Polar Bears and Seals

The largest terrestrial carnivores on the planet and ranging throughout the Arctic, polar bears are superbly adapted to their frigid home. Their complete dependence on ice for feeding, breeding and traveling makes them extremely vulnerable to global warming. Polar bears' most important prey are ringed seals and bearded seals, and on average they need to eat about 45 seals a year to survive.

Ringed seals give birth and raise their pups in snow lairs on both pack and land-fast sea ice and can inhabit the fast ice even in the winter because of their ability to scratch open and maintain breathing holes with the heavy claws on their flippers. Their greatest vulnerability apart from the loss of ice is likely to be the increased spring rainfall which can lead to the collapse of snow dens and the death of pups. Bearded seals are found in shallower waters and pup mainly on floating pack ice. Reductions in the amount and stability of pack ice, as well as its earlier break up in the year will affect all the ice-associated seals including ribbon and spotted seals, but may be particularly negative for harp and hooded seals as their pups need a longer period of stable ice to rest and learn to hunt on.

Significant reductions in numbers of seals will certainly be bad for polar bears, but of even greater consequence is the early break up of floating ice. Sea ice is most important as a platform for seal hunting. In the more northerly areas some bears spend all year on sea-ice of one sort or another. In southern Arctic areas, such as Hudson Bay after all the ice melts, bears have to spend weeks or months on land fasting before the fall freeze. Warming in the Western Hudson Bay has already resulted in sea ice break-up 3 weeks earlier than in the 1970s. Thus polar bears in this region are now unable to get out on the ice and hunt at the most critical time of year – the late spring, when seal pups are most abundant and easy to catch.

Scientists have shown that female polar bear body weights in this area are progressively declining, and that fewer cubs are surviving. The ultimate consequence will be reduced numbers of adult bears. What is already happening in Hudson Bay does not auger well for the rest of the Arctic’s 20-25,000 polar bears. In 2007, the US Geological Survey analyzed all the available scientific data on polar bears and climate change and came to the conclusion that “projected changes in future sea ice conditions, if realized, will result in loss of two thirds of the world’s current polar bear population by the mid 21st century.” Read more on Arctic wildlife and biodiversity.