The Atlantic white-sided dolphin was only recognized as a separate species in 1846. Earlier finds remain unclear because they were sometimes confused with bottlenose (Tursiops truncatus) or common dolphins (Delphinus spp.).

Atlantic white-sided dolphin © M. Camm

Physical Description & Behaviour

Atlantic white-sided dolphins are large and robust animals with a short thick snout grading smoothly into the forehead and a tall curved dorsal fin. They are more colourful than most other dolphins: the back, flippers, fluke and the dorsal fin are black, the sides are lighter grey and a white patch on the side extends from below the dorsal fin and continues toward the tail. The thick tailstock has a striking yellow band. Males can reach a maximum body length of 2.7 metres and a weight of 230 kg.

The number of dolphins observed in a group varies from a few individuals up to several hundred but typical inshore groups around the British Isles contain less than 10 individuals.

Atlantic white-sided dolphins feed opportunistically on schooling fish (herring, mackerel, smelt and gadid fish as well as squid). Recent analyses of stomach contents indicate that their prey varies depending on their location and the time of year.

Distribution & Abundance

Atlantic white-sided dolphins inhabit the cold-tempered North Atlantic. Conducting censuses of oceanic dolphins is really challenging, requiring extensive surveys. Estimates for the western Atlantic total about 40,000 individuals, including the northern part of the North Sea.

IUCN Red List of Threatened Species™ Assessment

• LC (least concern) 2023

Threats

Incidental entanglement in fishing gear occurs regularly in mid-water and pelagic trawl nets. Pollution and underwater noise are of additional concern.  The species is currently hunted in the Faroe Islands and in parts of eastern Canada and Greenland.  Historically many were killed in fisheries in Norway, Newfoundland, Greenland, and the Faroe Islands.