Taxonomy
Grampus griseus | Risso's Dolphin
Distribution
Status
Conservation status
| HABITATS DIRECTIVE ARTICLE 17 REPORTING |
| Range | Favourable |
| Population | Unknown |
| Habitat | Favourable |
| Future Prospects | Unknown |
| Overall Assessment of Conservation Status | Unknown |
| Overall Trend in Conservation Status | N/A |
IUCN Conservation Status |
| Ireland | Not evaluated* |
| Europe (1) | Data deficient |
| Global (2) | Least concern |
* There is currently no Irish Red List for Marine Mammals.
Legal status
Protected by the following legal instruments:
- Habitats Directive (92/43/EEC) Annex IV
- Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention) Appendix II
- Convention on the Conservation of Migratory Species of Wild Animals (Bonn Convention) Appendix II*
- Convention on Trade in Endangered Species of Wild Fauna and Flora Appendix (CITES) II
- Council Regulation (EC) No. 812/2004
- Wildlife Act (1976)
- Wildlife (Amendment) Act (2000)
- Whale Fisheries Act 1937
Native status
Recent mapping efforts recorded no individuals in Irish waters between November and March. Peak recordings were in summer months and the presence of young calves in observed groups indicate that the species may calve in Irish waters.
Source: Wall, D. et al 2013.
The 2012 IUCN Global Red List for this species lists Ireland as one of the countries where it is native, however it probably better described as a migrant in an Irish context.
Sources: Taylor, B.L. et al 2012; de Klem, 1994.
Species Biology
Identification
- Max. adult body length: 3.8m
- Max. adult body weight; 500kg
- Average adult body length: 3.2m
- Average adult body weight: 400kg
- Average length of calf at birth: 1.5m
- Average weight of calf at birth: Unknown
- Blow: Generally only seen at close range
- Head: The head is blunt and bulbous, sloping steeply to the mouth, with no beak. Risso's dolphin has an odd, deep V-shaped crease, which extends from the blowhole to the tip of the rostrum (to the upper lip) bisecting the forehead. This crease is visible at close range and is unique to this species. The eye is prominent. The mouth slants upwards towards the eyes.
- Dorsal Fin: The dorsal fin is prominent, tall and dark, located mid-way along the back. Due to its size (up to 50cm high) can often lead to confusion with Killer Whale or Bottlenose Dolphin. The tip may be rounded or pointed with a concave trailing edge.
- Pectoral Fins: Pectoral fins are long, dark and sickle shaped.
- Colouration: Risso's dolphins can show immense variation in colouration. At birth the calf is uniformly grey (overall colour ranging from light to dark grey) with seven pale vertical stripes. They soon lose this juvenile colouring becoming a dark grey, turning to a chocolate brown as a juvenile. As they age the adult Risso's becomes paler and paler with body colour fading to a pale grey or even becoming as white as a Beluga, particularly around the head. White scarring found on the body may provide identification features for individuals.
- Markings: There is a whitish anchor shaped patch on the chest and the underside of the belly is also typically white, although this may vary. They have a distinctively battered appearance with extensive body scarring caused by the teeth of other Risso's dolphins and circular marks on the body caused by one of their main prey items - squid.
Habitat
Generally Risso's Dolphin is considered a species more likely to be found in deeper waters over continental shelf slope and beyond. In Irish waters however this species is most often recorded over continental shelf.
Source: Wall D. et al 2013.
Habitats include but are not necessarily limited to;
- Open marine water (MW1)
Sources: Harris S., Yalden D.W. 2008.; Fossitt, J.A., 2001.
Reproduction
- Maximum recorded age: 29 years.
- Sexual maturity: 3-4 years.
- Gestation: c. 14 months.
- Calving: March -June.
Risso's dolphins breed in Irish waters, one was born in Blacksod Bay in Co. Mayo in the 1930's, whilst a young calf showing colouration typical of a young Risso's stranded at Rosbrin Cove (Co. Cork) in 1990.
Source: Irish Whale and Dolphin Group.
Threats faced
| THREAT | ARTICLE 17 THREAT CODE | RANKING |
| Fishing and harvesting aquatic resources* | F02 | Medium |
| Seismic exploration, explosions | H06.05 | Medium |
| Death or injury by collision | G05.11 | Low |
| Noise nuisance, noise pollution | H06.01 | Low |
| Marine water pollution | H03 | Low |
| Changes in abiotic conditions | M01 | Low |
| Threats and pressures from outside the EU territory | XE | Low |
| Threats and pressures from outside the member state | XO | Low |
*This would include the threat to this species of becoming by-catch / accidental catch as well as the threat of a reduction in prey availability and also entanglement in fishing gear.
