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Risso’s Dolphin Grampus griseus

Risso’s dolphin joins the sperm whale as denizens of deep water. They are mostly seen where water is several 100 meters deep and so they are not often seen near shore (Wilson and Ruff 1999).. The life history of this species is incomplete as a result. It prefers warm waters and enters temperate regions only in summer. It seems to live in groups that travel together among large herds numbering in the hundres or thousands (Wilson and Ruff 1999). Calves, juveniles and adults appear to segregate in these groupings. Risso’s dolphins reach sexual maturity when they are more than 2.5 m long and off California probably calve in winter.  Calves measure about 1.5 meters long and blue gray in colour. The colour turns a dark brownish-grey with age (Wilson and Ruff 1999).  This species is highly gragrious and interative. They leap and porpoise and make high speed zig-zags. Risso’s dolphins are thought to eat squid. They lack teetch in the upper jaw and only a few in the lower jaw, likely as an adaptation to eating soft bodied squid.   Risso's dolphins utter seven vocalisation types: broadband clicks, barks, buzzes, grunts, chirps, whistles, and simultaneous whistle  and burst-pulse sounds (Corkeron and Van Parijs 2001).


 Risso’s Dolphin Distribution Map

Risso’s Dolphin Distribution Map


Wilson, D. and S. Ruff. 1999. Smithsonian book of North American mammals. UBC Press, Vancouver.

Corkeron, P. and S. Van Parijs. 2001. Vocalizations of eastern Australian Risso's dolphins, Grampus griseus, Canadian Journal of Zoology 79: 160-164


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