Hunting and diet
The long muzzle and neck of the polar bear help it to search in deep holes for seals, while powerful hindquarters enable it to drag massive prey.[62]
The polar bear is the most carnivorous member of the bear family, and throughout most of its range, its diet primarily consists of ringed (Pusa hispida) and bearded seals (Erignathus barbatus).[63] The Arctic is home to millions of seals, which become prey when they surface in holes in the ice in order to breathe, or when they haul out on the ice to rest.[62][64] Polar bears hunt primarily at the interface between ice, water, and air; they only rarely catch seals on land or in open water.[65]
The polar bear's most common hunting method is called still-hunting:[66] The bear uses its excellent sense of smell to locate a seal breathing hole, and crouches nearby in silence for a seal to appear. The bear may lay in wait for several hours. When the seal exhales, the bear smells its breath, reaches into the hole with a forepaw, and drags it out onto the ice. The polar bear kills the seal by biting its head to crush its skull. The polar bear also hunts by stalking seals resting on the ice: Upon spotting a seal, it walks to within 90 m (100 yd), and then crouches. If the seal does not notice, the bear creeps to within 9 to 12 m (30 to 40 ft) of the seal and then suddenly rushes forth to attack.[62] A third hunting method is to raid the birth lairs that female seals create in the snow.[66]
A widespread legend tells that polar bears cover their black noses with their paws when hunting. This behavior, if it happens, is rare – although the story exists in native oral history and in accounts by early Arctic explorers, there is no record of an eyewitness account of the behavior in recent decades.[60]
Polar bear at a whale carcass
Mature bears tend to eat only the calorie-rich skin and blubber of the seal, which are highly digestible,[67] whereas younger bears consume the protein-rich red meat.[62] Studies have also photographed polar bears scaling near-vertical cliffs, to eat birds' chicks and eggs.[68][69][70] For subadult bears which are independent of their mother but have not yet gained enough experience and body size to successfully hunt seals, scavenging the carcasses from other bears' kills is an important source of nutrition. Subadults may also be forced to accept a half-eaten carcass if they kill a seal but cannot defend it from larger polar bears. After feeding, polar bears wash themselves with water or snow.[60]
The polar bear is perhaps unequaled by any other living land predator in its enormous physical power. However, its primary prey species, the ringed seal, is much smaller than itself, and many of the seals hunted are pups rather than adults. Ringed seals are born weighing 5.4 kg (12 lb) and grown to an estimated average weight of only 60 kg (130 lb).[71][72] They also in places prey heavily upon the harp seal (Pusa groenlandica) or the harbor seal.[73] The bearded seal, on the other hand, can be nearly the same size as the bear itself, averaging 270 kg (600 lb).[72] Adult male bearded seals, at 350 to 500 kg (770 to 1,100 lb) are believed to be too large for a female bear to overtake,[74] and so are potential prey only for mature male bears.[75] Enormously powerful large males also occasionally attempt to hunt and kill even larger prey items.[76] It can kill an adult walrus (Odobenus rosmarus),[73][77] although this is rarely attempted. At up to 2,000 kg (4,400 lb) and a typical adult mass range of 600 to 1,500 kg (1,300 to 3,300 lb), a walrus can be more than twice the bear's weight,[78] and has up to 1-metre (3 ft)-long ivory tusks that can be used as formidable weapons. Most attacks on walruses occur when the bear charges a group and either targets the slower moving walruses, usually either young or infirm ones, or a walrus that is injured in the rush of walruses trying to escape.[citation needed] They will also attack even adult walruses when their diving holes have frozen over or intercept them before they can get back to the diving hole in the ice. Yet, polar bears very seldom attack full-grown adult walruses, with the largest male walrus probably invulnerable unless otherwise injured or incapacitated. Since an attack on a walrus tends to be an extremely protracted and exhausting venture, bears have been known to back down from the attack after making the initial injury to the walrus.[79] Polar bears have also been seen to prey on beluga whales (Delphinapterus leucas)[73] and narwhals (Monodon monoceros),[73] 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.[80][81] 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.[82] Polar bears sometimes like to go fishing where they swim underwater to catch fish like the arctic charr or the Fourhorn sculpin.[64]
Some characteristic postures:
1. – at rest;
2. – at an estimated reaction;
3. – when feeding
With the exception of pregnant females, polar bears are active year-round,[83] 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.[83] When sea ice is unavailable during summer and early autumn, some populations live off fat reserves for months at a time.[51] Being both curious animals and scavengers,[78][84] polar bears investigate and consume garbage where they come into contact with humans.[73][78] 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.[78][84] The dump in Churchill, Manitoba was closed in 2006 to protect bears, and waste is now recycled or transported to Thompson, Manitoba.[85][86]
Hunting and diet
