Ursus maritimus
Polar bears live within the Arctic Circle on ice covered waters from Canada to Norway. They are the largest living land carnivores, adult males can grow to 2.6m tall (8 foot 6 inches). The polar bear's distinctive white fur, long neck and small head and ears make it the most easily identifiable of the bear family. It has large paws that help to stop it sinking into deep snow. They have non-retractable claws and wrinkled soles to their feet which stop them slipping on the ice.
Polar bears spend much of the Spring and Autumn hunting for ringed and bearded seals, walruses and even small whales on the pack-ice. They are well camouflaged and wait patiently at breathing holes in the ice for their prey to surface before pouncing. They also hunt for seal-pups that are hidden under the ice in dens, crashing through the icy roofs and grabbing the pups before they escape into the water. During the Winter and Summer when hunting is difficult they are able to slow their metabolism and enter a hibernation-like state.
Polar bears are extremely good swimmers. Their large paws and powerful forelimbs help them to swim great distances between ice-sheets. Their thick fur traps a layer of insulating air close to their skin and prevents them loosing too much heat in the freezing water. Some scientists even consider them to be marine mammals.
Female polar bears normally produce twin cubs in December or January, giving birth in a snow den. Sometimes single cubs or triplets are born. She will look after them for 2.5 years, initially suckling them in the den before leading them out onto the ice to begin to learn to hunt. Only 1 in 4 cubs will grow to adulthood.
Polar bears are extremely susceptible to the effects of global warming. They are dependent on the sea-ice for their hunting grounds. Over the last 50 years scientists measuring the extent of the sea-ice and its duration have observed decreases in both as the mean surface temperature of the Earth has increased. In September 2007 the extent of the Arctic sea-ice was 41% less than the historic average recorded between 1978 and 2000 (http://nsidc.org/news/press/2007_seaiceminimum/20070810_index.html). This loss of sea-ice has resulted in a reduction in the area of sea-ice on which polar bears can hunt and a shortening of the hunting season. Bears are increasingly suffering from malnutrition. In some areas they are forced to look for food in rubbish dumps which brings them into close contact with people.
