Description
The dusky dolphin is small to medium in length compared with other species in the family. There is significant variation in size among the different population areas. The largest dusky dolphins have been encountered off the coast of Peru, where they are up to 210 cm (6 feet) in length and 100 kg (210 pounds) in mass. The size for dusky dolphins in New Zealand have been recorded to be a length range of 167–178 cm and a weight range of 69–78 kg for females and a length range of 165–175 cm and a weigh range of 70–85 kg for males.
There is almost no sexual dimorphism in this species, although males have more curved dorsal fins with broader bases and greater surface areas. The back of the dolphin is dark grey or black, and the dorsal fin is distinctively two-toned—the leading edge matches the back in color, but the trailing edge is a much lighter greyish white. Dusky dolphins have a long, light grey patch on their foreside leading to a short, dark grey beak. The throat and belly are white, and the beak and lower jaw are dark grey. 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. It can be distinguished from the common dolphins, which have a more prominent and longer beak and yellow flank markings. The skull of a dusky dolphin has a longer and narrower rostrum than that of a hourglass dolphin or Peale's dolphin of similar age and size.
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