by: Nicole Le Boeuf
This dolphin's name comes from its tendency to leap into the air and spin on its long axis several times before falling back into the water. The word Stenella from the Greek word stenos for "narrow" apparently refers to the long, narrow rostrum. This description is reconfirmed by the derivation of the word longirostris, from the Latin words, longus for "long beak".
The spinner dolphin is quite slender with a long, thin rostrum. Its dorsal fin varies greatly from falcate to triangular and even canted forward in the Costa Rican population; moreso in the adult males. Three discrete subspecies have been described with slight differences in appearance. However, the generally have dark stripes running from the eyes to flippers. Their lips and end of the beak are also darkly colored. The rest of their markings and coloration range from dark gray to white on the belly. These variations are due to the genetic separation of the stocks.
Along with differences in markings, there are also some differences in the overall build of the animal between the populations. Some are more slender or stockier than others. Overall, spinner dolphins are about 2-2.5 m long at adulthood with males being a bit larger than females. Their weight tends to be at least 77 kg.
Spinner dolphins are found in an almost all the world's oceans, but are restricted to tropical, subtropical, and warm temperate waters. They are generally found in pelagic waters, and specimens have been taken from Madagascar as well as from Eastern and Western Africa.
Besides their remarkable aerial acrobatics, spinners are also well-known for their extreme gregarious nature as they often travel in groups of several hundred to several thousand individuals. They are also sometimes associated with pan-tropical spotted dolphins as well as common dolphins.
Their strong herding instincts, as well as their close association with yellowfin tuna, makes them quite vulnerable to incidental capture in the tuna industry purse seine fisheries in the Eastern Tropical Pacific Ocean. Because of this, their populations in this region of the world have been greatly reduced in recent decades. There is also probably fisheries interactions off West Africa.
Insufficiently known.
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 Fransisco.
Jefferson, T.A., Curry, B.E., Leatherwood, S. and J.A. Powell. 1997. Dolphins and porpoises of West Africa: A review of records (Cetacea: Delphinidae, Phocoenidae). Mammalia, v61 i1 pp 87-108 (22).
Norris, K. 1991. Dolphin Days The Life and Times of the Spinner Dolphin W.W. Norton & Co.
Norris, K.S., Wursig, B., Wells, R.S., Wursig, M., Brownlee, S, Johnson, C., and J. Solow. The behavior of the Hawaiian spinner dolphin. Administrative Rept., LJ-85006C. National Marine Fisheries Service, Southwest Fisheries Laboratory, La Jolla, California, 1-213.
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