Polar bears

28 February 2010 | Fact sheet

How big are polar bears and how long do they live? How do they adapt to the Arctic environment and why are there no polar bears in Antarctica?

1. How big do polar bears get?

Polar bears are the largest living carnivorous quadruped (animals with four legs).

Adult males measure 240-260cm and usually weigh 400-600kg, although they can weigh up to 800kg and maybe even more. They do not reach maximum size until they are 8-14 years old. Adult females are about half the size of males and reach adult size at an age of 5-6 years, when most of them weigh 150-250kg.

2. How are polar bears adapted to the cold environment of the Arctic, often with little food availability?

Polar bears are marvellously adapted to their Arctic surroundings. Their glossy 'guard' hairs and dense under-fur, the thick layer of fat beneath their skin, and their size protect them against the cold. The guard hairs shed water easily, so that after a swim the polar bear can shake itself like a dog to dry and warm itself quickly.

The white colour of the polar bear also serves as camouflage. This is useful both for hunting of seals and escaping from human hunters. The soles of the bears’ feet have small bumps and cavities that act like suction cups which help to keep them from slipping on the ice.

But most importantly, polar bears have the ability to slow down their metabolism, after 7-10 days of not being able to feed, for whatever reason and at any time of year, until food becomes available again. This helps them adapt to the uncertainties of food availability in the Arctic. In comparison, black or brown bears can slow down their metabolism only in response to not feeding in the late autumn, just before they enter their dens for the winter. If food is not available in spring or summer, they will simply starve to death.

3. How are polar bears adapted to swimming?

Polar bears are very well adapted to swimming, with a water-repellent coat and partially webbed feet. Although the longest distance that a polar bear has been recorded swimming is about 100km, they are capable of swimming much further, if necessary. However, this kind of effort requires a lot of energy, which is why polar bears rarely swim such long distances. The longest a polar bear in the wild has been timed holding its breath while diving is 72 seconds.

4. Why are there no polar bears in Antarctica?

Polar bears evolved relatively recently (about 200,000 years to possibly as long as 500,000 years ago) from grizzly bears somewhere off eastern Russia or the Alaskan Panhandle. They depend on sea ice for their primary habitat for their food (mainly ringed seals and bearded seals). As the world's oceans have never been frozen from the north to the south, polar bears simply didn’t have the possibility to reach the Antarctic, although it would have been a perfect home for them.

5. How long do polar bears live?

Polar bears have a normal life span of about 25 years for males and 30 for females, although they may live longer. In captivity, some polar bears have survived for longer than 40 years.

Source and more information about polar bears: IUCN Polar Bear Specialist Group