Polar bears: size, weight, paws, claws and teeth

Polar bears are the top predator in the arctic marine ecosystem and evolved from brown bears during the Pleistocene, the time period that spanned from 1.8 million to 11,000 years ago.

They have adapted to life in the north where temperatures do not exceed 10°C (50°F) in summer and typically fall to -30°C (-22°F) during winter. Their thick coat is made up of water repellent hairs that conserve heat. Under their dense fur is black skin, good for absorbing the rays of the arctic sun. A layer of fat up to 11 cm (4.3 in) thick keeps the bears warm, especially while swimming.

Polar bears are so well insulated that they have to move slowly to avoid overheating.

Adult males typically measure 200 to 250cm (6.5 to 8 feet) from the tip of the nose to the tip of the tail and weigh 400-600kg (880-1300 lbs). Females are about half this size.

These bears have enormous paws that function like snowshoes, distributing their weight to keep them from breaking through ice and snow. The pads of their feet are covered with soft, tiny growths called papillae, which increase friction between paw and ice and reduce the chance of slipping.

Polar bear claws are shorter, and more solid than their grizzly bear cousins, better suited for walking on ice or climbing steep banks.

They have sharp, jagged back teeth, and canines that are larger and sharper than grizzly teeth, but they swallow their food in large chunks rather than chewing.