Dusky Dolphins are a small, moderately robust species with a short rostrum (snout) clearly demarcated from the melon (forehead). The conspicuous dorsal fin is moderately falcate (sickle-shaped) and pointed. Flippers are moderately curved on the leading edge, with a blunt tip. Dusky Dolphins can live for more than 21 years and reach a maximum length of 2.11 m for males, and 1.93 m for females. The body colouration of Dusky Dolphins is complex and is generally counter-shaded, dark grey to black above and white below. The sides are marked with blazes and patches of pale grey. In front of the dorsal fin, Dusky Dolphins bear a broad light grey thoracic patch that encompasses the face, most of the head and flanks, and then tapers towards the belly. A separate crescent-shaped flank patch reaches the top of the tail stock just in front of the flukes. The front of this flank patch splits into two blazes, a shorter ventral and a longer dorsal one. The longer dorsal blaze narrows and stretches up onto the back, almost to the blowhole. The rostrum (snout) is grey-black around the tip, tapering back to darken the lips near the gape. The eye is set in a small patch of grey-black. A variable crescent of pale grey contrasts the trailing (backward-facing) half of the dorsal fin with the dark coloured front half. The flippers are pale grey but darken around the edges. Dusky Dolphins occur in groups of hundreds of individuals in summer and less than 20 in winter. In some cases, large schools of several hundred dolphins have been observed. Dusky Dolphins tend to rest in shallow water. This species readily rides the bow-wave of vessels and indulges in spectacular aerial displays including full somersaults high in the air. Most aerial behaviour is associated with surface feeding, while the more acrobatic displays are associated with social behaviour. Dusky Dolphins are known to dive to at least 150 m depth.
Dusky Dolphin |
Government evidence of impact of climate change:
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Australian Government Department of Agriculture, Water and the Environment, Species Profile and Threats Database, Lagenorhynchus obscurus
No past declines in extent of occurrence are known; although increasing ocean temperatures predicted by climate change scenarios could potentially decrease the extent of occurrence; with warmer water extending southwards beyond 35 S.