Heaviside's dolphin

Heaviside's dolphin
File:Dolphins at Lüderitz, Namibia (3144863196).jpg
Heaviside's dolphin off Luderitz
File:Heaviside's dolphin size.svg
Size compared to an average human
Conservation status
Data Deficient (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Subclass:	Eutheria
Order:	Cetacea
Suborder:	Odontoceti
Genus:	Cephalorhynchus
Species:	C. heavisidii
Binomial name
Cephalorhynchus heavisidii Gray, 1828
File:Cetacea range map Heaviside's Dolphin.PNG
Heaviside's dolphin range

Heaviside's dolphin (Cephalorhynchus heavisidii), sometimes called Haviside's dolphin after its discoverer, 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

Early in the 19th century, a specimen was caught off the Cape of Good Hope and brought to the United Kingdom by a Captain Haviside of the British East India Company. Zoologist John Edward Gray, who described the species in his Spicilegia Zoologica, misidentified Haviside as a surgeon of note named Heaviside, whose collection was acquired roughly contemporaneously. "Heaviside's Dolphin" is most common in the literature, though some authorities 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. 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

File:Heaviside-Delphin.jpg

Heaviside's dolphins off Walvis Bay, Namibia

Heaviside'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. 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 Heaviside'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.

Heaviside'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 of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.

Heaviside's dolphin is covered by the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia.

See also

• List of whale and dolphin species

Further reading

• National Audubon Society: Guide to Marine Mammals of the World Reeves, Stewart, Clapham and Powell (2002)
• Cephalorhynchus dolphins, Encyclopedia of Marine Mammals, pp. 200–202, Stephen M. Dawson (1998) ISBN 0-12-551340-2