Polar Bear Characteristics

Physical Characteristics

• Polar bears are the largest living species of bear and land carnivore, with males typically measuring 200-250 cm (6.6-8.2 ft) in length and weighing 300-800 kg (660-1,760 lb).
• Females are smaller, measuring 180-200 cm (5.9-6.6 ft) in length and weighing 150-300 kg (330-660 lb).
• Males have proportionally larger heads than females.
• Adults can stand 130-160 cm (4.3-5.2 ft) tall at the shoulder.
• The tail is 76-126 mm (3.0-5.0 in) long.

Diet and Teeth

• Polar bears have a more carnivorous diet than brown bears, with longer, sharper, and more spaced-out canines.
• They have smaller, more pointed cheek teeth (premolars and molars) and a large space or diastema between the canines and cheek teeth.
• This adaptation allows them to better bite into prey.

Paws and Claws

• Polar bears have large paws, with the front paws being broader than the back.
• The feet are hairier than in other bear species, providing warmth and friction when stepping on snow and sea ice.
• The claws are small but sharp and hooked, used for snatching prey and climbing onto ice.

Coat and Insulation

• The coat consists of dense underfur around 5 cm (2.0 in) long and guard hairs around 15 cm (5.9 in) long.
• The outer surface of the hairs has a scaly appearance, and the guard hairs are hollow, trapping heat and allowing the animals to float in the water.
• The transparent guard hairs forward scatter ultraviolet light between the underfur and the skin, leading to a cycle of absorption and re-emission, keeping them warm.
• The fur appears white due to the backscatter of incident light and the absence of pigment.

Thermoregulation

• Polar bears have a 5-10 cm (2.0-3.9 in) thick layer of fat underneath the skin, providing both warmth and energy.
• They maintain their core body temperature at about 36.9 °C (98 °F).
• Overheating is countered by a layer of highly vascularized striated muscle tissue and finely controlled blood vessels.

Other Adaptations

• The eyes are close to the top of the head, allowing them to stay out of the water when swimming at the surface.
• They are relatively small, which may be an adaptation against blowing snow and snow blindness.
• Polar bears are dichromats, lacking the cone cells for seeing medium, mainly green, wavelengths.
• They have many rod cells, allowing them to see at night.
• The ears are small, allowing them to retain heat and not get frostbitten.
• They can hear best at frequencies of 11.2-22.5 kHz, a wider frequency range than expected.
• The nasal concha creates a large surface area, allowing more warm air to move through the nasal passages.
• The olfactory system is also large and adapted for smelling prey over vast distances.