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Dolphins are fishlike in form, with streamlined, hairless bodies. Their powerful, horizontal flukes, or tail fins, drive them through or out of the water, while their forefins and dorsal fin are used for steering. Constantly shedding their skins, dolphins accumulate no barnacles or other external parasites. A layer of blubber protects them from cold and seals small wounds. Dolphins breathe air through a single, dorsal blowhole.
The dolphin's intelligence, playfulness, and friendliness, its built-in smile and merry-looking eyes have been a source of interest and enchantment to human beings from earliest times; it is a common figure in mythology and literature and has been much depicted in art, especially in the posture of its graceful, arched, 30-ft (9-m) leap. Dolphins have long been famous for riding the bows of ships, and it is now known that they also ride the bows of large whales. Today they are valued and exploited as entertainers in more than 40 water shows around the world and have thus become available for extensive study.
The best known species are the common dolphin (Delphinus delphis), of worldwide distribution, and the bottle-nosed dolphin (Tursiops truncatus), found in coastal waters of the North Atlantic Ocean and the Mediterranean Sea. The bottlenose has been particularly intensively studied; it is presumed that much of what is known about this species applies to other dolphins and even to the large whales.
Common Dolphin
The common dolphin averages 8 ft (2.4 m) in length and 165 lb (75 kg) in weight. It has a dark blue or black upper body, a white underbody, golden stripes on the sides, and a sickle-shaped dorsal fin. Its pronounced, slim beak, holding 100 teeth, is separated from its snout by a deep groove. A fast swimmer, it travels in large schools in warm waters and is noted for leaping alongside boats for long distances. Its life span is about 50 years.
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