Local Names: Grampus; Grey Grampus; White-Head Grampus; Grey Dolphin. Confusingly, several members of the 'Blackfish' family, in particular the immense Orca (Killer Whale) were called 'Grampus' in older literature and are sometimes still referred to as such.

Description: This is a more 'barrel-shaped' dolphin with a large blunt head and no beak. In this respect it is similar to the large Sperm Whale. Risso's Dolphins vary in color from blue-grey, grey-brown or almost-white, depending on age and injuries. Scars from other male Risso's Dolphins can often be seen, dark on lighter individuals and light on darker individuals. The mouth slants upwards and there are seven or fewer pairs of teeth at the front of the lower jaw. The dorsal fin is tall and curved, with a distinct point at the tip, rather like the flippers. The tail stock is thick and ends in powerful flukes. Adults range from about 2.6 to 3.8m (8.5 to 12.5ft), and new-borns from 1.3 to 1.7m (4.25 to 5.75ft).



Recognition at sea: Robust body, abrupt forehead, single blowhole, grey in color, lighter under-side (belly), tall dorsal fin, white scratches and scars.The adult Risso's Dolphin is quite easy to recognize at sea with their distinctive scarring. The scarring occurs during their mating rituals.



Habitat: Risso's Dolphins prefer warm temperate and tropical offshore waters, they have been found in temperatures ranging from 4.5 to 28 degrees celsius and are only seen close to shore when the continental shelf is narrow. Risso's dolphins have been seen as far north as Newfoundland and the Shetlands (N. Atlantic), and the Gulf of Alaska (N. Pacific).They prefer deep offshore waters, although around Britain and Ireland they are usually recorded within 11km (7 miles) of the coast. Around the UK, Risso's have been spotted in the western part of the English Channel, the Irish Sea, off the coast of Dyfed in Wales, and the west coast of Scotland, around areas such as the Isle of Mull. They have been seen as far south as Cape Horn, the Cape of Good Hope, Australia and New Zealand. The migration of these dolphins is not known, although this species has been known to migrate into cooler waters during the more productive summer months in search for food.  Risso's dolphins may also migrate regionally when environmental conditions change and in search for warmer waters and more prey.

Food & Feeding: The main prey is squid and octopi but they are also known to take fish. While the size of their squid prey is unknown, squid beaks from species that grow up to 12 feet in length have been found in the stomachs of stranded Risso's dolphins.





Behavior: Risso's Dolphins are usually seen in groups of 3-50 animals. Occasional aggregations of up to 4,000 are also seen, and they often mix with other dolphin species. Risso's do not often 'bow- ride' in front of boats, but may swim beside or in the bubbly wake that a boat leaves. These groups spread out in a long line when hunting for food. Some groups are shy, but some allow humans to approach close to them. Young animals are energetic, and may breach (lift themselves out of the water), slap their flippers against the surface of the sea, 'spyhop' (lift their head above the surface to have a look around), and surf in the waves. Risso's Dolphins create a series of varying sounds including signiture whistles. Mass and individual strandings are not uncommon. While the age at which these animals reach sexual maturity is not known, it appears to occur when the dolphins are approximately 8.5 to 9.2 feet in length (2.6-2.8 m) in both sexes, and probably less than 13 years of age. Little is known about calving and breeding, but evidence from the North Atlantic Ocean indicates a summer calving season. Estimated gestation is 13-14 months. Calves are generally 4 to 5 feet long (1.2 - 1.5 m) at birth

Here is a spectrogram of Risso's dolphin whistles, coutesy of Centro di Bioacustica e Ricerche Ambientali. Universita' di Pavia.




Longevity: Risso's dolphins can live up to 30 years in the wild.



A famous Risso's dolphin named "Pelorus Jack" was known for escorting ships and into the Pelorus Sound. The crew of these ships witnessed this behavior for 24 years beginning in 1912.




The Influence of Man: In a few parts of the world, Risso's dolphins are killed for human consumption. They are commonly found in the open market in Taiwan, and they are part of the Japanese drive fishery for dolphins. Both Japan and Peru take Risso's Dolphins in drive fisheries, and small numbers are also taken in the Carribean, the Black Sea, and the Indo-Pacific Islands. This is one of the major species which Sri Lanka catches in its harpoon fisheries and gillnets. A few individuals caught alive and placed in captivity have not adapted well.

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 In 1933 Ireland, three strange dolphins were beached - the best guess as to their identity was that they were hybrids between Risso's Dolphin and the Bottlenose Dolphin. This seems certain as now captive dolphins of the two species have a hybrid calf.