by: Nicole Le Boeuf
The word Grampus is Latin for "a kind of whale" and the word griseus is Latin for "gray".
Risso's dolphin adults range from dark gray to white with extensive scarring in the form of white scrapes and spots. There is a white patch on the chest, a tall, slender, and falcate dorsal fin, flippers, and flukes are dark in color. There are also dark rings around the eyes. This species has no beak, but instead possesses a squarish melon with a deep, vertical crease on it. Their mouth angles slightly upward. It has a robust body, and its appendages are large. Once they've reached adulthood, this species is generally unmistakable.
When they are born, Rissos' are about 1.5 m long. As adults, Risso's dolphins grow to be about 3.6-4 m with no known difference between the sexes. They generally weigh up to 400 kg.
This dolphin species is cosmopolitan throughout the world's tropical and warm temperate waters. Part of their southernmost range includes the waters off South Africa, but they can be found in all African waters.
Although they usually travel in moderately-sized groups, aggregations of up to 4000 individuals have been observed. Risso's dolphins are often seen traveling with other species of cetacean. Their dentition is unusual in that they 2-7 pairs of teeth in the front of their lower jaw, but usually none in their upper jaw. Hybridization of Rissos' and bottlenose dolphins have been observed in the wild as well as in captivity.
Risso's dolphin are taken in small numbers throughout their range accidentally as well as intentionally. However, their mortality levels are poorly documented and considered insignificant to their overall health of their abundant population.
Insufficiently known.
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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).
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Wuertz M. Poggi R. Clarke M R. CEPHALOPODS FROM THE STOMACHS OF A RISSO'S DOLPHIN GRAMPUS-GRISEUS FROM THE MEDITERRANEAN. Journal of the Marine Biological Association of the United Kingdom 72 (4). 1992. 861-867.
Marine Mammal Stranding Center
URL for this page: http://csiwhalesalive.org/csirissos.html