Dusky dolphin

Lagenorhynchus obscurus
Other names: 
  • Fitzroy's dolphin
Maximum length: 
  • Male: 2.1m
  • Female: 2m
  • Calf: 0.8m
Maximum weight: 
  • Male: 85 kg
  • Female: Unknown
  • Calf: Unknown
Diet: 
  • Fish (including southern anchovy, hake and lanternfish)
  • Squid
Estimated population: 
Unknown
IUCN Listing: 
DD
CITES Appendix: 
II
CMS Appendix: 
II
Classification: 

The dusky dolphin was the subject of one of the first ever photo-identification studies, carried out off of Patagonia, Argentina. At the same time, in Peru, dusky dolphins were being targeted in multi-species cetacean fisheries. Thousands of individuals are estimated to have been caught (10,000 in 1985 alone) and the population has been seriously depleted over the past decades. Although now banned by law, the hunts are thought to continue on a much reduced scale. Currently three sub-species are recognised; L. o. fitzroyi - Fitzroy's dusky dolphin, L. o. posidonia - Peruvian and Chilean dusky dolphin, and L.o.un-named subsp. - NZ dusky dolphin.

Appearance: 

The dusky dolphin is a medium-sized, sturdy animal with a tall, falcate dorsal fin. The flippers are long and pointed with a curved leading edge, and the flukes have a notch in the middle with concave trailing edges. The back is dark grey to bluish-black. The dorsal fin is two toned, the leading edge matching the back while it fades to a lighter grey on the trailing edge. The dark melon slopes into a pale face and blunt, short, dark beak. There is a two-pronged white blaze from the tailstock to under the dorsal fin, and a grey thoracic patch from the face along the lower sides. The flippers are also dark, and the throat and belly are white. They resemble Pacific white-sided dolphins although their range doesn't overlap and they can sometimes be confused with Peale's dolphins, but they do not have the distinctive black ‘mask' of that species.

Behaviour: 

Dusky dolphins are fast, active swimmers. They are one of the most acrobatic of all the dolphins and perform amazingly high jumps, flips, and twists. When one dolphin starts leaping, the rest of the group often follow. Dusky dolphins are highly inquisitive towards boats and can be easy to approach. They are very social and can be found in groups of hundreds of individuals. This, combined with their acrobatic behaviour, makes the species very popular with dolphin-watching enthusiasts. They are frequently seen with other cetaceans as well as with seabirds. Individual dusky dolphins have been shown to cover vast distances, but they are not thought to be migratory. They are known to feed both during the day and at night and feed on anchovies at the surface as well as squid, hake, and lanternfish.

Distribution: 

Dusky dolphins are found mainly in coastal waters, or over the continental shelf and research has shown there are three subspecies; (1) L. o. obscurus - Namibia and South Africa, (2) L.o. fitzroyi – southern South America, and (3) an as yet unnamed subspecies found off of New Zealand, Australia and several oceanic islands in the Indian Ocean. Genetic evidence suggests that sub-populations exist within these subspecies, which is important for management purposes. There is a big variation in body size between these different populations - the largest dusky dolphins being found off Peru. The main threats to dusky dolphin populations are targeted hunts and entanglement in fishing nets. It is not known how many dusky dolphins there are worldwide and they are officially listed by IUCN as Data Deficient.

Distribution map: