Risso's Dolphin

Grampus griseus

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This is a medium-sized dolphin with a robust body and a slender tail. Adult males and females are roughly the same size, reaching lengths up to 13 feet (4 m) and weight 1,100 lbs (500 kg). They have a large, rounded head with a blunted beak. The dorsal fin is tall and sickle-shaped. As the dolphin ages, its coloration will change dramatically. Younger individuals are black, while older dolphins range between gray, brown and white. Their skin often appears mottled due to heavy scarring caused by by other dolphins raking their teeth across the skin during play or mating. Additional injuries can be caused by squid and Cookie-Cutter Sharks. Interestingly, the Risso’s Dolphin has no teeth in its upper jaw.

The Risso’s Dolphin does not congregate in large numbers like other dolphin species. Often they will live solitary lives or in small pods of no more than 30 individuals. They engage in a variety of behaviors when surfacing, including spyhopping and lobtailing. Their food sources include anchovies, krill, squid, octopus and cuttlefish.

Range and Habitat

Populations of Risso’s Dolphins can be found in U.S. waters around the Hawaiian islands, the West Coast, the northern Gulf of Mexico and the north Atlantic seaboard. This dolphin prefers the open sea and may be more numerous along or beyond the continental shelf.

Conservation Status

There is currently insufficient data to assess the global health of this species, but they are generally considered common in U.S. water. The California / Oregon / Washington stock is estimated to number up to 16,000 animals. Like all cetaceans, the Risso’s Dolphin is protected from hunting by the Marine Mammal Protection Act of 1972.