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Dusky Dolphin

(Lagenorhynchus obsurus)

Short Description

The Dusky Dolphin is small and chunky, with a backward curving dorsal fin that is large for its body, high and pointed. It has a short, thick beak. Known as the ‘Tourist Friendly’ dolphin, the dusky readily approaches vessels at sea, participating in active bow-riding and leaping and somersaulting around the vessel to entertain the passengers.

Long Description

Size
Dusky dolphins are medium to small, growing to only 2 metres in length and weighing 90 kg or less. 

Identification
Its colouration is complex and distinctive, with the jaw, back, dorsal fin, flukes and flippers being black.The belly, sides and face are pale and whitish with an irregular shaped whitish area below and behind each side of the dorsal fin and again on each side of the tail base. It is well known for its accomplished aerial acrobatics.

Diet
The dusky dolphin has between 24 and 36 pairs of simple, conical teeth in each jaw. Its diet comprises of fish and squid which it hunts in early morning and late afternoon. They sometimes feed in large schools.

Social Groups and Activity
It is a tourist friendly species which readily rides bow-waves, leaps clear of the water and even completes full forward somersaults ending in a belly flop back into the water.

Marine mammal scientists Bernd and Melany Wursig, who studied dusky dolphins for several years in the waters off Patagonia, identified at least three types of acrobatic behaviour which could serve a specific function. The first is a "head-first re-entry leap" which doesn't make much of a splash. The Wursigs believe that the dolphin may be taking this opportunity to look for feeding sea birds which may indicate the location of shoaling anchovies. The second is a "noisy leap" where the dolphin lands on the surface of the water on its back or side, but only once fish have been located. This may serve to signal the location of fish to other dolphins, or to confuse and frighten the anchovies. The third is a leap, which appears to have no apparent explanation. It is an exuberant display of twisting, turning and somersaulting which is seen most often after feeding. The Wursigs account for it as "pure joy".

Reproduction
Very little is known about the biology of the dusky dolphin population which is found regularly along the South African coast, but in New Zealand, the birthing and mating appear to occur primarily in summer.

Distribution

The Dusky Dolphin is found in the cold waters of the Benguela Current on the west coast of Africa as far north as Angola, but does not extend farther east than False Bay on the southern coast of South Africa, not passing from Atlantic to Indian Oceans. Large groups of several hundred individuals have been observed in False Bay, although groups of 20 animals are more common. It occurs in shallow inshore waters, in bays and in the deeper waters beyond the edge of the continental shelf. It appears that the dusky dolphin remains in deeper water at night and comes inshore during the day to possibly rest and/or avoid predators.

Distribution Map

Dusky Dolphin  Distribution Map

Various

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