dolphin

dolphin,

aquatic mammal, any of the small toothed whales of the family Delphinidae, numbering more than 50 species. These include the true, or beaked, dolphins, the killer whale, the pilot whale, and the freshwater species found in rivers of South America and S and E Asia. Most species are highly gregarious. The name dolphin, meaning "beaked," is also applied to a species of fish (see dolphin, fish). In the United States dolphins are often mistakenly called porpoises, a name correctly applied to small, blunt-nosed whales of another family. Until recently dolphins formed the basis of a widespread fishing industry; only the Japanese continue to hunt them for food on a large scale. They are accidentally caught and killed in large numbers in tuna seining operations.

Characteristics and Species

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.

Bottle-nosed Dolphin

The bottle-nosed dolphin is blue-gray with a dorsal fin and white belly. Its average length is 9 ft (2.7 m) and its average weight 350 lb (160 kg). Its domed forehead, called the melon, contains an oily substance thought to protect the brain case and to act as an acoustic lens. With age the 200 or more teeth of the bottlenose wear down, hence the name truncatus. Members of this species live about 25 years. Bottle-nosed dolphins swim in large schools with a social organization and hierarchy, hunting the small fish, crustaceans, squid, and cuttlefish that make up their diet. They have been clocked swimming at 30 mi (48 km) per hour, although 20 to 24 mi (32–39 km) per hour is their usual speed. They can dive 70 ft (20 m) and remain underwater for 15 minutes. They sleep by night, just below the surface of the water, rising for air every three or four minutes.

Their aquatic natural enemies are sharks and killer whales; these they attempt to outswim, using complex evasive strategy, or batter to death, acting in a group. If one of their number is injured or sick they make every effort to rescue it, holding it above the water for air. Play behavior is highly developed in the bottlenose from infancy through old age, and in this connection it displays considerable tool-making, tool-using, and manipulative ability; for example, a dolphin has been observed to kill a fish, strip its skeleton, and use the bones, held in the mouth, to pry another fish out of a crevice. Sex play is frequent and is initiated by any individual toward any other, without regard to size, age, sex, relationship, or even species; approaches to human beings and to turtles are common.

Courtship and impregnation occur mainly in spring, when males vie for the attention of the females. A single calf, 3 1-2 ft (97 cm) long and weighing 30 lb (14 kg), is born tail first after a gestation of 12 months. The mother or a female assistant bites the umbilical cord in two and pushes the calf to the surface to breathe; it is nursed for one to two years. One female may watch over several calves while the mothers hunt, or during battle.

The senses of the bottlenose have been subjected to intensive investigation, as have their intelligence and their remarkable systems of echolocation and communication. In relation to body size, the brain of the adult bottlenose is comparable in size to that of humans; it is twice as convoluted and possesses 1 1-2 times as many cells. The bottlenose has partially stereoscopic vision that is keen both in water and in air; when the animal leaps from one medium to the other, its brain corrects for the difference in refractive index. The eye has a glowing layer for night vision and a brownish filter that is lowered over the iris in bright sunlight. The brain has no olfactory lobe and the sense of smell is presumably missing, but the taste buds are well developed and are used to detect underwater chemical traces, as when the dolphin tracks fish.

Echolocation and Communication

Dolphins produce an enormous variety of sounds, up to frequencies ten times those heard by human beings. The sounds are apparently produced by a complex of anatomical structures including the blowhole with its air sacs and valves. Each dolphin has a signature whistle with which it identifies itself; a calf soon learns to recognize its mother's whistle. Clicking and rapid creaking sounds are the basis of the echolocation mechanism (sonar) with which the dolphin gathers extremely precise information about the size, location, and nature of surrounding objects. Dolphins communicate by means of a demonstrably descriptive language understood by more than one species, using all the sounds in their repertory. They are observed to converse, and it has been repeatedly shown that one animal can convey instructions to another. Computer-aided efforts are being made, so far without success, to learn the dolphin language and to teach dolphins human speech, either in its normal form or translated into whistle combinations.

Interaction with Humans

Dolphins are capable of imitation and memorization; they demonstrate foresight, learn from observation, communicate experience, solve complex problems, perform elaborate tasks, and learn multiple procedures simultaneously. Their so-called training is in fact a discipline structured around play, using their natural behavior as the basis for involved maneuvers; they appear to perform primarily for their own enjoyment. In situations of great stress in captivity they have been known to commit suicide by starvation, battering against walls, or drowning. There are many reports of dolphins rescuing people from drowning.

