Dolphins-aquatic mammals of the suborder toothed whales. Dolphins, like all cetaceans, breathe air periodically floated to the surface. Feed mainly on fish and squid, although some prefer the shrimp and other crustaceans, and killer whales also eat sea turtles, aquatic mammals and birds. The majority of dolphins, males are larger than females and in some species are distinguished from them by higher dorsal fin. Known individuals under the age of 50 years, although in most species the maximum life expectancy of 20-25 years.