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Harbour porpoise – Mhug mhara - Llamhidydd harbwr – Phocoena phocoena

How to identify

The Harbour porpoise (Phocoena phocoena) is much smaller than any other cetacean found in Welsh and Irish waters. They only reach up to 2 metres in length and usually surface quickly in a rolling motion, not breaching in the way that other dolphins do. Their dorsal fin is also much less prominent, being more triangular in shape. Sometimes they are referred to as ‘puffing pigs’, which originates from the sound of their blow (exhale). When they surface, that ‘puff’ can be heard from shore in very calm conditions.

Fast and rolling motion of a harbour porpoise in Kenmare Bay, Iveragh – Christina Winkler

Ecology, social dynamics and seasonality

Unlike their larger relatives, the dolphins, porpoises live more of a solitary lifestyle and large pods are not a common sight. It is more likely to witness them alone, in small groups of a few individuals, or as a mother and calf pairing. They are the most common species of cetacean in Welsh waters and can be seen almost anywhere, however, they do prefer areas where different currents mix and race, such as around headlands. These areas are where a lot of their favoured prey items like Sand Eel and other smaller fish species congregate. During the summer months, they can be seen more frequently, as they tend to migrate with their food source, which moves to more open water in the colder months. Besides waters around Ireland and the UK, their mainly coastal distribution reaches as far north as Iceland, Greenland and Alaska and as far south as the north of the USA, the north-west of Africa and Japan. Being widely distributed through Europe, they however do not inhabit the Mediterranean Sea and are completely absent in the southern hemisphere.

Spot the porpoise! A pair of harbour porpoises, small and elusive, hard to spot even on a calm day – Christina Winkler
Harbour porpoises around Pen Llŷn

The Welsh Coast Path around the Llŷn Peninsula offers ample viewing points with a good field of view. Another location to see harbour porpoises regularly (as well as Risso’s dolphins) is Bardsey Island.

Harbour porpoises along the Iveragh coast

Even though the most sighted cetacean in Irish waters, harbour porpoises can be hard to spot in rough weather, which we see quite frequently on the west coast of Ireland. Where they have been seen frequently are therefore sheltered bays, e.g. Ballinskelligs and Kenmare Bay, but also off Bolus and Bray Head.


Did you know…

… you can become a citizen scientist yourself and help identify where on Iveragh and Llŷn whales, dolphins and porpoises can be seen?

Iveragh Peninsula

The LIVE Project are partnering with the Irish Whale and Dolphin Group (IWDG) to record sightings of cetaceans along the Iveragh coast. Simply go to the IWDG website to log your sighting, and mention the LIVE Project after your name eg Suzie Smith LIVE Project

Download our handy guide here:

Download PDF • 169KB

Pen Llŷn

For sightings on Llŷn, a form can be filled out through the Sea Watch Foundation, strandings are reported through the CSIP, and for live strandings please contact the British Divers Marine Life Rescue on 01825 765546.


Additional readings:

Species - IWDG


Species - JNCC

Shannon Dolphin ProjectIWDG

Dolphin Watch - Pen Llŷn a’r Sarnau

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