The United States and Russian/Soviet navies have spent vast sums to reach a greater understanding of dolphin echolocation, which could have countless military applications. The U.S. navy has trained dolphins to act as messengers to underwater stations, to rescue wounded scuba divers and protect them from sharks, to locate and mark underwater mines, and to seek and destroy submarines, using kamikaze methods; this last project met with considerable public criticism.

Classification

Dolphins are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Cetacea, family Delphinidae.

Bibliography

See W. N. Kellogg, Porpoises and Sonar (1961); K. S. Norris, ed., Whales, Dolphins and Porpoises (1966); E. Devine and M. Clark, The Dolphin Smile (1967); R. Stenuit, The Dolphin, Cousin to Man (1968); D. K. and M. C. Caldwell, The World of the Bottlenosed Dolphin (1972); M. M. Bryden and R. Harrison, ed., Research on Dolphins (1986); R. Ellis, Dolphins and Porpoises (1989); H. Whitehead and L. Rendell, The Cultural Lives of Whales and Dolphins (2014).

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dolphin,

large, swift game fish, Coryphaena hippurus, also called dorado. It is of nearly worldwide distribution in warm waters. Its long, slender body is blue, and in the living animal there are luminous shades of gold, green, and purple. The dolphin has a dorsal fin that runs the length of the body and a forked tail. Males, larger than females, may reach a length of nearly 6 ft (1.8 m) and a weight of over 65 lb (30 kg). Dolphins travel alone or in groups, attaining speeds of 35 mi (56 km) per hr. They feed on a variety of fishes, especially flying fish, which they sometimes pursue by leaping out of the water. They are valued as food in Polynesia, where they are known as mahimahi. The term dolphin is also applied to a group of aquatic mammals (see dolphin, mammal). The fish known as dolphins are classified in the phylum Chordata, subphylum Vertebrata, class Actinopterygii, order Perciformes, family Coryphaenidae.

Dolphin

(religion, spiritualism, and occult)

The dolphin is a traditional alternate name for the sign Pisces.

Dolphin

 

freestanding supports that take up the loads when vessels dock and fall foul. There are mooring dolphins, breasting dolphins, swinging dolphins, and guiding types. They may be rigid, with a slight lateral yield, or flexible. The dolphins are installed directly in front of berths that are not designed to withstand horizontal loads and in front of sloping structures to prevent vessels from falling foul of the shore. They are also placed in roadsteads for the benefit of vessels unloading or waiting to unload. Dolphins placed at approaches to berths or at the entrance to a lock or harbor help vessels to hold the correct position, and dolphins of the floating type serve to hold vessels off from mooring structures.

REFERENCES

Goriunov, B. F., and F. M. Shikhiev. Morskie porty i portovye sooruzheniia. Moscow, 1970.
Mikhailov, A. V. Vnutrennie vodnye puti. Moscow, 1973.

What does it mean when you dream about a dolphin? (porpoise)

Large bodies of water often symbolize the unconscious, so any sea creature can represent a message from the unconscious or diving into the unconscious. As seagoing mammals, dolphins can symbolize the connection or interaction between our conscious (air) and unconscious (water) selves, or between thoughts (air) and emotions (water). They also represent guides to the unconscious. Because of our society’s general knowledge about dolphin behavior, they also symbolize rescuers.

dolphin

[′däl·fən]

(civil engineering)

A group of piles driven close and tied together to provide a fixed mooring in the open sea or a guide for ships coming into a narrow harbor entrance.

A mooring post on a wharf.

(vertebrate zoology)

The common name for about 33 species of cetacean mammals included in the family Delphinidae and characterized by the pronounced beak-shaped mouth.

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Dolphin

[′däl·fən]

(astronomy)

Delphinus

dolphin

transported blessed souls to islands of dead. [Gk. and Rom. Myth.: Appleton, 31]

See: Guide

dolphin

1. any of various marine cetacean mammals of the family Delphinidae, esp Delphinus delphis, that are typically smaller than whales and larger than porpoises and have a beaklike snout

2. river dolphin any freshwater cetacean of the family Platanistidae, inhabiting rivers of North and South America and S Asia. They are smaller than marine dolphins and have a longer narrower snout

3. either of two large marine percoid fishes, Coryphaena hippurus or C. equisetis, that resemble the cetacean dolphins and have an iridescent coloration

4. Nautical a post or buoy for mooring a vessel

Dolphin

(dreams)

Dolphins represent friendliness, communal living, rescue, communication, and affection. They are water dwelling mammals and in our dreams they represent our willingness and ability to navigate through emotions. They represent positive messages from our unconscious minds. Dolphins could also represent a positive connection between our consciousness and to those parts of the psyche that are a mystery and largely unconscious.