Risso’s Dolphin

General information
Quick Facts
Order Cetacea
Suborder Odontoceti
Family Grampus
Species Grampus griseus
Status Common
Weight Up to 1100 pounds
Diet Primarily squid, but some fish too
Size Up to 13 feet
Home Worldwide in tropical and temperate waters

Why is a Risso’s Dolphin so Scarred?

When a Risso’s dolphin is young, it is slate-gray to black with no scarring. As they age, they lighten in color and acquire white scars all over their body. These scars are assumed to be from the teeth of other Risso’s dolphins (called rake marks) and from the squid that they eat which have sharp hooks on their tentacles. Eventually, the Risso’s dolphin can be almost completely white. This striking coloration along with the absence of a beak make the Risso’s Dolphin easy to identify. Risso’s specialize in eating squid, but may consume some fish as well. They eat primarily at night as their prey species migrate toward the surface to feed.

A Relative Newcomer

Risso’s have not always been found off the coast of Dana Point. In a 1995 paper, Susan Shane documented a shift in observed species from Long-finned Pilot Whales to Risso’s Dolphins which took place around the 1982-83 El Nino event. Aggressive behavior of the Risso’s toward the Pilot Whales was observed and may have resulted in a competitive displacement since they both specialize in the same food type. Since then, Pilot whales have not been present, but Risso’s are frequently sighted.