Common Dolphin

Size: 1.7 – 2.5m
Key feature: Distinctive yellow and grey hourglass pattern
Behaviour: Energetic and acrobatic

Appearance

Common dolphins are, as the name suggests, the most common in the world. They have a beautiful striking pattern of yellow and grey panels creating a distinctive hourglass shape on their side which makes them easy to spot. Their dorsal sides are dark with a V shape below the dorsal fin. They are 1.7 – 2.5 m long, making them one of the smaller dolphins.

Behaviour

In European waters they usually travel in groups, typically comprising around 20 individuals, but have been seen in groups of over 500. In other areas worldwide they have been seen in groups of thousands. They are often seen with other dolphins, especially striped dolphins. Common dolphins are very energetic and acrobatic, often leaping out of the water, splashing and occasionally even somersaulting. They are attracted to the bows of ships, giving passengers an exhilarating display. When feeding they herd fish into a tight ball so that they can catch them more easily.

Distribution

The have a worldwide distribution from temperate to tropical regions. They prefer deeper waters and shelf seas, but are occasionally seen near the coast. They are regularly sighted from ferry trips to the Isles of Scilly, Isle of Man and through the Bay of Biscay. They have occasionally been seen in North Sea.

Threats

There have been regular strandings of common dolphins on the Cornish and Devonshire coasts; these appear to be related to damage from entanglement in fishing gear. As Common dolphins feed on fish species which are also targeted by fisheries, they are attracted to areas where fishing is taking place and are accidentally caught up. Fishing techniques such as purse seine and trawling are particularly dangerous to dolphins. “Dolphin friendly” fishing techniques can cause less damage to dolphin populations however do not exclude them from harm and are not “ecosystem friendly”. They often can cause greater damage to other marine animals including sharks, turtles and birds. Fishing techniques such as pole fishing are more environmentally friendly as they target specific species. Other threats to dolphins include pollution, collisions with vessels, decrease in available prey and habitat degradation. Evidence suggests that seismic sonar emitted by vessels can cause hearing damage; this could impact upon communication, prey and predator detection and navigation.