These threats accord well with threats outlined in the 2007 European Regional IUCN Red List assessment for the species which did not identify any other threats that may be relevant in Irish waters.
Source: IUCN SSC Cetacean Specialist Group 2007.
Conservation actions
In the Article 17 Habitats Directive reporting for the period 2007-2012 no Conservation Measures in place or in the process of being implemented were listed.
Source: NPWS 2013.In addition to an acknowledgement of the existence of legislative protection, suggested Conservation Actions in the global 2012 IUCN Red List assessment for this species included;
- Data on abundance, bycatch, and behaviour needed.
In a 2009 Cetacean Action Plan a total of 41 Actions were identified as part of the plan. The plan and the 2013 review of the plan are available from the NPWS website.
Source: DEHLG 2009.
Distribution
World distribution(GBIF)
Risso's dolphins are fairly abundant with a world-wide distribution in tropical and temperate seas, but do not generally penetrate far into high latitudes.
In the North Atlantic, they have been reported from Newfoundland in the west and the Shetland Islands off Scotland in the east, south to the Lesser Antilles in the Caribbean and the Azores and Mediterranean. They are sighted regularly around the Irish coast, with sightings and strandings concentrated on the south-west and west coast of Ireland, with occasional sightings in the Irish Sea.
In the south Atlantic, they have been sighted as far south as Argentina and South Africa. In the Pacific, they are found as far north as Alaska and the Bering Sea, off British Columbia and the Kurile Islands, and south to Central Chile and Cape Horn.
They are present in the Red Sea, are distributed throughout the Indian Ocean and as far south as New Zealand and Australia. They may also be seen in the South China Sea, Philippine Sea, off the Solomon Islands and New Guinea.
Source: Irish Whale and Dolphin Group.
Accuracy of world distribution shown in the Global Biodiversity Information Facility (GBIF) map below will be constrained by, amongst other factors, data held but not shared by countries and organizations not participating in the GBIF.
Irish distribution
Highest relative abundance off southwest and southeast coasts, although this species has been recorded all round the Irish coast. Most often in offshore waters over the continental shelf although also recorded in inshore waters.
Source: Wall, D. et al 2013.
Temporal change
Records submitted to Data Centre in 2024
The following map is interactive. If you would prefer to view it full screen then click here.
How can you help
The National Biodiversity Data Centre is trying to
improve our knowledge of the distribution of the Risso's Dolphin in
Ireland. Should you observe this species, please submit
sightings to add to the database. Detailed observations will assist us
gaining a better insight into where the species
is most abundant in Ireland and we might also be able to detect
regional variations. Please submit any sightings and photographs at:
http://records.biodiversityireland.ie/index.php
All
records submitted online can be viewed on Google Maps – once checked
and validated these will be added to the database and made available for
conservation and research.
Further information
For further information contact Dr. Liam Lysaght llysaght@biodiversityireland.ie
References
Publications
DEHLG (2009) Conservation Plan for Cetaceans in Irish waters.
Fossitt, J.A. (2001) A Guide to Habitats in Ireland. The Heritage Council
Harris S., Yalden D.W. (2008). Mammals of the British Isles :Handbook, 4th Edition. The Mammal Society.
Species account by IUCN SSC Cetacean Specialist Group; regional assessment by European Mammal Assessment team 2007. Grampus griseus. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 14 October 2014.
NPWS (2013) The Status of EU Protected Habitats and Species in Ireland. Species Assessments Volume 3. Version 1.0. Unpublished Report, National Parks & Wildlife Services. Department of Arts, Heritage and the Gaeltacht, Dublin, Ireland.
NPWS (2013a) Delivery Schedule for Actions listed in the Conservation Plan for Cetaceans in Irish waters – June 2013
Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J.K.B., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L. 2012. Grampus griseus. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 14 October 2014.
Wall, D., Murray, C., O’Brien, J., Kavanagh, L., Wilson, C., Ryan, C., Glanville, B., Williams, D., Enlander, I., O’Connor, I., McGrath, D., Whooley, P. & Berrow, S. (2013). Atlas of the Distribution and Relative Abundance of Marine Mammals in Irish Offshore Waters: 2005 – 2011. Irish Whale and Dolphin Group, Kilrush, Co. Clare.