Currently only classed as vulnerable, although reclassification as endangered is being discussed, the Polar Bear, which has the scientific name of Ursus maritimus (marine bear, a name it received owing to its excellent ability to swim), is the largest of all land living carnivores.
Adult males can reach a length of up to 2.6 m (8.53 ft) and weigh up to 600 kg (1,322.77 lb, or 94.5 st). Females tend to be considerably smaller at lengths of around 2.1 m (6.9 ft) and weighing in at up to 300 kg (661.39 lb, or 47.25 st). A pregnant female with plenty of stored fat can, however, weigh more than 500 kg (1,102.31lb, or 78.74 st).
Immediately recognisable due to the distinctive white appearance of their fur (which is, in fact not white, but colourless), Polar Bears have longer necks than other bears, and their elongated heads feature comparatively small ears. The black tip of the Polar Bear's nose and its footpads (which are also black) are the only parts of its body that have no fur.
Extremely strong-limbed, Polar Bears use their huge forepaws for paddling. The toes of this gorgeous creature are not webbed, but are designed to to walk on snow and ice. Non-retractable claws dig into snow not unlike ice-picks, and small indents and projections on the soles of the bear's feet help the animal to walk on icy surfaces without slipping by acting like suction cups.
Range, Habitat and Biology
Polar Bears are found on ice-covered waters throughout circumpolar Arctic regions, from Denmark (or to be more precise, Greenland) and and Norway through the former USSR to parts of the United States and Canada. Canada's James Bay - London, by the way, is on roughly the same latitude - is the furthest south polar bears can be found throughout the year.
As the ice cover extends further to the south during the winter months, Polar Bears will often move as far south as the northern Bering Sea and Newfoundland. They rarely enter central polar basin areas, as the year-round, thick ice means there is little food for them here.
The annual ice close to the coastlines of islands and continents represents the Polar Bear's preferred habitat, as this is where the largest numbers of their favourite prey, Ringed Seals (scientific name Phoca hispida) can be found.
Living solitary lives for the best part of the year, except when breeding or in family groups, stocks - or populations - of Polar Bears are distributed all over the Arctic, with undefended home ranges up to 300,000 sq km (115,830.65 square miles) in size often overlapping.
Able to detect prey up to a metre (3.28 ft) under compacted snow and up to 1 km (0.62 miles) away thanks to their extremely heightened sense of smell, Polar Bears feed predominantly on Ringed Seals, although they will not refuse a Bearded Seal (scientific name Erignathus barbatus) either. Seals are usually captured as they come to the surface of water holes to breathe, although the bears will also hunt them down in their lairs under the snow, especially when young seals are being nurtured there. If and when the opportunity arises, Polar Bears will also feed on belugas, narwhals, seabirds, walruses and waterfowl.
While there is plenty of food around, Polar Bears can devour remarkably large amounts of food very quickly. When little food can be found, this animal has the unique ability to enter a hibernation-like, slowed down metabolic state. The ice in Hudson Bay, for instance, completely disappears from mid-July right through to mid-November. This means pregnant females typically do not feed for a total of up to eight months. They will metabolise stored protein and fat reserves, as well as recycling metabolic by-products. Particularly cold weather may also prompt this majestic animal to fast. Energy is often conserved during such periods by the bears retreating into temporary dens.
The mating season of Polar Bears ranges from late March into May. As the females nurse cubs for two and a half years, they are only available for mating once every three years. In order for ovulation and fertilisation to be stimulated (a process known as induced ovulation), females must mate over and over again for several weeks. Breeding pairs subsequently stay together for up to two weeks or so to ensure success. If the male is displaced, the female may mate with other males during this period.
The implantation of fertilised eggs is then delayed until some time between mid-September and mid-October. Two to three months later, the female will give birth - litters may consist of one, two or occasionally three cubs - in a snow den. Each cub will weigh approximately 0.7 kg (1.54 lb) at birth. Although they look like miniature versions of their parents, their fur is much thinner to begin with. All being well, assuming they survive the first few years of their lives, the cubs have an overall life expectancy of 25 to 30 years.
Since hunting - which at one point drove Polar Bears to near extinction - is regulated, the main threats to populations are poaching, pollution, disturbances generated by industrial activities and - first and foremost - large scale ecological changes brought on by climate changes.
While long term effects of climate changes are as yet unclear, it is certain that even minor changes have a profound impact on the lives of these animals. More snow, for instance, could result in the bears having problems hunting for seals in their lairs. This would obviously affect survival rates of both cubs and adult bears. Less snow, and perhaps increased rainfall, on the other hand, may result in seal populations being drastically reduced as lairs may not be thick or deep enough to protect their cubs, or they may collapse, killing the cubs outright.
Fewer seals obviously mean less prey and lower survival rates for Polar Bears. Increases of overall temperatures are also likely to have a serious effect. Polar Bears are perfectly adapted to the freezing temperatures of the Arctic. Warming of their habitat will not only affect their ability to create dens, it may also cause them to die as a result of overheating. Receding ice cover forces more and more bears onto solid ground, where food is not as easily found, often meaning bears eventually succumb to starvation.
The reduction of sea ice also means many bears get stranded on floating ice in their search for food. While they are good, strong swimmers, even Polar Bears can only swim so far, and many of them are already found dead as a result of drowning.
To make matters worse, big oil companies now plan to take advantage of the reduction in sea ice by oil drilling in the Arctic. This will put the already fragile habitat of Polar Bears at an even greater risk. To protect this beautiful creature, this must not happen, and political leaders need to be pressured into protecting the Arctic.
Greenpeace are sponsoring a petition to this effect. The names of people signing this petition will be entered onto a scroll, which, when completed, will be placed onto the North pole's seabed with a flag to demand the Arctic remains off-limits to industrial fishing and oil drilling. Readers can sign this petition at Care2
More detailed, scientific information on Polar Bears can be found at Polar Bears International.