Delphinus delphis – common dolphin
Delphinus delphis L., 1758
Family: Ziphiidae
Common dolphins, as their name suggests, are one of the most plentiful dolphin species in the world. They are found mainly in deep, temperate and tropical offshore waters throughout the world but can occasionally be seen in the coastal waters off Northern Ireland. A distinctive pale yellow and grey, hour-glass pattern on both sides of the body allows the common dolphin to be easily recognized. Well known for their acrobatic displays, they will approach boats and are often seen bow-riding.
In brief
- Occasionally seen in the seas around Northern Ireland
- Distinctive hour-glass pattern on both sides of the body
- Very acrobatic dolphin; often seen bow-riding
- 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
The common dolphin is small (adults are 1.7-2.6m long), with a slim and streamlined body. The back, fins and beak are dark brown/black and the underside is white. There is a distinctive hourglass pattern on the sides made up of patches of pale yellow/tan and light grey. The eye is surrounded by a black ring with a dark stripe that runs from the eye to the front of the head (above the beak). A second dark stripe runs from below the beak to the flipper. The short, narrow beak is easily seen. Between 40 and 55 pairs of small, pointed, cone-shaped teeth are present in the upper and lower jaw. The dorsal fin is in the middle of the back.
Life cycle
Common dolphins live in groups or herds that can range in size from a few individuals to several hundred. They feed mainly on schooling fish, such as herring, but will also take squid, shrimps and crabs. Groups of dolphins will often cooperate when hunting and catching schools of fish. They regularly feed in deep water and can dive to 280m. Like many dolphin species, they use echolocation to determine the shape, size, speed, distance and structure of objects in their surroundings. Common dolphins are very vocal, producing a variety of clicks and whistles that can occasionally be heard above the water. They are fast swimmers, very acrobatic and will often approach boats to bow-ride. A single calf is born in the summer.
Similar species
There are no similar species in Northern Ireland coastal waters.
How to see this species
There have been a few sightings of common dolphins in the coastal waters off Northern Ireland in recent years. The coastline around Larne/Islandmagee, the waters off Rathlin Island (both in County Antrim) and the Copeland Islands, County Down are all areas where you may be lucky enough to see this species.
Current status
The estimated population of common dolphins in the European Atlantic is about 118,000 individuals.
- 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
Common 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 common dolphin sightings to CEDaR, telephone 028 90395264 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 Committee (JNCC) priority species page
NBN Gateway: Common Dolphin (Delphinus delphis) grid map
Cetaceans of Northern Ireland - Sea Watch Foundation
Literature
Text written by:
Angela Ross
iNaturalist: Species account : iNaturalist World Species Observations database