British Mammals - Cetaceans Content from the guide to life, the universe and everything

British Mammals - Cetaceans

0 Conversations

The shield of Science, Mathematics and Engineering faculty of the h2g2 University.

British Mammals
Artiodactyls | Carnivora | Cetacea | Chiroptera | Insectivora | Lagomorpha | Pinnipeda | Rodentia | Mammal Surveying

It is very difficult to come up with a comprehensive list of 'native' cetaceans, the whales and dolphins. There are some that are frequently found in the waters off the UK, some that are less common and others that turn up once in a while; over 20 species have been recorded altogether in UK waters. There is no easy place to draw a line between resident species and visitors, so for the purposes of this Entry we will include those cetaceans that could be expected to be seen from the shores of the UK.

Cetaceans are split into two suborders: the baleen whales, which feed by filtering the water and digesting the organisms in it; and the toothed whales, which, as the name suggests, have teeth.

Baleen Whales (Mysticeti)

These whales have 'baleen plates' attached to their upper jawbones. Looking like large, hairy combs arranged in two parallel rows, they are very effective in filtering organisms from the water. The whale opens its mouth, allowing sea-water to flood in, then squeezes the water against the plates with its tongue, trapping plankton in the fibres. This is so effective that the blue whale, which feeds in this way, is the largest animal ever to have appeared on Earth! The plates are made out of keratin, one of nature's strongest biological substances. Made out of tough, fibrous protein strands, keratin is also appears in nature as the claws in other mammals and as fingernails in humans.

Though there are quite a few baleen whales that visit the UK occasionally, there is only one that could be considered to be native, the minke whale. Other baleens that can be seen include the sei, fin, northern right whale and even the spectacular humpback whale; but all of these prefer much deeper water than can be found around the British Isles and sightings from shore are extremely rare.

Minke Whale Balaenoptera acutorostrata

Found mainly on the Atlantic coast of Britain and Ireland and the North Sea as far south as Yorkshire, minke whales seem unsure whether to be gregarious or not. They spend most of their lives alone or living in a pair, shunning others of their species, but will quite happily mingle with large groups of other cetaceans and will often approach and swim alongside boats. They also have an inconspicuous track through the water, but occasionally blow their cover by lunging above the surface, fully exposing their head. Unless they do come close, they can be tricky to identify as their triangular heads are not often exposed, and the only other way to identify them beyond doubt is by the white band on their flippers. Minke whales grow to around 7-8½m in length.

Toothed Whales (Odontoceti)

With the exception of the sperm whale, toothed whales are smaller than their baleen counterparts, meaning more of them can be found in the shallow waters around the UK. There are some important differences between the two suborders:

  • Toothed whales have one blowhole on top of their heads, whereas baleen have two.

  • Toothed whales have evolved echolocation, which helps them find their food. The whale sends out a series of clicks and is able to accurately judge how far away objects are by the length of time it takes the echo to return.

  • Toothed whales tend to be much more social than baleens, forming 'schools' or 'pods' up to a dozen individuals strong. Occasionally, these groups merge into 'superpods'. One such group of thousands of dolphins gathered off the Cornish coast in January, 2004, attracted by large shoals of mackerel.

The toothed whales described in this Entry are dolphins, cetaceans in the family Delphinidae, with the exception of the harbour porpoise, which belongs to the family Phocoenidae. Note that 'dolphin' and 'porpoise' are not interchangeable, as many people believe! Other toothed whales that occur in British waters include the sperm whale, long-finned pilot whale (actually a dolphin!) and a few species of beaked whale, but sightings from shore of these species are very rare indeed.

Harbour porpoise Phocoena phocoena

This is the smallest and most common of Britain's cetaceans. When fully grown it is similar in size to a human adult and the North Sea population alone is estimated to be around 280,000 individuals1. As you would imagine by its name, it prefers to stay close to shallow waters around the coast, and regularly inhabits estuaries and fishing ports. That is not to say that it is an unadventurous creature; it has been spotted hundreds of miles from the shore. It is a fairly common sight, and is fairly easily identifiable by its small fin and blunt, beakless head.

Although it is not under any conservation threat, concerns have been raised over the numbers of porpoises caught in fishermen's gillnets. These are a type of net that has a wide opening which encourages fish to swim through, but the gap proves not quite wide enough and the fish becomes stuck by its gills as it tries to reverse out. Although porpoises, being mammals, do not have gills, they are frequently caught up in them despite the fact that their echolocation is good enough to detect their presence. It may be that curiosity literally kills the porpoise. Gillnets are now banned in international waters.

