Espolarte - Marine mammals - Bottlenose Dolphin

Bottlenose Dolphin

Common Bottlenose Dolphin (Tursiops truncatus)

Indo-Pacific Bottlenose Dolphin (Tursiops aduncus)


Bottlenose Dolphins. Photo: Isabel Guzmán

The Bottlenose Dolphin, frequently exhibited in dolphinaria, is probably the cetacean best known by non-professionals. The term bottlenose dolphin actually comprises two dolphin species, Tursiops truncatus and Tursiops aduncus. Both are toothed whales, and members of the oceanic dolphin family (Delphinidae).

Description

The Bottlenose Dolphin is a small cetacean, but fairly large for a dolphin. Length 3 m, max. 4,2 m; calves about 1 m at birth. Weight averages 200 kg, with greatest weight recorded 650 kg; calves weigh about 32 kg at birth. Body is robust but streamlined, beak short and rounded, mouth has a slight smiling expression. Dorsal fin is large and curves backwards. Skin is greyish, back is darker than belly. There are 24 to 25 teeth on each side of each jaw. Tursiops aduncus is slightly smaller than Tursiops truncatus and has a brownish colouration.


Bottlenose Dolphin as represented in a Czech field guide

Identification

Bottlenose Dolphin, unafraid of man, is easy to approach. It seldom shows its head, usually only its arched back and fin can be seen. When near surface, breathes 2 or 3 times each minute; rarely dives for more than one minute. Breaching is fairly rare. May be confused with Stenella species and the roughtooth dolphin (Steno bredanensis).

Natural history

Feeds mainly on inshore bottom-dwelling fish, but also eats pelagic fish, rays, small sharks, crabs and shrimps. Lives in groups of 1015 animals, but "schools" of 1000 animals were also recorded. Calves are born in spring or summer and are lactated for a year. The bottlenose dolphin is highly intelligent, and has a sophisticated echolocation system. However, solitary and group strandings are rather common.


Photo: Isabel Guzmán

Distribution

Occurs worldwide in warm and temperate seas. Prefers shallow inshore waters, may enter estuaries and rivers, but may also be found hundreds of kilometres from nearest coast. Tursiops aduncus lives along the coasts of India, Southeast Asia, southern China, Indonesia and Australia.

Status and threats

Both species are common, but some local populations are threatened by hunting, pollution and habitat destruction. Capturing live animals for display also has negative effects on some populations.