Polar Bears of Churchill – On Hudson Bay
By mid-November, ice covers much of the western coast of Hudson Bay. Most of the bears, young and old, have returned to the ice, but their work has just begun. While seals are available, hunting is still difficult.
In order to survive these extreme climates polar bears have developed complex physical adaptations. By late October, the bears’ undercoat gets much thicker, so thick that it gets very hard to find their skin through it. Researchers estimate that a bear’s coat consists of almost ten thousand hairs per square inch by mid-winter. Obviously, their cold resistance is considerable.
This is not to say, however, that polar bears are completely resistant to the arctic winter. Strong winds and cold ambient air temperatures still affect them. The guard hairs keep a warm layer of air next to the skin and strong winds penetrate these hairs, undermining their insulative value. For this reason, they often wait out the winter storms, taking shelter on the lee side of snow banks and ice ridges. Sometimes, bears will stay motionless for days, only to rise and shake away a layer of snow as the storm breaks.
As well, water affects their ability to maintain heat. This affect is very noticeable during Churchill’s bear season. Polar bears go to some incredible efforts to avoid getting wet! They will divert their path to avoid the many tundra ponds near Churchill. In fact, the bulk of visiting polar bears do not arrive in the Churchill area until many of the inland ponds have a fresh layer of ice.
However, the anticipation of winter is strong and testing ice is a common pass time during bear season, sometimes ending with the groan and crack of breaking ice and a very wet bear. On a warm day this is welcome, on cold days it is less than comfortable. Absorbing heat twenty five times faster than air, water can soak to the bear’s skin and cools it quickly. To a large male with four inches of fat, this may not matter but to a younger, thinner bear, it could be fatal. To avoid this, their guard hairs are oily and shed water quickly. Emerging from the ocean or a partially frozen tundra pond, bears quickly shake excess water from their coat.
In a further adaptation to life on the ice, polar bears are almost completely furred, even much of their paws are covered. Their foot pads are also covered with little bumps. These bumps, or papillae, provide extra traction while traversing ice ridges on the rugged sea ice. Finally, their claws, short and strong, are also sharply curved; providing even greater ability to navigate the frozen ocean.
As with all arctic animals, their appendages, mainly their ears and tail, are smaller than other bears. This follows the idea that less surface area results in less heat loss. Polar bears emanate almost no heat, only their black noses and a wisp of breath showing up on infrared or heat sensitive cameras.