Tursiops truncatus
The Bottlenose Dolphin, Tursiops truncatus is a highly variable species with at least two recognisable forms, inshore and off shore. This is the classic dolphin of film and oceanarium fame and is probably the marine mammal most people recognise. It has a short rounded snout, described as bottle-shaped, a smooth rounded melon and an overall body length that varies from 1.9m to 4m. The large dorsal fin is slightly hooked and set half way along the body. Overall the body colour is a series of grey tones with an indistinct paler grey wash on the flanks fading into an off-white belly.
The Bottlenose Dolphin occurs in all oceans and seas. They are resident or frequent inhabitants of bays and coastal areas. In some areas populations will maintain defined home ranges within recognised coastal landforms. Others are pelagic animals, found well out to sea, often off or quite close to a continental shelf edge. This species occupies a broader range of habitats than any other marine mammal.
This is still an abundant species despite incidental kills by the fishing industry. However, habitat degradation and pollution are of increasing concern for Bottlenose Dolphins. Pollution is thought to have resulted in some cases of mass die-offs which occurred off the coast of the United States of America and in the Gulf of Mexico.
The wide range of habitats this species occupy gives it access to a huge variety of organisms including invertebrates, bottom-dwelling fish and squid plus the full range of pelagic fish species. Bottlenose Dolphins are a very social species and feed together, although they are known to feed alone. They also take advantage of human-induced prey abundance and regularly approach fishing trawlers.
This species life history is well known from years of observation in the wild and from its long history as a captive animal. The social organisation of groups and their size varies greatly, to some extent depending on the habitat. Animals in bays form only small groups of maybe 15 individuals while those off shore may number in the hundreds. Birth of the young occurs after a gestation period of about a year. A single calf is born and suckled for about 12 to 18 months. It may then continue to associate with the female for a number of years. They are a long-lived species with an extensive life span of up to 45 years.
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Copyright © Australian Museum, 2003
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