WHALE

any of several species of exclusively aquatic mammals who, along with the porpoises and dolphins, constitute the order Cetacea (see cetacean). The term whale is sometimes used interchangeably with cetacean, but more often whales are distinguished from the usually smaller porpoises and dolphins and also sometimes from narwhals. Humpback whale (Megaptera novaeangliae) breaching. Whales (and cetaceans generally) are divided into three suborders: (1) Archaeoceti, which are extinct heterodont- (differentiated-) toothed cetaceans, (2) Mysticeti, which are baleen, or whalebone, whales and include the gray, right, rorqual, humpback (see photograph), and blue whales, and (3) Odontoceti, which are homodont- (uniform-) toothed cetaceans and include the sperm, bottle-nosed, beaked, killer, beluga, and pilot whales (as well as dolphins, porpoises, and narwhals). The mysticetous whales have whalebone, or baleens, instead of teeth. The baleen is a dense fringe of blade-shaped, horny plates that hangs down from the roof of the mouth. Baleen whales feed on plankton, on small crustaceans such as krill, and on other tiny sea life. They feed either by swimming with their mouths open or by gulping water. The fringe of the baleen acts as a strainer to the relatively small throat, letting water out but holding back the food. The odontocetous, or homodont-toothed, whales, on the other hand, have slicing teeth and throats large enough to swallow chunks of giant squid, cuttlefish, and fish of all kinds. Humpback whale surfacing, showing blowholes. Some whales are larger than the largest ancient dinosaurs; a blue whale (Balaenoptera musculus) may be up to 33.6 m (110 feet) long and weigh more than 136,000 kg (150 tons). Whales are warm-blooded animals with skeletal, vascular, alimentary, respiratory, sensory, and reproductive features fundamentally the same as those in other mammals despite their superficial general resemblance to the fishes. They must come to the water's surface to breathe through blowholes located on top of their heads (see photograph). When washed ashore, they are helpless; without the support of water they cannot move, and their lungs may be crushed by the weight of the body. Whales have exploited all the available aquatic habitatsthe oceans and the seas connected with them, as well as estuaries and rivers. They are especially numerous in the Antarctic Ocean, which is rich in plankton and other marine life. Some whales are social, traveling in groups called schools, herds, pods, or gams. Whales produce two basic types of underwater sounds. The low-pitched signals, such as the barks, whistles, screams, and moans audible to humans, are used in social communication, while the brief clicks of high-intensity sound, usually inaudible to the unaided human ear, are used to navigate or to identify food sources. Whales yield several products of commercial valueincluding whale meat, whale oil (q.v.), whalebone, and ambergris (q.v.)around which grew the industry of whaling (q.v.). In the late 20th century, in an attempt to conserve whales, the International Whaling Commission (IWC) tried to limit the sizes, kinds, locations, and seasons of catches. In 1986 the IWC imposed a moratorium on commercial whaling, with only moderate success. In 1994 the IWC established a whale sanctuary, permanently banning whaling in the waters around Antarctica.