Mammals · Artiodactyla · Delphinidae

Risso's Dolphin

Grampus griseus

Least Concern

The species is abundant and widely distributed; it faces no significant short-term risk. See full glossary

Risso's dolphin — known in Spanish as calderón gris or delfín de Risso — is a large odontocete with a blunt head, no distinct beak and a tall, falcate dorsal fin. It is teuthophagous: it feeds almost exclusively on squid, which it hunts at night when they rise towards the surface, diving to several hundred metres. It lives in groups of between ten and thirty animals and is found throughout almost all temperate and warm seas, including the Mediterranean, where it is regular in the Alborán Sea and the Gulf of Lion.

Weight

300 kg – 500 kg

Size

2.6 m – 4 m

Lifespan

35 years

Diet

Carnivore

Feeds mainly on other animals.

Activity

Nocturnal

Active mainly at night.

Social structure

Herd

Lives in large groups as a strategy against predators.

Sighting difficulty

Easy

OceanCarnivore Nocturnal In herds Ocean Mammal

161countries 59parks 91dive sites17same family

Fun facts

anatomíaIts skin is usually covered in white scars, from fights with others of its kind and from struggles with the squid it mainly eats.
Adults are covered in white scars caused by the teeth of other Risso's dolphins and by the beaks and suckers of squid; with age they come to look almost white.
It has teeth only in the lower jaw, between two and seven pairs, because it swallows its prey whole.
It is born dark grey and turns almost white with age, because it accumulates scars. The criss-cross scratches are made by other Risso's dolphins with their teeth, and the circular marks are left by squid, lampreys and the cookiecutter shark.
It has two to seven pairs of teeth, and only in the lower jaw. That is an extremely low count for a cetacean, and it is thought to keep them mainly for their role in fights between males.
It is a strict teuthophage: it eats almost exclusively squid, and hunts mostly at night.
It dives to more than 600 m by emptying its lungs and descending almost vertically with several spins, a technique that saves it time and leaves it more minutes for hunting below.
An individual called Pelorus Jack accompanied for years the ships entering Admiralty Bay, in New Zealand, and came to be protected by a specific decree.
It is the fifth-largest member of the dolphin family.

Life cycle & biology

Skeleton type: Vertebrate - internal bony skeleton (mammal)
Habitat & environment: Temperate and tropical waters of every ocean, above all over the continental slope
Sexual maturity: 10 years
Gestation / incubation: 12 months
Litter / clutch size: 1

Sources consulted: https://www.iucnredlist.org/ | https://animaldiversity.org/ | https://es.wikipedia.org/