Common bottlenose dolphin Tursiops truncates

The most common and well-known dolphin is usually found on the Atlantic coast of Britain and Ireland, with a few making their way further up the English Channel and into the North Sea. Cardigan Bay in Wales also supports significant populations. If you see a photo of a dolphin leaping out of the water, surfing behind the stern of a boat or performing in a waterpark, it's more than likely it's a bottlenose.

Interestingly, there are significant differences between bottlenose dolphins in UK waters and those off, for example, Florida. Those living in colder water are much larger (4m in length as opposed to 2½m), have much greater fat reserves and are better adapted for diving to depths. There is much debate over whether the differences are enough for the two to be considered separate species.

Risso's dolphin Grampus griseus

These are predominantly found off the Scottish, Welsh and Irish coasts, but they occasionally make their way further south. They are a fairly distinctive grey colour, becoming whiter with age, and have a very prominent curved fin. They are quite rare around the UK, but are sometimes found close to shore in the summer months.

Short-beaked common dolphin Delphinus delphis

In the mid-1990s, one species of common dolphin was divided into two; the short- and long-beaked, and a third may soon be categorised in the Red Sea. Only the former is found in the north Atlantic, and is common in the south-west of England, Wales and Ireland. There are also populations to the west of Scotland and even as far north as the Hebrides, but few beyond Devon in the English Channel and only occasional sightings in the North Sea. It commonly breaches the surface of the water, exposing its tan-patterned flanks, and is a very sociable dolphin with an average pod size around the UK of 14 individuals.

White-beaked dolphin Lagenorhynchus albirostris

If you're in the north of England or Scotland, this is probably the dolphin you're most likely to see. It is quite a slow mover, being fairly bulky, giving watchers time to try to pick out its pale 'saddle' behind its dorsal fin. This is its most readily identifiable feature; unless it breaches the surface, you're unlikely to catch sight of the beak that gives it its name. It can often be seen around boats.

Atlantic white-sided dolphin Lagenorhynchus acutus

Superficially similar to the white-beaked dolphin in size and colour, the white-sided dolphin lacks the back saddle of its cousin. Extremely gregarious, its normal pod size comprises anything from two to 15 dolphins, but groups congregate much more frequently than other species, and groups numbering up to a thousand are not uncommon. Other species will often be found in these large groups. The dolphin is a powerful swimmer, and has been observed cruising for several hours at an impressive 14km/hour (ten miles per hour). It is very much a deep water dolphin, but is occasionally recorded in summer months from the land.

Killer whale Orcinus orca

This is the largest of the dolphins, with males reaching up to 10m in length. They are, at birth, bigger than most common dolphins! It may come as a surprise that, apart from humans, no other creature is as widely distributed around the world. They are distinctively white and black in patches, and have a large dorsal fin that protrudes high above the water when surfacing. Although in the UK they are normally seen around the west coast of Scotland and Orkney Islands, records exist from a wide variety of places, including Pembrokeshire in south-west Wales, Kerry and Cork in Ireland and in the northern reaches of the North Sea.

The sheer size and beauty of killer whales has led them to make great film stars; Orca and Namu were the stars of films in the 1960s and 1970s, and who can forget Keiko, the star of Free Willy?

Watching Cetaceans From the Shore

The best places to go to watch whales are the Western Isles of Scotland, as the narrow channel that separates them from Skye and the mainland (known as the Minch) attracts a large number of species – including most of those mentioned here that are not considered resident. The North Channel, between Scotland and Northern Ireland, is also a good place, as is Cardigan Bay in Wales. If you can't get to one of these places, the best bet is to find a good, high vantage point overlooking the sea; arm yourself with a clear day, a pair of binoculars or a telescope and a large amount of patience. On their excellent How To Watch page, the Sea watch Foundation has this to say about watching cetaceans:

We recommend two- to four-hour watches because they provide a compromise between the minimum length of time that is worth watching for (one hour) and the ideal length of time to maximise chances of seeing a cetacean (around five hours).

If you're really serious about cetaceans, Seawatch organise regular surveys, from shore and sea, and their website is a great source of more information. The Joint Nature Conservation Committee, who advise the Government on conservation issues, have also published a cetacean atlas, which provides plenty of information about specific species.

1This figure is not for the UK alone, and is quoted to give readers an idea of just how common the harbour porpoise is.

Bookmark on your Personal Space

Conversations About This Entry

There are no Conversations for this Entry

Edited Entry


Infinite Improbability Drive

Infinite Improbability Drive

Read a random Edited Entry

Categorised In:

Written by

Write an Entry

"The Hitchhiker's Guide to the Galaxy is a wholly remarkable book. It has been compiled and recompiled many times and under many different editorships. It contains contributions from countless numbers of travellers and researchers."

Write an entry
Read more