Risso’s Dolphin

Grampus griseus

Scientific Classification

Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Cetartiodactyla
Suborder Odontoceti
Family Delphinidae
Genus Grampus
Species griseus

Risso’s dolphins are typically 10 to 13 ft long (3 to 4 m) and weigh 660 – 1,100 lb (300 to 500 kg).

They can live for 35 years or more.

Risso’s dolphins feed mainly on squid but also consume fish. They have no beak, no teeth on the upper jaw, and only a few on the lower jaw.

They are distributed worldwide in tropical and temperate oceans and frequent mostly continental shelf waters.

Threats to Risso’s Dolphins
Habitat shifting and alteration, fishing & harvesting of aquatic resources, anthropogenic (human-created) noise

Current Population Trend

Conservation Status
Data Deficient

The IUCN Red List tracks the conservation status of organisms around the world. Visit the Red List to learn more about the conservation status of Risso’s dolphins.

OCS Research Insights

Collecting data on Risso’s dolphins off California is hard! They are boat-shy and usually tend to dive when approached.

Learn more about OCS research

Off Los Angeles, Risso’s dolphins “replaced” pilot whales in the late 1990s. But after a few years, they moved away, following their favorite prey – squid. We now see them only occasionally.

Learn more about OCS research
Read the scientific paper

Off Southern California, Risso’s dolphins tend to form mixed groups, mostly with offshore bottlenose dolphins – and yes, we have witnessed interbreeding!

Learn more about OCS research
Read the scientific paper

Risso’s Dolphin Facts

• Infants are grayish-brown – as they mature, they become almost white from tooth marks inflicted during physical interactions with other individuals.

• A Risso’s dolphin, (called Pelorus Jack) escorted boats into Admiralty Bay in New Zealand for over 20 years!

• Risso’s are typically a deep-water species – therefore, scientists still don’t know a lot about them.


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whale and dolphin species drawings © Massimo Demma / ICRAM / Muzzio