Whales

Home > Plants and Animals > Animals > Vertebrate Zoology

whale aquatic mammal of the order Cetacea, found in all oceans of the world. Members of this order vary greatly in size and include the largest animals that have ever lived. Cetaceans never leave the water, even to give birth. Although their ancestry has been much debated, DNA studies and skeletal evidence from extinct early whales indicate that whales evolved from the ancestors of artiodactyls, a group that includes hippopotamuses, cows, pigs, and deer.

Characteristics and Behavior

Like other mammals, whales breathe air, are warm-blooded, and produce milk to feed their young. Their adaptations for aquatic life include a streamlined form, nearly hairless skin, and an insulating layer of blubber, which can be as thick as 28 in. (70 cm) in some Arctic species. The forelimbs of whales are modified into flippers, and the hind legs are reduced to internal vestiges. Many species possess a dorsal fin. The tail is flattened into horizontal flukes and is used for propulsion. The head is very large, with a wide mouth and no external neck.

Whales have one or two nostril openings, called blowholes, located far back on the top of the head; the nostril valves close and the lungs compress when the whale dives. Most whales must surface every 3 to 20 min to breathe, but some, like the sperm whale , can remain submerged for more than an hour. Spouting occurs when the whale surfaces and clears water from its blowhole along with any moisture trapped in its air passages. The shape of the spout is characteristic of each type of large whale. Whales have small eyes, designed to withstand great pressures, and most species have good vision. Their hearing is also excellent. Many cetaceans have highly convoluted brains larger than those of humans, and whales are believed to be extremely intelligent.

Most large whales travel in small schools, or pods, but some, like the fin whale, swim alone or in pairs; small cetaceans form schools of up to several thousand individuals. Most large whales are found in open ocean, where they migrate thousands of miles between feeding and breeding grounds. Dolphins frequently live in coastal waters. A few dolphin species are found in tropical rivers. Females of most species give birth to a single calf every two to three years. Gestation periods range from 9.5 to 17 months. The newborn calf is pushed to the surface by the mother or by another adult; it is able to swim almost immediately and is nursed for 6 to 12 months. Some large whales are believed to have lived 100 years or more in the wild.

Types of Whales

There are two major groups of whales—the toothed whales (suborder Odontoceti) and the toothless baleen whales (suborder Mysticeti).

Toothed Whales

Toothed whales include two families that are widely distributed, the beaked and bottlenose whales (family Ziphiidae) and the sperm whale, or cachalot (family Physeteridae); the beluga , or white whale, and the narwhal (family Monodontidae), small polar whales with no dorsal fin and only a few teeth; the river dolphins (family Platanispidae), which inhabit muddy rivers of India and South America; and several families better known as ocean dolphins and porpoises . The killer whale and pilot whale are types of dolphin. The white whale Moby-Dick, of Herman Melville 's novel, was not a beluga but a sperm whale with prominent white features.

Toothed whales range in length from 4 to 60 ft (1.3-18.5 m). They catch fast-moving prey, like fish or squid. Many species use echolocation (sonar) for underwater navigation and hunting. They have a single blowhole and a wide throat to accommodate large prey. Some of the larger ones, like the sperm whale, can dive as deep as 1 mi (1.6 km).

Toothless Whales

There are three families of baleen whales: the right whale family (Balaenidae), including the bowhead, or Greenland whale; the gray whale family (Eschrichtidae), with a single species ( Eschrichtius robustus ) found in the N Pacific Ocean; and the rorqual family (Balaenopteridae). Rorquals, the most familiar of the large whales, have large, pouchlike throats with furrows running from mouth to belly. The family includes the humpback whale, the sei whale, the minke whale, the Bryde's whale, the fin whale (or common rorqual), and the blue whale , which can grow to a length of 100 ft (30 m) and a weight of 150 tons.

Baleen whales are large species, usually over 33 ft (10 m) long. They are filter feeders, living on shrimplike krill, plankton, and small fish. They lack teeth but have brushlike sheets of a horny material called baleen, or whalebone, edging the roof of the mouth. With these strainers and their enormous tongues, tons of food can be separated from seawater. Baleen whales have narrow throats and paired blowholes. Male humpbacks produce a repeated pattern of sounds called a song during the mating season; the purpose is not clear, as all males in a group sing basically the same song.

Whaling

All species of large whales have been drastically reduced in numbers by centuries of intensive whaling. An indefinite ban by the International Whaling Commission on commercial whaling of all large whales gradually went into effect following the 1984-85 season, and large portions of ocean have been designated whale sanctuaries. With these and various other protective efforts, some species have begun to return to acceptable numbers, but others, especially the right and blue whales, are still rare and endangered. After decades of protection the number of E Pacific gray whales seems to have returned to its estimated prewhaling level. Only the small minke whale exists in populations great enough for sustainable whaling to be considered. Whale products include whale oil , sperm oil , spermaceti , ambergris , and whalebone, as well as meat, bone meal, and liver oil. Natural and synthetic materials have replaced all whale products in the United States. See separate entry on whaling for more information.

Classification

Whales are classified in the phylum Chordata , subphylum Vertebrata, class Mammalia, order Cetacea.

