The polar bear (Ursus Maritimus) is almost entirely carnivorous, unlike other relatives in the bear family. It is undoubtedly at the top of the food chain in the arctic regions. The diet is mostly ringed seals with the occasional bearded seal thrown in for variety. To hunt seals, the bear waits motionless beside the seal's breathing hole. When the seal surfaces, the bear either bites the head, or swats the seal with its paws, flipping the seal out onto the ice. The bear may also stalk the seals, either in the water or on land, or use its front paws to break through the roof of a birth lair, where a mother seal and her young are. Polar bears will scavenge on carcasses of whales and walruses, and, if seals are in shortage, are known to hunt and feed on reindeer, small rodents, sea birds, and of course humans.
The fact is, polar bears are the most aggressive bears towards humans. Compared to other bears, polar bears are more willing to consider humans as prey. This means that when a polar bear does attack a person, they are not likely to leave until either the person or the bear is dead. Young animals and mothers with cubs are the usual culprits when human attacks have been documented. They're also the chief scavengers (among polar bears) of human dump sites. Both groups tend to be thinner and hungrier; subadults are inexperienced hunters, and females with cubs must feed themselves and their young
Polar bears are amazing swimmers. Their feet are partially webbed, they have long necks to keep their noses out of the water, and they actually float without any effort, due to the amount of fat they store on their bodies. A polar bear usually swims around 3 mph, but is capable of swimming 6 mph for over 10 hours without pausing to rest. Polar bears can also run pretty fast, reaching speeds of 25 mph for short distances.
Polar Bears are huge animals. Males grow to weigh 1100 to 1300 pounds, and females average about 700 pounds. There is a record of one adult male weighing 2200 pounds, over one ton! They generally stand about 3 feet tall at the shoulder and reach a length of 8 to 11 feet. They live about 25 years in the wild, considerably less in captivity.
Polar bears mate in late spring and early summer. Through a remarkable process known as delayed implantation, however, the fertilized ovum doesn't actually attach to the uterine wall until September. The purpose for this is believed to be that if the mother is unable to store enough fat to survive the winter, the embryo will not implant, and will simply be reabsorbed into the mother's body. The mother enters the den in October or November, and the cubs are born in the next two months, while the mother is still hibernating. The cubs, usually 2 or three are about the size of a chipmunk and suckle their mother, who remains asleep until she breaks out of the den in March or April. By then the cubs will each weigh 22 to 35 pounds. What a concept! Go to sleep and wake up with two kids.
Only pregnant polar bears actually hibernate. Other bears will enter a shelter and sleep for a short period of time, but the mothers are the only ones who remain there for a long time. During hibernation, the bear's heart rate will drop from 40-70 beats per minute to about 10 beats per minute. Unlike many animals, however, the polar bear's body temperature only lowers slightly. This high body temperature is important in that it keeps the temperature in the den above freezing for when the cubs are born. The bear passes neither fecal or urea waste during hibernation, but has developed a unique process of recycling the urea into usable proteins. The urea buildup would kill most animals within two weeks.
The polar bear population is now around 30,000 individuals, up from only 10,000 in 1968. The increase is due to government regulations on hunting. There is concern, however, that due to global warming, the southern range of the polar bear is being pushed northwards, and populations may suffer.