Some pilot whales reach 50 years of age. Sharks are the chief natural enemies of dolphins. Some dolphins die after swimming into extremely shallow water and stranding themselves on the shore. The animals cannot live long out of water because their bodies become overheated. Scientists do not know why dolphins beach themselves.
Most beached dolphins die from natural causes.
Most knowledge about the living habits of dolphins comes from aquariums and zoos. Killer whales seem to have the closest-knit groups, most of which consist of from several to 17 or 18 animals. Bottle-nosed dolphins live in groups of about 12. Among some species the groups combine and form herds of 100 to 1,000 dolphins. Adult males and young dolphins move among groups of females with their calves.