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Harbour porpoise Phocoena phocoena

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One of the smallest cetacean species, harbour porpoises are generally inconspicuous in their behaviour. They are usually found in small groups, and generally surface quickly without showing too much of their body above the water surface1. As such, they are not often the primary target of dolphin watching activities. However, as one of the most common whale or dolphin species in Europe and both coasts of North America, whale watchers in either of these regions have a good chance of catching a glimpse of this compact and enigmatic porpoise.  The porpoises’ nearshore distribution allows them to be observed from land in many places, including the Netherlands, where they are the target of a unique land-based form of whale watching that allows watchers to listen to harbour porpoise vocalisations in real-time (see the ‘harbour porpoise studio’ case study on this site). They can also be observed from the Golden Gate bridge or ferries crossing the San Francisco Bay.

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Not to be confused with: 

Harbour porpoises are fairly distinct from all other species with which they share habitat.  There are no other species of porpoise in the North Atlantic with which they could be confused, and all other cetacean species in the Atlantic are much larger.  In the North Pacific, harbour porpoises share habitat with Dall’s porpoises, and indeed, hybrids are known to occur between the species, usually the result of a Dall’s mother and a harbour porpoise father2. However, in the absence of hybridization Dall’s porpoises can be easily distinguished from harbour porpoises by their striking black and white pattern and the white blaze on the dorsal fin. 

Distribution

There are currently three formally recognised subspecies of harbour porpoises: The Pacific harbour porpoise (Phocoena phocoena vomerina), the Atlantic harbor porpoise, (P. p. phocoena), and the Black Sea Harbor Porpoise (P. p. relicta)3.  A fourth subspecies has been proposed for harbour porpoises found around the Iberian Peninsula and north Africa (P. p. meridionalis).  Throughout its range the species is found in cool temperate or subpolar waters, usually coastal areas and depths of less than 100m.

Native to the following countries: Belgium; Bulgaria; Cabo Verde; Canada; China; Denmark; Estonia; Finland; France; Georgia; Germany; Gibraltar; Iceland; Ireland; Japan; Latvia; Lithuania; Mauritania; Morocco; Netherlands; Norway; Poland; Portugal; Romania; Russian Federation; Senegal; Spain; Sweden; Tunisia; Turkey; Ukraine; United Kingdom; United States

Presence uncertain in: Democratic People's Republic of Korea, Republic of Korea.

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Biology and Ecology

Feeding

Harbour porpoises have a high metabolic rate, so they need to eat often, and rely on prey with high caloric content.  As such, in most areas they predominantly feed on fish species with a high fat content like herring, sprat, anchovies, whiting and sand eels1,4,5.  However, different populations have varying prey preferences. Recently they have been observed to feed on cod off the coast of Greenland 1, and in other areas they are also known to feed on squid and crustaceans1.  Although harbour porpoises normally feed alone or in very small groups, in some cases they have been observed working together to corral or herd fish while feeding1.

Social structure, Reproduction and growth

Harbour porpoises are usually found in small groups of up to five or six individuals1,2,6. However larger (temporary) aggregations have also been observed in some locations.  Gestation lasts 10.5 months, and calves are roughly 70-80cm at birth, weighing only 5 kg7.  Calves are dependent on their mothers for milk until they are roughly a year old, but may start to catch their own prey (e.g. small crustaceans and fish) long before they are fully weaned7.   Both males and females become sexually mature by the age of three or four years, but have very short average life spans of only 8-10 years1,7.  In the Atlantic females can  produce calves every year during their short reproductive phase, but in the Pacific it appears to be more common for them to have calves every other year1.

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