Snow or earthen dens, adaptive fur, and blubber protect carnivorous polar bears from drastic Artic temperatures. Only 1/3 of their time is spent hunting food, such as seals, whales, walruses and fish. Their steady, lumbering walk reaches speeds of 3.4 mph; they run nearly 25 mph (short distances;) they powerfully swim for several hours. Their eyesight and hearing are similar to those of man. Chemical spills, starvation, parasites and slow reproductive maturity threaten their survival.