Biodiversity & Conservation

Risso's dolphin - Grampus griseus

Grampus griseus

Image Colin Speedie - Risso's dolphin at Coverack. Image width ca 4 m.
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Distribution map

Grampus griseus recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

Why do the maps differ?

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  • CITES
  • EC_Habitats
  • WC_Act_1981
  • NI_Act
  • UK_BAP
Taxonomy icon Taxonomy Taxon English term
Phylum Chordata Sea squirts, fish, reptiles, birds and mammals
Class Mammalia Seals, walrus, dolphin and whales
Authority Cuvier, 1812
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland This species has been recorded off the Hebrides, Scottish Minches and in the Irish Sea, especially near Bardsey Island off the north Welsh coast. It may also be expected off the Shetland Isles and west coasts of the British Isles and Ireland.
Habitat information icon Habitat information Grampus griseus is a deep water species sighted close to shore where the continental shelf is narrow and around oceanic islands. It prefers tropical and warm temperate water migrating north in the summer months.
Text page icon Description Grampus griseus has a robust body up to 4 meters in length and weighs up to 600 kg. Males of the species are larger than females. Colouration varies individually and with age. 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.
Additional information icon Additional information Grampus griseus is one of the largest members of the Delphinidae family. 'Grampus' meaning 'grand fish', and 'griseus' referring to its grey colouration. 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 by Grampus griseus during play, aggression and sexual behaviour, as well as confrontations with cephalopod species (to a lesser degree) (Carwardine, 2000). 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 (Martin, 1990; Carwardine, 2000). 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. It also takes a dozen breaths every 15-20 seconds, and seldom bow-rides. Full breaching occurs in the young and half breaching in adults (Carwardine, 2000). This species occurs in groups of about 12, and can aggregate into large of herds, up to 4000 individuals has been recorded. This species feeds on pelagic fish and cephalopods, favouring squid. Hybrids of Grampus griseus and Bottlenose dolphin, Tursiops truncatus, have also been reported in the wild (Kinze, 2002).

This species is subject to by-catch, and is included in the UK Biodiversity Action Plan list of species of conservation concern (Biodiversity Steering Group, 1995). All species of cetaceans are given protection under the Wildlife and Countryside Act 1981 and the Wildlife (Northern Ireland) Order 1985. All cetacean species are listed on Annex A of EU Council Regulation 338/97 and therefore treated by the EU as if they are on CITES Appendix I therefore prohibiting their commercial trade. Risso's dolphin is also listed on Annex IV of the EC Habitats Directive, which prohibits all killing, capture, disturbance, sale, exchange or keeping of the animials. The directive requires that all accidental killing and capture be monitored by all member states. Also this species is listed under Appendix II of the Bonn Convention (North and Baltic Sea populations), and Appendix II of the Bern Convention. The Bonn Convention is the parent Convention to the 'Agreement on the Conservation of Small Cetaceans in the Baltic and the North Seas' (ASCOBANS) formulated in 1992. The UK is one of seven European countries which have signed the agreement which includes the protection of specific areas, monitoring, research, information exchange, pollution control and heightened public awareness. Measures included are specifically aimed at protecting dolphins and porpoises in the North Baltic Seas (Anon, 1999e).

This review can be cited as follows:

Sonia Rowley 2005. Grampus griseus. Risso's dolphin. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 04/02/2012]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=3419>