Ireland's Biodiversity Awareness Campaign

Harbour Porpoise – Muc Mhara – Phocoena phocoena

Harbour Porpoises are one of the most common cetaceans (large sea dwelling mammals) in the Irish waters and sitings are particularly frequent at this time of year.

Physical description

Harbour porpoises have a small rounded head with no distinct beak and are smaller than dolphins, with adults typically ranging between 1.5 – 1.9 metres long. They have a dark grey back with a small triangular dorsal fin. Their underside is pale with white extending up the sides of their body beneath their fin.

Picture courtesy of Randal Counihan Irish Whale & Dolphin Group

Surfacing behaviour

Harbour porpoises behave differently to their exhibitionist dolphin cousins. They are more shy creatures, coming up to the surface only to breathe rather than to play and so, can be quite difficult to spot. They normally surface briefly, 3-4 times in a row, rarely lifting their body out of the water, before diving down for up to 8 minutes. Harbour porpoises are sometimes referred to as ‘puffing pigs’ (the Irish name means sea pig) due to the noise that comes from their blow holes!

Spotting Porpoises

Harbour porpoises are often found in small, scattered groups of up to 8 individuals but are more commonly seen swimming alone chasing or searching for the small fish they feed on. They tend to stay close to land year-round, although some have been seen up to 200 km out at sea. Mothers are seen with their calves between March and May but very little is known about when and where they give birth. The best place to spot porpoises is off headlands and bays, especially from June through to autumn / winter. Sitings of diving gannets and feeding seabirds will sometimes indicate the presence of porpoises feeding on schools of fish.

Watch out for brief glimpses of a small dark back and triangular fin rolling through the water surface. Their heads and tails rarely show, and because of their slow movement, they do not produce splashes which are more typical of dolphins. Porpoises usually tend to avoid boats and do not bow ride in the way that dolphins do.

Picture courtesy of Simon Berrow, Irish Whale & Dolphin Group

Conservation Issues

There are many threats to this animal. One of the most common threats is the danger of getting caught in fishing nets and trawls Pollution and habitat disturbance/destruction are also key threats to Harbour porpoises. Because of their threatened status in European waters, harbour porpoises are listed on the Annex II of the EU Habitats Directive and Ireland is required to designate Special Areas of Conservation to protect them (LINK to the directive)



! Did you know that 24 species of whale, dolphin and porpoise have been recorded in the Irish waters !

Check out the Irish Whale and Dolphin Group  (IWDG) website for more information on Irish cetaceans. This website contains a wealth of information including species profiles, spotters guidelines, information on where to go to spot common species and listings of IWDG courses.

©2007 Department of the Environment, Heritage and Local Government