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Chilean Dolphin

From Academic Kids

Chilean Dolphin
Conservation status: Unknown
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Mammalia
Subclass:Eutheria
Order:Cetacea
Suborder:Odontoceti
Genus:Cephalorhynchus
Species:C. eutropia
Binomial name
Cephalorhynchus eutropia
Chilean Dolphin range
Chilean Dolphin range

The Chilean Dolphin (Cephalorhynchus eutropia), also known as the Black Dolphin (although this name has fallen out of favour in scientific circles), is one of four dolphins in the Cephalorhynchus genus. The dolphin is only found off the coast of Chile.

Contents

Physical description

The Chilean Dolphin is a small dolphin at around 170 cm in length, with a blunt head. These characteristics often make for incorrect identification as a porpoise. The Dolphin is thickly-shaped with its girth up to two-thirds its length. The dorsal fin and flippers are small in proportion to body size in comparison with other dolphins. The throat, underside and the closest part of the flippers to the body are white. The remainder of the body is a mix of greys. The Dolphin has 28-34 pairs of teeth in the upper jaw and 29-33 in the lower.

The Dolphin is normally sighted in small groups of around two to ten individuals, with some larger gatherings occasionally sighted.

Longevity, gestation and lactation periods are not known, but are believed to be similar in length to the more studied, and similar, Hector's and Commerson's Dolphins which have a gestation period of about ten months to one year and maximum longevity of twenty years.

Population and distribution

The population of the Chilean Dolphin, perhaps one of the least studied of all cetaceans, is not known with certainty. There may be as many as a few thousand individuals, although at least one researcher, Steve Leatherwood, has suggested that the population may be much lower (see also [1] (http://www.unep-wcmc.org/cms/pdf/Rpt_Schlatter.PDF) for a survey of South American cetacean population with data on the Chilean Dolphin). Whatever its number, the Chilean Dolphin is endemic to the coast of Chile and thought not to migrate. The dolphin is seen over a wider interval of latitudes than other Cephalorhynchus species - from Valparaíso at 33° S to Cape Horn at 55° S. The species appears to prefer areas of shallow water (less than 200 m depth) and in particular enjoys fast-flowing tidal areas and mouths of rivers.

Name

In the early part of the twentieth century the Chilean Dolphin was commonly known as the Black Dolphin. This was later agreed to be a poor choice of name. Most of the few individual specimens studied by scientists were either washed-up individuals whose skin had darkened due to exposure to air or live specimens seen at sea but only at a distance (and so appeared darker than they were). As more specimens were studied it became clear that the back of the dolphin was in fact a mixture of grey colours and that its underside was white. The scientific community are now universally agreed in naming the dolphin Chilean on account of its distribution along the coast of the country.

Conservation and whaling

The Chilean Dolphin is the only Cephalorhynchus not to readily ride the bow-waves of boats. This is believed to be due to wide-spread hunting by harpoon of the dolphins that occurred up until the early 1980s, causing individuals to become wary of boats. Up until hunting was banned around 1,300-1,500 individuals a year were killed. Nowadays a few individuals are lost each year in fishing equipment. It is possible, given the possible precariousness of the population, that these losses are causing an irreversible decline of the species, but this is not known with certainty.

References

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