot hunt for seals because the sea is unfrozen. 62 When sea ice is unavailable during summer and early autumn, some populations live off fat reserves for months at a time.

45 Polar bears have also been observed to eat a wide variety of other wild foods, including muskox, reindeer, birds, eggs, rodents, shellfish, crabs, and other polar bears. They may also eat plants, including berries, roots, and kelp, however none of these are a significant part of their diet. 59 The polar bear's biology is specialized to require large amounts of fat from marine mammals, and it cannot derive sufficient caloric intake from terrestrial food.

Being both curious animals and scavengers,5965 polar bears investigate and consume garbage where they come into contact with humans. 59 Polar bears may attempt to consume almost anything they can find, including hazardous substances such as styrofoam, plastic, car batteries, ethylene glycol, hydraulic fluid, and motor oil. 5965 The dump in Churchill, Manitoba was closed in 2006 to protect bears, and waste is now recycled or transported to Thompson, Manitoba.

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. 68 Satiated polar bears rarely attack humans unless severely provoked, whereas hungry polar bears are extremely unpredictable and are known to kill and sometimes eat humans.

61 Polar bears are stealth hunters, and the victim is often unaware of the bear's presence until the attack is underway. 69 Whereas brown bears often maul a person and then leave, polar bear attacks are more likely to be predatory and are almost always fatal. 69 However, due to the very small human population around the Arctic, such attacks are rare.

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,61 and polar bear zoologist Nikita Ovsianikov has described adult males as having "well-developed friendships."68 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.

70 Polar bears have a wide range of vocalisations, including bellows, roars, growls, chuffs and purrs. 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. 7273 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.

72 This kind of social interaction is uncommon; it is far more typical for polar bears to behave aggressively towards dogs. Courtship and mating take place on the sea ice in April and May, when polar bears congregate in the best seal hunting areas. 74 A male may follow the tracks of a breeding female for 100 km (60 mi) or more, and after finding her engage in intense fighting with other males over mating rights, fights which often result in scars and broken teeth.

74 Polar bears have a generally polygynous mating system; recent genetic testing of mothers and cubs, however, has uncovered cases of litters in which cubs have different fathers. 75 Partners stay together and mate repeatedly for an entire week; the mating ritual induces ovulation in the female. After mating, the fertilized egg remains in a suspended state until August or September.