The genus comes from the Greek word lagenos for bottle or flask, and rhynchos meaning nose or snout; obscurus comes from a Latin word meaning 'dark, indistinct'.
Dusky dolphins have a complex body coloration pattern. Laterally, the body can be separated into four areas: spinal field, flank patch, thoracic patch and white abdominal field. The body is counter-shaded, with bluish black dorsal surface, snout and tail and a white belly and throat underneath. Blazes of gray run along the flanks.
Duskies have a short stubby beak, much different from the prominent beaks of the stenellid species. The tall and slightly hooked dorsal fin is darkly colored on the leading edge but fades to lighter gray towards the trailing edge. Flippers are pale gray in front but darken in color along the trailing edge.
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 Falkland Islands, Namibia and the west coast of South Africa and the east coast of 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 ariel survey over Patagonia in the mid-1990s indicated that there was a local population in excess of 7,000 individuals. Duskys can move over great distances (one individual had a confirmed range of 780kn). However it is not believed that they follow a migatory pattern.
The body shape is small and moderately chunky. Maximum reported length for African specimens is 1.93 m for females and 1.81 m for males. Adult weights range from 40 to 80 kg, though birth weight is not known for the African population. Reported birth length ranges from 55 to 70 cm in other areas. African specimens tend to be larger than specimens from New Zealand, but smaller than those from Peru. The largest measured female from New Zealand is 1.78 m in length while the largest female specimen from Peru is 1.93 m. Males are slightly smaller, but heavier.
The location in Africa:
In Africa, duskies are only found on the west coast, from South Africa north to Angola. This meso-pelagic species can be found in coastal or continental shelf areas associated with cool currents of the Southern Hemisphere. Other disjunct populations of duskies can be found around New Zealand, both the east and west coasts of South America, especially off Peru and Argentina, and around several oceanic islands including Tristan de Cunha and Amsterdam Islands.
Conservation and dolphin-watching: Outside Peruvian coastal waters, the main danger to Dusky Dolphins from humans is the accidental catching of inidividuals by fishing trawls. In the mid-1980s around 400-600 animals were killed annually off Patagonia due to individuals becoming trapped in nets. Rates appear to have declined since then due to tighter regulations on the fishing industry. However in Peruvian waters in addition to accidental catches there is continuing deliberate catching via nets and harpoons. The number of animals killed each year in this area runs into the thousands and a conservationists' cause for concern.
On account of their highly acrobatic displays and movements in large pods,
Dusky Dolphins are firm favourites with dolphin-watching enthusiasts. Several
boat operators from Kaikoura, on New Zealand South Island are either dedicated
to watching Duskys or watch them in combination with tours aimed at watching
Dusky dolphins are one of, if not the most, acrobatic of dolphins. Spectacular leaps, somersaults and side slaps are common, and are often repeated many times in succession by an individual animal. Duskies also readily approach boats to bowride. These dolphins can be found in groups of over 1500 animals, though group sizes of 6-300 are more common. Duskies feed on organisms associated with the Deep Scattering Layer, mainly squid and in deep waters, fishes and lanternfishes, though diet differs in different regions. Cooperative foraging on southern anchovy has been reported off Argentina and on yellow-eyed mullet off New Zealand. There, several dolphins work together to keep a school of fish in a tight ball at the surface, where members of a group can take turns feeding. Feeding bouts where this balling technique has been observed last longer than bouts where individuals feed separately. Many different species of cetaceans have been seen in association with duskies, including sperm whales, bottlenose, common and southern right whale dolphins. The oldest known dusky dolphin was from New Zealand and is estimated by dentinal or tooth growth layers to be between 35-36 years old, relatively old for a moderately sized dolphin.
Dusky dolphins have been captured for public display in South Africa and New Zealand. In fact, between 1961 and 1981, 37 dusky dolphins have bee captured for this purpose, some remaining in public display facilities in South Africa. In the past, these dolphins have also been harpooned as well as caught and killed in nets for human consumption along Cape Peninsula, South Africa. Other individuals have been incidentally killed in South African purse seines; also a significant problem in areas of South America and New Zealand. Probably the most serious threat to this species comes from the fisheries off Peru and Chile, where thousands of dusky dolphins have been killed for crab bait and human consumption. One year, the annual catch from just one Peruvian port totaled more than 700 dusky dolphins. Since 1997, this dolphin "fishery" is reported to have been discontinued or at least strongly curtailed.
In New Zealand, commercially-permitted operators can take hundreds of paying customers per week to swim with free-ranging dusky dolphins off Kaikoura, South Island. Though obviously less of a severe problem than the one faced by duskies in Peru, more work is necessary to determine the potential short and long-term impact these tourist industries may be having on the dolphins.
This dolphin is restricted to the southern hemisphere, in the waters of southern Africa, New Zealand and South America. Whithin these localities they are quite common. The dusky dolphin eats anchovies in surface waters during the summer, but may also dive for squid and lantern fishes.
The dusky dolphin, or Lagenorhynchus obscuratus, is small, usually measuring between 1.6 and 2m in length. It prefers to live in large herds which may separate into sub groups to feed.
To learn more about dusky dolphins try these sources:
Brownell, R. L. Jr. and F. Cipriano. Dusky dolphin Lagenorhynchus obscurus (Gray, 1828). Ridgway, S. H. and R. Harrison (Ed.). Handbook of Marine Mammals, Vol. 6. Handbook of Marine Mammals. Academic Press, Ltd.: London, England, UK. In press.
Jefferson, T.A., Leatherwood, S. and M.A. Webber. 1994. FAO Species Identification Guide, Marine Mammals of the World. FAO of the United Nations, Rome.
Leatherwood, S. and R.R. Reeves. 1983. The Sierra Club Handbook of Whales and Dolphins. Sierra Club Books, San Francisco.
Van Waerebeek, K. and A. J. Read. 1990. Catch of small cetaceans at Pucusana Port, central Peru, during 1987. Biological Conservation. 51: 15-22.
Würsig, B., Cipriano, F., Slooten, E., Constantine, R., Barr, K., and S. Yin. 1997. Dusky dolphins (Lagenorhynchus obscurus) off New Zealand: Status of Present Knowledge. Reports of the International Whaling Commission, 47: 715-722.
Würsig and Würsig. 1980. Behavior and ecology of the dusky dolphin, Lagenorhynchus obscurus, in the south Atlantic. Fishery Bulletin. 77: 871-890.
National Audubon Society: Guide to Marine Mammals of the World.
Encyclopedia of Marine Mammals