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Dusky Dolphin
Size comparison against an average human
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Eutheria
Order: Cetacea
Suborder: Odontoceti
Family: Delphinidae
Genus: Lagenorhynchus
Species: L. obscurus
Binomial name
Lagenorhynchus obscurus
Gray, 1828
Dusky Dolphin range

The Dusky Dolphin (Lagenorhynchus obscurus) is a highly gregarious and acrobatic dolphin found in coastal waters in the Southern Hemisphere. It was first identified by John Edward Gray in 1828. It is very closely genetically related to the Pacific White-sided Dolphin, but current scientific consensus is that they are distinct species.

Contents

Taxonomy

Though the Dusky and Pacific White-sided Dolphins are traditionally placed in the genus Lagenorhynchus, recent molecular analyses indicate that they are more closely related to the dolphins of the genus Cephalorhynchus. If true, this would mean that these two species must either be transferred to Cephalorhynchus or be given a new genus of their own, as opposed to the current one that has been proposed for these species which is Sagmatias.[1]

Physical description

DuskyJump.jpg

The Dusky Dolphin is small to medium in length in comparison with other species in the family. There is significant variation in size among the different population areas. The largest Duskies have been encountered off Peru, where they are up to 210 cm (6 feet) in length and 100 kg (210 pounds) in mass. The back of the dolphin is dark grey or black and dorsal fin is distinctively two-toned—the leading edge matches the back in color, but the trailing edge is a much lighter greyish white. Duskies have a long, light grey patch on their foreside leading to a short, dark grey beak. The throat and belly are white. There are two blazes of white color running back on the body from the dorsal fin to the tail. Right between the white areas remains a characteristic thorn-shaped patch of dark colour, by which the species can easily be recognized. Aside from that, Dusky Dolphins may be confused with other members of their genus when observed at sea.

Population and distribution

The population of Dusky Dolphins is unknown, but authorities do not fear for the survival of the species at the moment. The Dusky Dolphin is distributed in coastal waters of Chile, Argentina and the Malvinas Islands, Namibia and the west coast of South Africa and all around New Zealand. There may also be resident populations off Tasmania and New South Wales and several small islands in the South Atlantic and Indian Oceans. An aerial survey off Patagonia in the mid-1990s indicated that there was a local population in excess of 7,000 individuals. Duskies can move over great distances (one individual had a confirmed range of 780 nautical miles) (1,440 km). However it is not believed that they follow a migatory pattern.

Pictures

References

  • Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K., Karczmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y., Wells, R.S. & Wilson, B. (2008). Lagenorhynchus obscurus. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 06 March 2009. Database entry includes a lengthy justification of why this species is listed as data deficient
  • National Audubon Society: Guide to Marine Mammals of the World ISBN 0-375-41141-0
  • Encyclopedia of Marine Mammals ISBN 0-12-551340-2
  • LeDuc, R.G., Perrin, W.F., Dizon, A.E. (1999). Phylogenetic relationships among the delphinid cetaceans based on full cytochrome b sequences. Marine Mammal Science 15, 619–648.
  • May-Collado, L., Agnarsson, I. (2006). Cytochrome b and Bayesian inference of whale phylogeny. Molecular Phylogenetics and Evolution 38, 344-354.
  1. ^ Shirihai, H. and Jarrett, B. (2006). Whales, Dolphins and Other Marine Mammals of the World.. Princeton Field Guides. p. 209–211. ISBN 0-61-12757-2.  

External links

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