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. 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.

(From Wikipedia.org, September 13 2010)

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The dusky dolphin is a highly social species, sometimes found in herds of over 1,000 individuals, although groups of 20 to 500 are more common (3). Large groups often come together to cooperatively hunt prey, which is quite varied and includes anchovy, squid and shrimp. The species may also feed at night. The dusky dolphin frequently associates with other cetaceans (2) (3) (6), and is said to be one of the most acrobatic of all dolphins, readily approaching boats to bow-ride, and often leaping high out of the water and tumbling in the air (3). Mating is believed to occur in spring, with a single calf born after a gestation period of 11 months (6) and measuring around 55 to 70 centimetres at birth (3) (6). Births usually peak in summer (November to February) around New Zealand and Argentina, and in winter (August to October) around Peru (2). Calves are weaned at around 18 months (6).

(From ARKives via The Encyclopedia of Life, September 13 2010)

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Dolphins begin at 0:55.