The long muzzle and neck of the polar bear help it to search in deep holes for seals, while powerful hindquarters enable it to drag massive prey.[62]
The polar bear is the most carnivorous member of the bear family, and throughout most of its range, its diet primarily consists of ringed (Pusa hispida) and bearded seals (Erignathus barbatus).[63] The Arctic is home to millions of seals, which become prey when they surface in holes in the ice in order to breathe, or when they haul out on the ice to rest.[62][64] Polar bears hunt primarily at the interface between ice, water, and air; they only rarely catch seals on land or in open water.[65]
The polar bear's most common hunting method is called still-hunting:[66] The bear uses its excellent sense of smell to locate a seal breathing hole, and crouches nearby in silence for a seal to appear. The bear may lay in wait for several hours. When the seal exhales, the bear smells its breath, reaches into the hole with a forepaw, and drags it out onto the ice. The polar bear kills the seal by biting its head to crush its skull. The polar bear also hunts by stalking seals resting on the ice: Upon spotting a seal, it walks to within 90 m (100 yd), and then crouches. If the seal does not notice, the bear creeps to within 9 to 12 m (30 to 40 ft) of the seal and then suddenly rushes forth to attack.[62] A third hunting method is to raid the birth lairs that female seals create in the snow.[66]
A widespread legend tells that polar bears cover their black noses with their paws when hunting. This behavior, if it happens, is rare – although the story exists in native oral history and in accounts by early Arctic explorers, there is no record of an eyewitness account of the behavior in recent decades.[60]
Polar bear at a whale carcass
Mature bears tend to eat only the calorie-rich skin and blubber of the seal, which are highly digestible,[67] whereas younger bears consume the protein-rich red meat.[62] Studies have also photographed polar bears scaling near-vertical cliffs, to eat birds' chicks and eggs.[68][69][70] For subadult bears which are independent of their mother but have not yet gained enough experience and body size to successfully hunt seals, scavenging the carcasses from other bears' kills is an important source of nutrition. Subadults may also be forced to accept a half-eaten carcass if they kill a seal but cannot defend it from larger polar bears. After feeding, polar bears wash themselves with water or snow.[60]
The polar bear is perhaps unequaled by any other living land predator in its enormous physical power. However, its primary prey species, the ringed seal, is much smaller than itself, and many of the seals hunted are pups rather than adults. Ringed seals are born weighing 5.4 kg (12 lb) and grown to an estimated average weight of only 60 kg (130 lb).[71][72] They also in places prey heavily upon the harp seal (Pusa groenlandica) or the harbor seal.[73] The bearded seal, on the other hand, can be nearly the same size as the bear itself, averaging 270 kg (600 lb).[72] Adult male bearded seals, at 350 to 500 kg (770 to 1,100 lb) are believed to be too large for a female bear to overtake,[74] and so are potential prey only for mature male bears.[75] Enormously powerful large males also occasionally attempt to hunt and kill even larger prey items.[76] It can kill an adult walrus (Odobenus rosmarus),[73][77] although this is rarely attempted. At up to 2,000 kg (4,400 lb) and a typical adult mass range of 600 to 1,500 kg (1,300 to 3,300 lb), a walrus can be more than twice the bear's weight,[78] and has up to 1-metre (3 ft)-long ivory tusks that can be used as formidable weapons. Most attacks on walruses occur when the bear charges a group and either targets the slower moving walruses, usually either young or infirm ones, or a walrus that is injured in the rush of walruses trying to escape.[citation needed] They will also attack even adult walruses when their diving holes have frozen over or intercept them before they can get back to the diving hole in the ice. Yet, polar bears very seldom attack full-grown adult walruses, with the largest male walrus probably invulnerable unless otherwise injured or incapacitated. Since an attack on a walrus tends to be an extremely protracted and exhausting venture, bears have been known to back down from the attack after making the initial injury to the walrus.[79] Polar bears have also been seen to prey on beluga whales (Delphinapterus leucas)[73] and narwhals (Monodon monoceros),[73] 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.[80][81] 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.[82] Polar bears sometimes like to go fishing where they swim underwater to catch fish like the arctic charr or the Fourhorn sculpin.[64]
Some characteristic postures:
1. – at rest;
2. – at an estimated reaction;
3. – when feeding
With the exception of pregnant females, polar bears are active year-round,[83] 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.[83] When sea ice is unavailable during summer and early autumn, some populations live off fat reserves for months at a time.[51] Being both curious animals and scavengers,[78][84] polar bears investigate and consume garbage where they come into contact with humans.[73][78] 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.[78][84] The dump in Churchill, Manitoba was closed in 2006 to protect bears, and waste is now recycled or transported to Thompson, Manitoba.[85][86]
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