Deep dive...into Harbour porpoises

Compared to other porpoises and their dolphin cousins, the harbour porpoise is relatively small. The species has a rounded head with no beak and distinctive spade-shaped teeth.   

Its body is robust and stocky, and colouring is dark brown on the back and a paler grey or white underneath that blends in half way along its sides. It also has a small dorsal fin just past the centre of its back.  

The harbour porpoise gets its name because it is usually found close to shore in shallow waters (hence the ‘harbour’ part). The word porpoise comes from an unflattering source – it is the Latin word for pig.  

The harbour porpoise does emit a sneeze-like puffing sound when it breathes, not unlike a pig’s snort! They are sometimes called by a nickname, ‘puffing pig’.  

Four subspecies of harbour porpoise have been recorded: one in the North Atlantic, one in the eastern Northern Pacific, another in the Black Sea and one more in the western North Pacific. A further subspecies has been proposed for harbour porpoises living around the Iberian peninsula and north Africa.  

The species is a little shy but is very active and needs to feed continuously to provide the energy needed for its speedy swimming. Harbour porpoises are often spotted on their own in small groups (most commonly a mother and calf group). They tend to surface quickly and don’t show much of their body above the water.

On average, they weigh in around 55-70 kilograms and measure around 1.5 to 2 metres in length. Their average lifespan is 20 years, a little shorter than some other porpoises and dolphins.

As mentioned, there are four subspecies of harbour porpoise located in different oceans and seas around the world. Generally, though, most of them are found in the North Atlantic and North Pacific. 

They are usually spotted visiting estuaries, shallow bays and tide channels though they are also observed swimming up rivers from time to time.  

Their global population is estimated at over a million individuals. They are classified as Least Concern on the IUCN Red List of Threatened Species. However, there are concerns about the Black Sea population (listed as Endangered) and also the population around the Iberian peninsula.

Check out this underwater footage of curious harbour porpoises:  

Harbour porpoises have a high metabolism. They need to eat often and to take in calorie rich prey such as herring, anchovies, whiting, sprat and sand eels. They also seek out squid and octopus when they can. 

One of the main threats to harbour porpoises is, unsurprisingly, entanglement in fishing gear. This can go on to cause injury, fatigue, compromised feeding, and sometimes even death.

Harbour porpoises are at risk of vessel strikes throughout their range but the threat is higher in areas with busy ship traffic.

Climate change and pollution are a threat to all whales and dolphins because of the loss of habitat as waters become warmer.

Plastics and micro plastics, along with chemical pollutants, entering into the water system are a serious threat to all creatures in our ocean.

Harbour porpoises, like other cetaceans, use noise to communicate and to locate prey. Increased noise pollution from vessels and other human activity interferes with this ability. 

Harbour porpoises are hunted off the coasts of Greenland and South Korea, as well as in several other countries around the world.