How do I know it is a porpoise?
When we say “whale” or “dolphin”, most people have at least a general ideal of what they area and what they look like. Most people, however, can’t really quite picture a porpoise. And not because they are not awesome, they are! It is just that many aspects of their biology and ecology have kept porpoises hidden, even from scientists, especially species that are found in remote areas. Porpoises are quite small and usually seen alone or in small groups of a few individuals, unlike dolphins who gather in large groups and display many aerial behaviours, which makes them easier to spot. Porpoises seem to be less active on the surface and also tend to shy away from humans.
But our knowledge about them is steadily increasing, especially in the past few years, thanks to technological advances, such as behavioural and satellite tags we can put on them. Currently, the scientific community has recognised just 7 species of porpoises worldwide, all of which belong to the family Phocoenidae. Their closer evolutionary cousins are belugas and narwhals (the unicorns of the seas).
Basically, each porpoise species has its unique looks. Some have a small triangular dorsal fin, some have large ones (check out the Spectacled porpoise!) and others do not even have dorsal fins! So how do we distinguish porpoises?
All about the teeth
It’s all about the teeth. Cetaceans are divided into two main groups: those with teeth (toothed whales) and those without teeth (baleen whales, or "true" whales). Porpoises have teeth, and teeth like no other. Most toothed whales have pointy teeth, but porpoises don’t – they have teeth shaped like a spatula! Their teeth are compressed and rather small, reaching about 1 cm in length.
Unfortunately, they do not go around showing us their teeth, but the species are easy to identify. We look at the shape and size of the dorsal fin, the colouration patterns in the body, and the overall size. It makes our lives easier that their distribution ranges rarely overlap.
Language Common name(s)
Figure of all porpoises (from Whalewatcher-Porpoises-2010.pdf (iucn-csg.org))
The harbour porpoise is the most abundant species. Its scientific name is Phocoena phocoena – phocoena means “pig fish”.
Harbour porpoises are found exclusively in the northern hemisphere. The largest known population is in the North Sea and surrounding waters with an estimated size of nearly 500000 animals, but they are also present in smaller numbers in other areas throughout the North Atlantic and the Pacific. Records in the Mediterranean Sea are scarce, but there is a small population in the Black Sea, with fewer than 1000 animals. The most at-risk population is that of the Baltic Sea, with fewer than 500 animals, listed by the International Union for Conservation of Nature as Critically Endangered.
International conservation efforts are underway for this population (check them out here sambah - Home)