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Polar bears (Ursus maritimus) are of special interest because of their large size, white color and position as the top trophic level carnivore in the remote arctic environment. They occur only in the northern hemisphere nearly always in association with sea ice.
General description: Polar bears and brown bears evolved from a common ancestor and are still closely related, as demonstrated by matings and production of fertile offspring in zoos. Polar bears are similar in size to large brown bears. Adaptions by the polar bear to life on sea ice include a white coat with water repellent guard hairs and dense underfur, short furred snout, short ears, teeth specialized for a carnivorous rather than an omniverous diet, and hair nearly completely covering the bottom of the feet. Cubs weigh between 1 and 2 pounds (0.5-0.9 kg) at birth. An extremely large adult male may weigh 1,500 pounds (680 kg). Most mature males weigh between 600 and 1,200 pounds (273-545 kg), and are between 8 and 10 feet (2.4-3.0 m) in length. Mature females weigh 400 to 700 pounds (182-318 kg).
