The largest of the land living carnivores, the polar bear, is one of the most powerful predators in the Arctic, observes Nutan Shukla
The nomadic polar bear

THE largest of the land-living carnivores, the polar bear, is one of the most powerful predators in the Arctic. Unlike its other relatives who are found in different parts of the world and are omnivorous, this massive predator is exclusively carnivorous and feeds predominantly on seals. Its semiaquatic lifestyle is a new adaptation for the bear family which helps him in finding food in the snowy deserts of the northern polar region. A layer of fat beneath the skin and thick fur keep it warm in its frozen world.

These beautiful, white creatures lead nomadic life, preferring to travel from one site to another where food is seasonally plentiful. They are expert seal killers and catch them while they are still in water. Bears seek out a breathing hole, which can be identified by the oily secretions on the surrounding ice, and sit there patiently. These holes are used by seals to come out of water to breath. As the head of the seal appears, quick as lightning, the bear’s enormous forepaw strikes out and hooks the seal up on to the ice, its skull crushed with one bludgeon-like blow to the head or its neck broken with one bite of the polar bear’s formidable jaws.

Seals and their pups hauled out on ice flows are stalked from across the ice and in the water. The bear uses ridges and dips to conceal its approach, slipping into the water for the final few yards. It paddles gently forward, resembling a chunk of floating ice.

One polar bear was once seen to stalk a seal and each time the victim turned, the bear would freeze and place its paw over its black nose to prevent the seal from spotting it. Ringed seals are the most common seals in the Arctic and so constitute the bulk of the polar bear diet, although bearded, hooded and harp seals are also sometimes taken.

The polar bear is unusual among European and American mammals in having virtually no ice age fossil record. Only a few scraps of bone, perhaps no more than 20,000 years old, are tentatively assigned to this species. The grizzly bear, whose fossil remains extend far back into ice age deposits, is the only likely direct ancestor of the polar bear.

At Wrangel Island in the east Siberia Sea, polar bears attack walruses and their pups. Over-enthusiastic bears jump on the backs of adults, but are dislodged by one shake of the walrus’ enormous bulk. The thick layer of blubber protects them from the polar bear’s teeth and claws. The bears are only successful if they can ambush a young walrus before it escapes to the sea.

In early spring bears seek out the breeding dens of ringed seals, which are found buried below the snow over sea ice. Using brute force the bear crashes through the roof of the den, surprising the seal family and grabbing the youngsters.

In the same kind of environment as that of polar bear, but at the other end of the world, prowls another master of ambush, the leopard seal. About ten feet long, with large, reptile-like heads and huge jaws studded with vicious teeth, leopard seals are solitary hunters. They attack just about anything that moves in the southern ocean, as long as it is smaller and more vulnerable, but their favourite food is penguin. The ambush often takes place at the edge of an ice shelf near a penguin colony, at places where penguins dive into the water to go fishing. If a leopard seal is about, penguins are agitated and are reluctant to leave the safety of the ice. Eventually, the weight of numbers forces the first birds to take the plunge, just what the seal has been waiting for.

The penguin is grabbed in the jaws, violently shaken and swallowed whole, minus the head and feet. Large birds, like emperor and king penguins, are dealt with in a different fashion; they are shaken until the skin splits and then ‘unwrapped’. A powerful flick of the seal’s head literally peels off the bird’s skin and feathers as far as the chin and legs, and the large breast muscles are consumed, leaving the rest.