Sea otters usually do not migrate. They seldom travel far unless an area has become overpopulated and food is scarce. They are gregarious and may become concentrated in an area, sometimes resting in pods of fewer than 10 to more than 1,000 animals. Breeding males will drive nonbreeding males out of areas where females are concentrated. In some areas, the nonbreeding males will concentrate in "male areas" which are usually off exposed points of land where shallow water extends offshore. Bald eagles prey on newborn pups and killer whales may take a few adults, but predation is probably insignificant. Many sea otters live for 15 to 20 years.