……objective science for conservation…….

The Pacific WildLife Foundation is a non-profit coastal and marine research and education society  that inspires an appreciation for objective scientific research and conservation of the ocean. We conduct original research, develop novel education programs, and inspire an appreciation for conservation of the ocean. 

 
 
 Home
 Projects
 The Pacific
 Invertebrates
 Fish
 Birds
 Mammals
 Marine Mammals
 About Us
 Wildlife Video
 Partners
 Contact Us
 Get Involved
 Site Map
 

If you would like to make a donation to The Pacific WildLife Foundation you can use our secure online site or your donation can be mailed to our office.

Click Here for Donation Info

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

References

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

 

 
  Terms of Use  Privacy Policy