Polar bears hind limbs are longer than the forelimbs. This makes the large, muscular hind end stand higher than the shoulders. Although both there hind and forelimbs are very large and stocky. They have hug

Polar bears are in the class mammalian, so therefore they are mammals. The characteristics of mammals are: They are endothermic which means they have a relatively high and constant body temperature mostly independent of the surroundings, also known as "Warm-blooded". They have hair, which varies greatly among species. Most have sudoriferus or sweat glands. They all have mammary (milk-secreting) glands. They have sebaceous (fat-secreting) glands, and they give birth to live young.

The total gestation period is about eight months; gestation includes a period of delayed implantation. The fertilized egg divides into a hollow ball of cells one layer thick, which is called a blastocyst, then stops growing and lies free-floating in the uterus for about four months. The blastula then implants in the uterine wall and continues to develop. Delayed implantation assures that the cub is born during the best time of the year for survival and allows the female to get into good physical condition and use her energy for nursing her newborn cubs. The actual embryonic development is estimated to be four months. Once mated, females begin depositing fat in preparation for the cubs. Females need to gain at least 441 pounds for a successful pregnancy. Some females may seek out maternity dens as early as late August, but most enter dens in mid to late October. Dens protect newborn cubs from winter's temperature extremes. Females usually dig dens in snowdrifts on southerly facing slopes. Some dig earthen dens that later become covered by snow. Most dens are on land, within 10 miles of the coast. In some areas, dens are more than 62 miles from the coast. A few polar bears make dens on the sea ice. Most dens consist of a single chamber slightly elevated from a short entrance tunnel. On average, the chamber is 6.6 feet long, 4.9 feet wide, and 3.3 feet high. Polar bears maintain a ventilation hole through the chamber ceiling to provide fresh air. Because of body heat and snow insulation, the den stays warmer than the outside air temperature. Polar bear cubs are born November through January in a den. Mother and cubs emerge from their den in late March or April. Most adult females give birth once every three years. In some populations, birth occurs once every two years. The most frequent litter size is two, followed by litters of one. Litters of three are less common than twins or singles, and litters of four are rare. At birth, polar bear cubs weigh about 16 to 24 ounces and are about 12 inches long. Males are born slightly larger than females. Their fur is very fine at birth, making the cubs look hairless.

e paws compared to their body size, there feet can get up to a foot in diameter. The large paws of a polar bear act like snowshoes, spreading out the bear's weight as it moves over ice and snow. They have 5-toed paws and each toe has a thick, curved, non-retractable claw. The claws are used for grasping prey and for traction when running or climbing on ice. The sole of a polar bear's foot has thick, black pads covered with small, soft papillae or dermal bumps. The papillae create friction between the foot and ice to prevent slippage. Long hairs growing between pads and toes also help prevent slipping on the ice. A polar bear’s head is relatively small compared to its body size; its muzzle is elongated with a slightly arched snout. At the end of the snout is its nose, which is broad and black. Polar bears have 42 teeth, which they use for catching food and for aggressive behavior. They use their incisors to shear off pieces of blubber and flesh. Canine teeth grasp prey and tear tough hides. Jagged premolars and molars tear and chew and they swallow most food in large chunks rather than chewing it up into little pieces like most vertebrates.

A polar bear's hearing is just about as sensitive as human hearing. Humans can hear sounds with frequencies as low as 0.02 kHz and as high as 20 kHz. The eyesight of these bears also is very similar to th

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