Relatives of dolphins and toothed whales, porpoises are small, shy sea mammals that swim fast in the sea. Many porpoises are threatened by human activities, such as fishing and pollution.
Porpoises and dolphins both evolved from a common ancestor around ten million years ago. Both animals have a sleek, streamlined body, a dorsal fin, flippers, and a blowhole on the top of their head. However, porpoises have a short, rounded snout, instead of the dolphin’s long, beaklike snout. Porpoises also have flat, spade-shaped teeth, while dolphins have cone-shaped teeth. Both dolphins and porpoises feed mainly on fish and use their teeth to hold their preyrather than for cutting or chewing their food. Porpoises do not seem to help each other catch food, as do many species of dolphins. Harbor porpoises can
