Risso's Dolphin - Oceana Canada

Marine Mammals

Risso’s Dolphin

Grampus griseus


Grey dolphin


Temperate and tropical zones of all oceans


Deep waters off continental shelves


Carnivorous predator


Order Cetacea, Family Delphinidae


Risso’s dolphins are eye-catching with their unique colouring and white marks across their body. These white marks are actually scars left by battles with their favorite prey, octopus and squid, as well as from members of the same species. As Risso’s dolphins age, their white marks grow in number to where some adults are completely white. For a toothed whale, these dolphins don’t quite fit in – they lack teeth in their upper jaw and rely on several rows of lower teeth to eat! This usually leads to them eating squid whole. Often only found in deep waters off the continental shelf, these unique dolphins can dive up to 500 metres and hold their breath for up to 30 minutes in search of their favorite foods.


Risso’s dolphins are stocky with a blunt, rounded head instead of a beak. Their grey bodies are contrasted with white bellies and are often scarred with white markings. These white scars come from aggressive fighting as they hunt their main source of food – squid. This dolphin is relatively large, reaching lengths over four metres (13 ft) and weights of up to 500 kilograms (1100 lbs). Their dorsal fins are very predominant and tall when compared to other dolphins of their size and they are often mistaken for orca whales due to this. Their upper jaw lacks teeth and instead, they have seven rows of cone teeth in their bottom jaw.



The average lifespan of a Risso’s dolphin is 20 to 40 years. Sexual maturity occurs around the age of eight to 10 and pregnancy lasts 13 to 14 months. The dolphins have been observed living alone but are most commonly seen in pods of three to 30 individuals. There have been instances of “super-pods” where thousands have been spotted together.



In many countries, Risso’s dolphins are legally fished for meat and oil but unregulated and dangerous fishing practices can also have an impact on them. Bycatch is the unintentional catch of an animal in fishing gear. Risso’s dolphins have been recorded as pelagic long line and gillnet bycatch when squid is used as bait. Since we do not have a population estimate of these dolphins, it is unknown how detrimental these incidental or illegal catches are.



There is still much unknown about Risso’s dolphins and the full threats that they face. Under the IUCN Red List, they are listed as a Least Concern.