Grampus griseus (Risso's Dolphin)
The north of Scotland is the northern limit for the distribution of Risso's Dolphin. In the Hebridean waters they tend to inhabit deeper water although they can occasionally be seen in coastal areas.
Additional Information
Hebridean Whale and Dolphin Trust
Cetacean Research & Rescue Unit
Convention on Migratory Species, Small Cetaceans Agreement, Baltic, NE Atlantic, Irish and North Seas
EC CITES Annex A
Bern Convention Appendix 2
EU Habitats Directive Annex 4
Scottish Biodiversity List of species of principal importance for biodiversity conservation
Grampus griseus has a robust body up to 4 meters in length and weighs up to 600 kg. Generally adults are medium to dark grey on the back, paler on the flanks with a marked border and a white anchor shaped patch on the belly. Dorsal fin, flippers and flukes are dark grey. This species has a large blunt head, no beak and a characteristic crease on its forehead from the blowhole to the upper 'lip'. The mouth line is straight and slants upwards slightly. There are 3-7 pairs of strong oval teeth at the tip of the lower jaw and, only occasionally are there one or two vestigial teeth on the upper jaw. Grampus griseus has a tall dorsal fin up to 60 cm high with a pointed or rounded tip. Its flippers are also pointed and up to 60 cm long. The pointed tail flukes have an expanse of up to 76 cm.
Identifying features
Blunt nose.
Vertical crease on front of head.
Up to 4 meters in length.
Grey robust body appearing white with age due to scarring.
Dark gray fin, flippers an flukes.
Tall dorsal fin up to 60 cm high.
Strong oval teeth at the tip of lower jaw.
At birth this species has a muted anchor shaped patch on its belly, and is uniformly gray becoming lighter with age. This is due to the extensive teeth scarring caused during play, aggression and sexual behaviour, as well as confrontations with cephalopod species (to a lesser degree). The white colouration in older species may confuse it with Beluga whales (Delphinapterus leucas), however Risso's tall dorsal fin is the main distinguishing feature. Gestation is 13-14 months, and sexual maturity around 3-4 years for both sexes. Calves can be up to 1.7 meters long and weight approximately 20 kg. Grampus griseus dives for 1-2 minutes but can stay submerged for up to 30 minutes. This species occurs in groups of about 12, and can aggregate into large of herds, up to 4000 individuals has been recorded.