whale

The male narwhal, a toothed whale, has a spiral tusk up to 2.7 m/9 ft long. The tusk is actually an extended tooth which grows out of a hole in the upper lip. The tusk is not used as a weapon, although it may be used to dominate other males and to impress females.

A humpback whale breaching (leaping clear) out of the water. The humpback whale (Megaptera novaeangliae), an endangered species, is found principally in the North Atlantic and North Pacific Oceans.

The killer whale or orca, a hunter of seals and penguins, is found in all the oceans of the world, and can grow to a length of 9 m/30 ft. Many are in captivity. This whale was photographed in the aquarium at Stanley Park, Vancouver, Canada.

Any marine mammal of the order Cetacea. The only mammals to have adapted to living entirely in water, they have front limbs modified into flippers and no externally visible traces of hind limbs. They have horizontal tail flukes. When they surface to breathe, the hot air they breathe out condenses to form a ‘spout’ through the blowhole (single or double nostrils) in the top of the head. Whales are intelligent and have a complex communication system, known as ‘songs’. They occur in all seas of the world.

The order is divided into two groups: the toothed whales (Odontoceti) and the baleen whales (Mysticeti). Toothed whales are predators, feeding on fish and squid. They include dolphins and porpoises, along with large forms such as sperm whales. The largest whales are the baleen whales, with plates of modified mucous membrane called baleen (whalebone) in the mouth; these strain the food, mainly microscopic plankton, from the water. Baleen whales include the finback and right whales, and the blue whale, the largest animal that has ever lived, of length up to 30 m/100 ft.

Whales have been hunted for hundreds of years (see whaling); today they are close to extinction. Of the 11 great whale species, 7 were listed as either endangered or vulnerable in 1996. Whale-watching, as an economic alternative to whaling, generated US$121 million worldwide in 1994.

Description The whale's skin is hairless. Below the skin is a thick layer of blubber, fatty tissue. Movement is by the tail and flukes. Whales typically give birth to a single young at a time. The young are born alive, after a gestation period of 10-12 months. Most whales are inoffensive creatures and swim in herds; they have been known to follow a confused leader onto a beach. Once stranded on shore they die by suffocation, their own weight crushing the lungs.

Varieties Toothed whales comprise 66 species, of which the largest is the sperm whale Physeter catodon. A waxlike substance, spermaceti, is used by the whale to enable it to dive; cold water is taken into the blowhole cooling the spermaceti, which becomes denser, and the whale dives. To surface, the whale directs blood towards the spermaceti, which then warms and becomes less dense.

The killer whale is a large member of the dolphin family (Delphinidae), and is often exhibited in oceanaria. Killer whales in the wild have 8–15 special calls, and each family group, or ‘pod’, has its own particular dialect: they are the first mammals known to have dialects in the same way as human language.

Baleen whales comprise 10 species, in three families: rorquals, right whales, and grey whales. The common rorqual Balaenoptera physalas is slate-coloured, and not quite so large. Right whales of the family Ballaenidae have a thick body and an enormous head. They are regarded by whalers as the ‘right’ whale to exploit since they swim slowly and are relatively easy to catch. The Northern right whale is close to extinction – in 1999 there were fewer than 325 remaining. The blue whale Sibaldus musculus, one of the finback whales (or rorquals), is 31 m/100 ft long, and weighs over 100 tonnes. It is the largest animal ever to inhabit the planet. It feeds on plankton, strained through its whalebone ‘plates’. The bottle-nosed whale occasionally visits British waters. The white whale is found mostly off Labrador and Canada. Of the whalebone or right whales the most important formerly were the Greenland whale Balaena mysticetus and the Biscayan whale or nordkaper Eubalaena glacialis.

Beaked whales comprise 18 species that are found in all oceans. They are a little known group of medium-sized whales, with narrow snouts resembling htose of dolphins. A new species of beaked whale was discovered in 1996, in Chilean waters. The melon-headed whale Peponocephala electra, like the other beaked whales, is a deep-living whale that feeds on squid. It is estimated to be 5 m in length and weighs around 2 tonnes.

See also bowhead whale.

A third order, the Archaeoceti, is known only from fossils. Palaeontologists from the USA and Pakistan discovered 1993 a fossil whale with legs. The fossil, called Ambulocetus, is 50 million years old and about the size of a male sea lion. It was able to walk on land but spent most of its time at sea.

Feeding The humpback whale Megaptera novaeangliae catches krill by encircling them and blowing bubbles to concentrate them into a smaller central area. It then rises through the krill to eat it.

Sperm whales feed mainly on squid, for which they can dive to 1,000 m/3,280 ft (one dive was recorded at over 3,000 m/9,841 ft). A dive may last for up to an hour, although they are more typically around ten minutes. Exactly how the sperm whale catches squid is unknown, although the squid frequently leave sucker marks on the whales' heads.