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Heaviside Dolphin


Heaviside's Dolphin (Cephalorhynchus heavisidii) is a small dolphin that is found off the coast of Namibia and the west coast of South Africa. It is one of four dolphins in the Cephalorhychus genus - the others being the Chilean Dolphin, Hector's Dolphin and Commerson's Dolphin.

Name:
Heaviside's Dolphin is actually named after a Captain Haviside who brought a specimen from Namibia to the United Kingdom early in the 19th Century. However its name was once mis-spelled Heaviside, after a prominent surgeon, Captain Heaviside who collected cetacean and other animal species. The latter name stuck and is the most common in the popular literature. However some authorities, including the Encyclopedia of Marine Mammals use the originally intended name - Haviside's Dolphin


Population and distribution:

Although sightings of the species are not uncommon off the Skeleton Coast of Namibia, Heaviside's Dolphins have not been systematically studied by scientists. They have been recorded off the coast of northern Namibia at 17° S and as far south as the southern tip of South Africa. Sightings are often recorded from major population centres such as Cape Town and towns such as Walvis Bay. No estimates of abundance exist.


Physical description:
Heaviside's Dolphin is a fairly small dolphin - growing up to about 180cm in length and weighing up to 75kg. Their size and bluntness of their head leads these dolphins to often be mistaken for porpoises. The head is coloured a dark grey. The front half of the upper side and the flanks are a much lighter grey. The dorsal fin, fluke and back half of the back are again a darker grey colour. The underbelly is white and there are flashes of white on the flanks below the dorsal fin.

Males reach sexual maturity at about 7-9 years. Females reach breeding age at the same time. The gestation period is probably 10 months. Mating occurs in Spring and Summer. It is believed that females calf on average once every three years. The maximum known age of a Heaviside's Dolphin is 20 years. This relatively short life span, coupled with the long calving period, causes a naturally low population growth rate. Therefore the species is particularly sensitive to being hunted.

Heaviside's Dolphins are active and social animals. They typical congregate in groups of about 5-10 in number, and sometimes in larger groups. They are able to swim fast. Part of the play and social activity is to jump vertically clear of the water, turn in the air, and fall back into the sea without virtually no splashing or noise.


References:

National Audubon Society: Guide to Marine Mammals of the World Reeves, Stewart, Clapham and Powell, (2002).

Encyclopedia of Marine Mammals: Article on Cephalorhynchus dolphins, p200-202, Stephen M. Dawson (1998).