Deep dive…into Atlantic white-sided dolphins

A highly sociable species, the Atlantic white-sided dolphin is often spotted in large pods containing hundreds of dolphins.  

Its name comes from a distinctive white stripe on its side, which begins just below the dorsal fin and turns into a yellow/ochre stripe that continues towards the flukes. The rest of their colouration is grey and they measure up to 2.8 metres in length.

Atlantic white-sided dolphins are quite stocky with a relatively large dorsal fin and short beaks (with a dark upper and white lower lip). They also have a distinctive black eye ring that extends as a thin line to their upper jaw. Also from this eye ring, a thin line goes to their external ear.  

Whilst some other dolphins like to show off, this species is a little more shy overall. They can be seen performing breaches and impressive leaps, tail slapping, and are occasionally spotted bow-riding boats.

They’re nimble swimmers and are sociable with other species, often seen with white-beaked dolphins, bottlenose dolphins, pilot whales and even larger cetaceans such as humpback whales and fin whales.

These dolphins are found in both temperate and cold waters of the North Atlantic Ocean, usually on the edge of the continental shelf and in canyon waters. As they favour deeper water, they aren’t seen close to the shore that often.   

It’s thought that their habitat changes slightly depending on the distribution of their prey species.  

Coasts around the world where they are spotted include the U.S. and Canadian east coasts, Ireland, the UK, Iceland, Norway and East Greenland.  

Atlantic white-sided dolphins eat a variety of prey including herring, cod, mackerel, shrimp, hake and squid. They work together as a group to herd fish into larger groupings where they can be picked off easily.  

They are sometimes spotted scavenging near fishing trawlers or around where whale species are feeding. On average, their dives last less than a minute but there have been individuals spotted holding their breath for almost five minutes.

Getting caught up in fishing fear is one of the main threats to Atlantic white-sided dolphins. They are particularly susceptible to becoming entangled in fishing boat’s mid-water trawls.  

Entanglement can go on to cause injury, fatigue, comprised feeding and sometimes even death. 

Atlantic white-sided dolphins, like other cetaceans, use noise to communicate and to locate prey. Increased noise pollution from vessels and other human activity interferes with this ability.  

Climate change and pollution are a threat to all whales and dolphins because of the loss of habitat as waters become warmer.

Plastics and micro plastics, along with chemical pollutants, entering into the water system are a serious threat to all creatures in our ocean.  

Atlantic white-sided dolphins are hunted in the Faroe Islands and Greenland. In September 2024, 130 individuals were slaughtered during a grindadráp in the Faroe Islands.  

You can read more about it in this article from OceanCare, which also mentions a large kill in 2021 when 1,400 Atlantic white-sided dolphins were killed in one day.