Polar bear’s zoological name is Ursus maritimus, which means “sea bear”. Polar bears are restricted to icy Arctic region where temperature falls as low as -50°C. They are well adapted to the freezing temperatures, which restricts them to the circumpolar region where 19 populations exist. Over forty percent of polar bears live in the north of Canada.
Polar bears have the distinction of being the largest land carnivores. Adults are about 8 ft long and weigh 300-700 kg, larger than the fearsome grizzly bear. Fifty percent of body weight is due to fat and blubber that makes 10 cm thick layer under their blackish skin.
Polar bear’s whitish fur is extremely dense, oil coated and water repellent, so much so that water does not reach the skin even when they are swimming in sea. Each hair is transparent with a hollow core that refracts and reflects visible light to make the fur appear snow white.
Polar bear paws measure up to 12 inches and have fur and foot pads with papillae on the soles that help distribute weight of body over larger area and to get firm grip on the slippery ice surface. Polar bear claws are two inches long, curved, sharp and strong to prevent slipping on ice and to help in climbing over icy slopes.
Polar bears are strong swimmers and divers which enables them to swim from one iceberg to another and to hunt seals in sea. They can also swim underneath ice sheet in search of food. Polar bears can swim continuously for hundreds of kms at speeds of about 10 km/hr. They are known to be the only terrestrial animals to be very comfortable in the sea, often covering long distances with ease helped by their fatty body and waterproof fur. There are instances of polar bears covering marathon 400 km by swimming continuously for several days without finding a resting place. These long journeys enable bears to reach long distances via the sea route.
Polar bears do not hibernate in true sense in dens like the brown and black bears do. Instead they remain active throughout winter in spite of freezing cold. However, pregnant females dig a protective den in snow where they give birth to 2-3 cubs in November- December. During denning cubs subsist on mother’s milk and mother on her fat reserves. They remain in the den for about three months, safe and protected from the cold and wind. Mother bears do not enter deep hibernation because they need to maintain higher body temperature in order to meet the demands of pregnancy, birth, and nursing. Polar bear families generally emerge from their dens in March-April when the cubs are strong enough to survive outside.
Polar bears hunt their favourite prey, the seals while they are basking in the sun or through the breathing holes made by them in the ice sheet. They also eat plants and berries and also hunt fish and other animals. They also act as scavengers of dead whales, walrus or fish. Generally they consume skin and fat of the prey in order to accumulate reserve fat in the body. No other animal can eat and digest such fat-rich diet as do these bears.