This dolphin has a rather stocky body with a rounded head and no rostrum, and it has only conical teeth on its jaw. At birth, Risso’s dolphins are a uniform light grey; over time, however, the skin acquires those light scars that make this species unmistakable. The marks, caused by the teeth of conspecifics, accumulate year after year to the point that older individuals can appear almost completely white.
As in all cetaceans, Risso’s dolphins are born in breech position.
The Risso’s dolphin lives in shoals consisting of a few to several dozen individuals. It generally swims rather slowly, at around 6-7 km/h; it prefers steep seabeds at 200 - 2000 metres depth where it hunts mesopelagic squids, mainly at night. Shy in nature, Risso’s dolphins do not often allow boats to approach and rarely make jumps out of the water. In the Mediterranean, they have also occasionally been observed in mixed groups including striped dolphins, common dolphins, and sperm whales. Although regularly reported since the early 1990s, sightings of this species have decreased in the western portion of the Sanctuary since 2014.
Scars all over the body and notches on the posterior margin of the dorsal fin.
Its body is strewn with light-coloured scratches that accumulate over time
A typical, yet unusual posture of the Risso’s dolphin is a head-down, upright position with the tail protruding above the water’s surface, which can last for 10-20 seconds. The meaning of this behaviour, called head-standing, is not yet understood. The Risso’s dolphin mainly communicates using vocalizations that our ear perceives as a sort of “murmur”.
