HSVISIDE'S DOLPHINS

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

 

 Name

Haviside's dolphin, whose binomial name references heavisidii, 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 misspelled 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 literature. Some authorities, including the Encyclopedia of Marine Mammals and Mammal Species of the World use the originally intended name of Haviside's dolphin.

Population and distribution

 

 Although sightings of the species are not uncommon off the Skeleton Coast of Namibia, Haviside'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. Sightings are likely from Lambert's Bay either from the shore or from boat trips run from the harbour. No estimates of abundance exist.

Physical description

Haviside's dolphins off Walvis Bay, Namibia

Haviside's dolphin is a fairly small dolphin, growing to about 1.8 m (5 ft 11 in) in length and weighing up to 75 kg. Their size and the bluntness of their heads lead 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.^[2] The dorsal fin, fluke and back half of the back are again a darker grey colour. The underbelly is white, with flashes of white on the flanks below the dorsal fin.
Males reach sexual maturity at about seven to 9 years. Females reach breeding age at the same time. The gestation period is probably 10 months. Mating occurs in spring and summer. Females are believed to calve on average once every three years. The maximum known age of a Haviside's dolphin is 20 years. This relatively short lifespan, coupled with the long calving period, causes a naturally low population growth rate. Therefore, the species is particularly sensitive to being hunted.
Haviside's dolphins are active and social animals. They typically congregate in groups of about five to 10 in number, but sometimes in larger groups. They are able to swim fast. Part of their play and social activity is to jump vertically clear of the water, turn in the air, and fall back into the sea with virtually no splashing or noise.

 

 

 

 

Conservation

Heaviside's dolphin is listed on Appendix II^[3] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II^[3] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.^[4] Heaviside's dolphin is covered by the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia.^[5]