Polar bears have very good eyesight and hearing although their sense of smell is their most highly developed sense. These remarkable bears have a transparent eyelid (nictitating membrane) that work like a pair of sunglasses filtering out the excessive brightness of snow and sun. They also work as waterproof goggles underwater.
Polar bears have 42 teeth and are well adapted to their carnivorous diet. Their canines are the largest and longest of any other bear. They use their extremely sharp carnassials and molars for shearing and biting food.
Longevity:
In zoos, polar bears may have a life expectancy of 23 years.
Behavior:
Polar bears are solitary animals and mating occurs during the summer season. At the end of the Polar winter, which is in March or April, females give birth to between one and four cubs who stay with their mother for one or two years.
Because of the Arctic or midnight sun, polar bears are active any time of the day or night. On bitterly cold days, they might dig a hole, curl up and even cover their noses with their paws to keep warm. In warmer weather they might also burrow into the earth to keep cool.
Adaptations:
Contrary to popular belief, the Polar Bear's fur neither acts like a fiber optic nor "solar heating" system. The UV light that is absorbed by the keratin guard hairs is limited to the outer (peripheral) inch of the hair shaft, and is quickly dissipated back to the ambient cooler surroundings and not transmitted to the bear's skin.
Considering their large size, polar bears are surprisingly fast. On land, they can outrun a reindeer for short distances, moving at speeds of 25 mph. In water, polar bears can swim for considerable distances at a speed of up to six miles per hour. They paddle with their front feet and use their back feet as rudders.