Dolphin

Dolphin is a common name of aquatic mammals within the infraorder Cetacea. The term dolphin usually refers to the extant families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), and Pontoporiidae (the brackish dolphins), and the extinct Lipotidae (baiji or Chinese river dolphin). There are 40 extant species named as dolphins.

Anatomy

Dolphins have a streamlined fusiform body, adapted for fast swimming. The tail fin, called the fluke, is used for propulsion, while the pectoral fins together with the entire tail section provide directional control. The dorsal fin, in those species that have one, provides stability while swimming.

Behavior

Dolphins are well known for their agility and playful behavior, making them very popular in human culture. They are capable of making a broad range of sounds using nasal airsacs located just below the blowhole. Roughly three categories of sounds can be identified: frequency modulated whistles, burst-pulsed sounds and clicks.

Conservation

Many species of dolphins are threatened by human activities. Dolphins occasionally feature in literature and film, as in the film series Free Willy. Dolphins are sometimes kept in captivity and trained to perform tricks. The most common dolphin species in captivity is the bottlenose dolphin, while there are around 60 captive killer whales.

See also

• Whale
• Porpoise
• Cetacean Intelligence
• Cetacean Conservation

References

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