Bibliography

See R. Ellis, The Book of Whales (1980) and Dolphins and Porpoises (1989); L. Watson, Sea Guide to Whales of the World (1981).

whale, the most charismatic of marine mammals. Whales are a popular tourist attraction and to see a whale breaching is an exciting moment. They belong to the order Cetacea, which consists of about 76 species of whales, porpoises, and dolphins. There are two main groups, baleen whales (Mysticeti) and the toothed whales (Odontoceti).

There are twelve species of baleen whales belonging to four families, and includes the largest of all animals on earth, the blue whale (Balaenoptera musculus). A new species, a small species similar to a fin whale (Balaenoptera physalus), was recognized in 2003 by Japanese scientists using molecular techniques. Baleen whales are characterized by having flexible horny plates with hairy fringes hanging from their upper jaws. The plates consist of a protein called keratin, which is the structural element of human hair. The whales take huge mouthfuls of water and use their tongues to squirt the water through the plates; they sieve out krill, plankton, and small fish. The whales undertake extensive migrations, moving into polar waters to exploit the rich populations of plankton that develop in the spring and summer. In winter they migrate into warm tropical seas to conserve energy and stop feeding. Calving tends to occur when they are in warm waters, so the newborn calves can use the energy from their mother's milk for growth rather than for keeping warm.

The toothed whales comprise ten families and include dolphins, beaked whales, the porpoise and the narwhal (Monodon monoceros), and the beluga (Delphinapterus leucas) or white whale. The male narwhal, which has one of its teeth developed into a long tusk, gave rise to the medieval myth of the unicorn. Belugas are also known as sea canaries, because of the loud chirping noises they produce when hunting under pack ice in the Arctic. The largest toothed whale is the sperm whale (Physeter macrocephalus), which feeds mainly on squid.

Whales are totally aquatic, although still dependent on the atmosphere for their oxygen. Their fusiform bodies are well insulated with fatty tissue known as blubber, which when rendered down was the source of the whale oil which created the whaling industry. They have tail flukes that are horizontal and beat vertically, and on the top of the head is the blowhole through which they inhale. They exhale or ‘blow’ before they dive or ‘sound’. Most dives last a few minutes, but the deeper-diving species, like the sperm whale and beaked whales (e.g. Ziphius spp.), can stay submerged for over an hour and can reach depths well in excess of 1,000 metres (3,000 ft). All species are highly vocal, using sound both to communicate between themselves and as sonar to detect their prey.

Whale populations are still threatened by whaling, but the biggest current threat is the use of powerful sonars by navies which are thought to disorient the whales' own sonar system. There have been several mass strandings of whales since the 1980s, which have coincided with NATO naval exercises. In 2002 fourteen beaked whales stranded themselves just four hours after new powerful sonars were switched on by warships exercising in the vicinity. Another potential threat is increases in the occurrences of red tides of the toxic algae (Alexandrium fundyense) which produces a poison, saxitoxin.

Bibliography

Evans, P. , The Natural History of Whales and Dolphins (1987).
Perrin, W.,, Wirsig, B.,, and and Thewissen, J. , Encyclopaedia of Marine Mammals (2002).

M. V. Angel

Cetacea (whales; infraclass Eutheria, cohort Mutica) An order that comprises the one extinct (Archaeoceti) and two extant (Odontoceti and Mysticeti) suborders of whales. The earliest whales (Archaeoceti) are known from Eocene rocks in Africa and South Asia (see BASILOSAURUS; AMBULOCETUS), and are descended from early Artiodactyla, probably more closely related to hippopotamus (Hippopotamidae) than to other groups. Of the two existing groups of whales, the Odontoceti (toothed whales) can be traced back to ancestral forms in the Upper Eocene, while the first definitive Mysticeti (baleen whales) occur in Oligocene strata. Whales are, streamlined, almost hairless, entirely aquatic. The fore limbs are modified to form paddles without visible digits, the hind limbs are absent, the pelvis is vestigial, except in some Archaeoceti. The tail fin is horizontal and used for propulsion. The skull is modified, with the nasal openings far back on the dorsal surface except in Physeteridae. The diet comprises fish and molluscs (Odontoceti) or mainly plankton (Mysticeti).

Cetacea An order of marine mammals comprising the whales, which includes what is probably the largest known animal – the blue whale (Balaenoptera musculus), over 30 m long and over 150 tonnes in weight. The forelimbs of whales are modified as short stabilizing flippers and the skin is very thin and almost hairless. A thick layer of blubber insulates the body against heat loss and is an important food store. Whales breathe through a dorsal blowhole, which is closed when the animal is submerged. The toothed whales (suborder Odontoceti), such as the dolphins and killer whale, are carnivorous; whalebone whales (suborder Mysticeti), such as the blue whale, feed on plankton filtered by whalebone plates.

whale Meat of Baleanoptera spp. A 150‐g portion is a rich source of protein, iron, and niacin; a source of vitamin B₂; contains 5 g of fat, of which 25% is saturated, 35% mono‐unsaturated; supplies 200  kcal (840 kJ).

whales See Cetacea.

whale See CETACEA.