Northern Ireland's Priority Species

Grampus griseus – Risso's dolphin

 
Grampus griseus
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Grampus griseus Cuvier, 1812
Family: Ziphiidae

Risso’s dolphin occurs in tropical and temperate seas around the world. It is usually found in deep offshore waters but small groups of 2-15 individuals are occasionally seen in Northern Ireland coastal waters, usually between May and September. Although they will occasionally approach boats and swim alongside, they do not usually bow-ride.

In brief

  • Occasionally seen in the seas around Northern Ireland
  • Dark to light grey, back and head with extensive pale scratches and scars
  • No distinctive beak
  • Listed as a UK Priority species
  • Main threats to the population are accidental capture and drowning in commercial fishing equipment (by-catch) and pollution

Species description
Risso’s dolphin is a large dolphin (adults are 2.6-3.8m long). The body colour changes with age; young animals range from dark grey to brown, while older animals are mainly pale grey with almost white faces. As the animal ages, the body becomes covered with distinctive pale scarring. The forehead bulges slightly and the face is blunt with no beak. A distinctive V-shaped crease is present on the top of the head and runs from the blow hole to the upper lip. There are 4-14 oval shaped teeth, usually only in the front of the lower jaw. The dorsal fin is large (up to 50cm tall) and in the middle of the back. The tail is slightly notched in the middle.

Life cycle
Risso’s dolphin is highly sociable; large groups of over 1,000 individuals have been seen where food is plentiful. They feed on squid, octopus and cuttlefish, often at night when their prey moves closer to the surface of the water. Individuals will cooperate together when hunting.

Similar species
Risso’s dolphin may be confused with either the bottlenose dolphin or the killer whale. The easiest way to tell the species apart is by body shape and colouration. Killer whales have very obvious black and white markings, while Risso’s dolphins are dark/pale grey with pale, criss-cross scarring that is easily visible, even at a distance. The bottlenose dolphin has a noticable beak, unlike Risso’s dolphin which has a blunt, rounded head with no beak.

How to see this species
There have been occasional sightings of Risso’s dolphin off the coast of Northern Ireland. The coastline around Islandmagee and the waters off Rathlin Island (both in County Antrim) and the Copeland Islands (County Down) are all areas where you might see this species.

Current status
There is no information available on the status of Risso’s dolphin in Northern Ireland waters.

  • Protected under schedule 5 of the Wildlife (Northern Ireland) Order 1985
  • Listed in Schedule 2 of The Conservation of Habitats and Species Regulations 2010
  • Listed in Appendix II of the Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention)
  • Listed in Appendix II of the Convention on the Conservation of Migratory Species (The Bonn Convention)
  • Covered by the terms of the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS)
  • Listed in Appendix II of CITES
  • Listed in Annex A of EU Council Regulation 338/97 and therefore treated by the EU as if they are on CITES, Appendix I
  • Listed in Annex IV (Animal and Plant Species of Community Interest in Need of Strict Protection) of the EC Habitats Directive
  • Listed in Schedule 2 of The Conservation (Natural Habitats, etc.) Regulations (Northern Ireland) 1995

Why is this species a priority in Northern Ireland?

  • Listed as a UK Priority species

Threats/Causes of decline

  • Entanglement in fishing gear (by-catch)
  • Reduction in fish numbers due to commercial fishing
  • Disturbance and/or injury by sea vessels
  • Pollution (chemical and noise)

Conservation of this species

Current action
Risso’s dolphins are included in the UK Grouped Species Action Plan for small dolphins, which was published in 1999.

  • Post mortem and tissue studies are carried out on stranded dolphins to establish the cause of death and condition of the animals at the time of death
  • In 2008 the Northern Ireland Environment Agency initiated a cetacean monitoring programme to provide information on the distribution and relative abundance of cetaceans in Northern Ireland waters. The information collected will enable the future selection of marine protected areas for cetaceans

Proposed objectives/actions

  • Avoid accidental harm to whales and dolphins when present in Northern Ireland waters
  • Contribute to international measures for the conservation of whales and dolphins

What you can do
To report Risso’s dolphin sightings to CEDaR, Telephone 028 9039 5264 or email cedar.info@nmni.com.

Further information

Links
Irish Cetacean Review 2000-2009, The Irish Whale and Dolphin Group UK Grouped Species Action Plan for small dolphins

Joint Nature Conservation Commitee (JNCC) priority species page

NBN Gateway: Risso's Dolphin (Grampus griseus) grid map

Irish Whale and Dolphin Group

Cetaceans of Northern Ireland - Sea Watch Foundation

Literature

Text written by:
Angela Ross