Whale of the Month - White-Beaked Dolphin

Species fact file

Common names: white-beaked dolphin

Icelandic name: hnýðingur, blettahnýðir

Scientific name: Lagenorhychus albirostris

Family: Delphiniidae (dolphins)

Max length: 3.1m

Distribution: Temperate and subpolar North Atlantic

‍

White-beaked dolphins have the most northerly distribution of almost any dolphin, and they are well built for cold temperate regions, with a robust body that can be up to 30% blubber by mass. They are dark grey in colour with lighter patches behind the dorsal fin and along the flank. This complex colouration changes gradually with age, so that calves, juveniles, and adults all have quite different colour patterns.

The most distinctive feature of this species is the light grey or white beak, and this is generally the easiest way to tell apart the white-beaked dolphin from the Atlantic white-sided dolphin. Although the white-sided dolphin is an oceanic species and not so frequently sighted in coastal waters, these two dolphins have a broadly similar range and colouration, so they can be easily confused. White-beaked dolphins prefer waters less than 200m deep and are generally found over the continental shelf.

We have only a few estimates of white-beaked dolphin population size. They probably number around one hundred thousand throughout the North Atlantic, with several tens of thousands in Icelandic waters. They are by far the most common species of dolphin in Iceland and are present here throughout the entire year. White-beaked dolphin are one of the four species of cetaceans most frequently encountered on whale watching tours from Reykjavík.

White-beaked dolphins feed on a wide range of prey – from small schooling fishes like herring to larger gadoids like cod, haddock and whiting. Their preference varies across their range, depending on the local abundance of different species. Danish white-beaked dolphins, for example, mainly feed on cod. Harbour porpoises in this region hunt cod, too, but the dolphins typically take larger fish than the porpoises which prevents the two species coming into competition over prey. As well as fish, cephalopods (squid and octopus) are important prey items for white-beaked dolphins in Scotland; here in Iceland, cephalopods do make up a small part of the dolphins’ diet but sandeel, capelin and herring appear to be the main prey species.

It is rare for white-beaked dolphins to become prey themselves, but in Iceland killer whales have been seen hunting dolphins. At present, we’re still not sure how common this behaviour is: the resident population of killer whales seem to mainly feed on herring, so white-beaked dolphins are probably not major component of their diet. Nonetheless, killer whales are enough of a potential threat that white-beaked dolphins have been observed fleeing from them in multiple locations throughout the North Atlantic.  

In Iceland, white-beaked dolphin pods tend to be made up of ten animals or less, but they can be much larger – although the largest pods are generally seen in more offshore regions. Little is known about their social structure. Research carried out in Icelandic waters suggests that white-beaked dolphins have a so called ‘fission-fusion’ society, where individuals form a combination of random short-term and strong long-lasting social bonds with other dolphins. This kind of social structure is similar to what has been observed in many other dolphin populations around the world.

White-beaked dolphins are an acrobatic species and often approach boats to bow ride. They are known to form mixed-species associations with other dolphin species, particularly Atlantic white-sided dolphins, and will occasionally feed alongside larger baleen whales, too; in Iceland, white-beaked dolphins and humpback whales have been observed feeding together.

From satellite tags and photo identification, it seems that white-beaked dolphins in Iceland have quite large ranges and spend a lot of their time travelling. Some dolphins have been photographed in Faxaflói, in the south west, and then resighted much further north. A tagged male dolphin travelled more than 5000km over the course of the 7 months he was tracked, suggesting that the home range of this population could comfortably encompass the whole of Iceland’s west coast as well as part of the north and south coasts.

‍

Learn more about...

How body colouration in white-beaked dolphins changes with age

Using satellite tags to track long term movements and diving behaviour of white-beaked dolphins