October 21, 2014   •  
Bottlenose dolphin

Risso's dolphin



Latin Name: Grampus griseus
Family: Delphinidae
Size: 3.0 – 3.8 m
Weight: 300-500kg
Group size: Small groups of 12-24 animals


Appearance

  • Extensively scarred, robust grey body
  • Large sickle shaped dorsal fin positioned in the middle of the back
  • Beakless, bulbous, square head
  • Long pointed pectoral fins

Identification

  • Surface active; seen breaching and spyhopping
  • Forms groups with other species of cetacean, usually bottlenose dolphins

Distribution

bottlenose dolphin groupScotland is at the northern most limit of the Risso’s dolphin global range. They are widely distributed through temperate and tropical regions across the world. The number of animals in Scotland is currently unknown. Risso’s dolphins are present all year round; most commonly seen from May to October peaking August and September. Areas thought to be particularly important for Risso’s dolphins include: The Outer Hebrides, particularly the Isle of Lewis, and Shetland.

Description

bottlenose dolphin groupRisso’s dolphins are a large robust dolphin with a blunt head, tall dorsal fin and extensive scarring. Animals are born a darker olive-brown colour, becoming much paler grey as they get older. Risso’s dolphins acquire obvious white scratches caused by interactions with other dolphins and from the squid they feed on. These scratches are most prominent around the head with older animals sometimes appearing almost white.

The darkest parts of the animal will be the dorsal fin, pectoral fins and fluke. The dorsal fin is tall in relation to animal size, curved backwards, positioned in the middle of the back. Risso’s dolphins also have a distinct beakless, bulbous square head and long pointed pectoral fins making them easy to distinguish from other species.

Behaviour

bottlenose dolphin group Risso’s dolphins are usually sighted in small family groups of between 10 -30 animals. They are known to associate with other cetaceans and have been seen swimming in groups with long-finned pilot whales, bottlenose dolphins, and white-beaked and Atlantic white-sided dolphins. The surfacing pattern is rather low but the tall falcate dorsal fin is conspicuous even when animals are very calm.

Risso's dolphins can be highly active at the surface often seen breaching and spyhopping at which point the long, pointed pectoral fins will be visible. Risso's dolphins generally prefer deeper offshore waters where they feed almost exclusively on squid, and have been seen forming lines when hunting.

Distribution map

Key:

(dark blue) Regular/Common
(light blue) Occasional

Risso's dolphin distribution map

Behaviours

Surface

Risso's dolphin surface

Breach

Risso's dolphin breach

Surface Animation

Video Feature

More Species

Further information

WDC Species Guide • Adopt a dolphin