large species of sturgeon (q.v.).

Belugas are about 1.5 metres (4.9 feet) long at birth and grow to a length of about 4 metres. Newborn calves are gray to brown, but their colour fades with age until they become completely white after attaining sexual maturity at four to five years old. Adults have broad flippers with upward-curving tips, but there is no dorsal fin. Belugas have a rounded forehead and extremely plastic facial features, enabling the whales to alter the external shape of their head at will.

Arctic populations of beluga whales are at home in pack ice but must migrate to warmer waters when the sea freezes over completely. They usually live in groups of 5 to pods of more than 1,000, feeding on fish, cephalopods (cephalopod), crustaceans (crustacean), and worms.

In the Arctic the beluga is hunted as food for humans and dogs. During the 19th and early 20th centuries, it was taken commercially for its oil, flesh, and hides, which provided industrial leather, belts, and shoelaces. The beluga population in the Gulf of St. Lawrence (Saint Lawrence, Gulf of) was nearly exterminated for its hides, and some other beluga populations are endangered by pollution.

Beluga whales are related to the narwhal, and together these two species constitute the family Monodontidae of suborder Odontoceti (the toothed whales). The beluga's generic name comes from the Greek word for dolphin, delphinos, combined with apteron, alluding to its lack of dorsal fin. The specific epithet leucas is derived from the Greek leukos, meaning “white.” The common name, sometimes spelled belukha, is derived from the Russian belyi, again meaning “white.” Beluga is also a common name for the unrelated great white sturgeon of caviar fame.