Whale, a member of a group of water animals, some species of which are the largest animals ever known. Although it lives in water all its life and is shaped like a fish, the whale is a mammal. It is warmblooded, breathes air, bears living young, and suckles its young with milk.

Sperm whalesSperm whales have been known to ram and sink whaling ships.

Whales have been hunted for centuries for food and other uses. Whale blubber, a thick layer of fatty tissue under the skin, was a primary source of oil before the extensive use of vegetable oils and petroleum. Baleen, or whalebone, a horny substance found in the mouths of some kinds of whales, was used for making corset stays and fans before the invention of celluloid and other plastic substances.

There are many kinds of whales, ranging in size from the 5-foot (1.5-m) harbor dolphin to the blue whale, which may reach a length of more than 100 feet (30 m). The largest whales may weigh up to 140 tons. Whales are found in all seas and in many coastal waters.

How Do Whales Differ from Other Mammals?

All whales are mammals, but they differ from other mammals in some obvious ways.

Most mammals have four legs. A whale has no hind legs. And instead of front legs, a whale has flippers. These help the whale steer and keep its balance. A whale also has a tail fin that spreads out into two wings, or flukes. On its back, this killer whale has a triangular-shaped fin, called a dorsal fin. Fish have fins—but most mammals do not.

Most mammals have hair on their bodies. But toothed whales have only a few bristles—or none at all. Many toothed whales have long snouts, called beaks, and bulging foreheads, or melons.

Whales are like other mammals in some ways, however. They have lungs and breathe air—just as you do. They are warm-blooded, or make their own body heat. Babies nurse on their mothers’ milk