HARBOR PORPOISE BIOLOGY
fast facts

Harbor Porpoise

Common name
Harbor porpoise. Also known as: herring hog, sea pig and common porpoise.
Scientific name
Phocoena phocoena
Body size
1.4-1.9 m, 45-60 kg
Average life expectancy
8-12 years
Vocal behavior
Harbor porpoise can emit a very broad frequency range (40 Hz to at least 150 kHz) of sounds. Some are within our hearing range (sonic) and others are above the frequency range that humans can hear (ultrasonic)Use slow repeated echolocation clicks for navigation and rapid bursts of echolocation to focus in on prey or other items of interest.Have also been reported to use whistles, which may have social or communication significance.
Physical characteristics
Are grayish- brown on their backs and sides, with white undersides. There are often gray stripes or flecks within the white pigmentation, especially in the throat region.A distinctive lateral grey – brown stripe extends from the corner of the mouth to the anterior insertion of the pectoral flipper on both sides of the animal. The width and pigmentation of this stripe varies among individuals, however is rarely visible on wild, healthy animals.
Behavior
Harbor porpoise surface with a gentle rolling motion and infrequently breach or display at the surface, although when feeding in tide lines, they will often fast-surface creating a low splash. Unlike Dall’s porpoise, harbor porpoise rarely approach vessels that are underway, however, the harbor porpoise of southern British Columbia have been observed to occasionally exhibit vessel curiosity, especially when clustered in large aggregations. During these aggregations, they have been observed to “surf” in the vessels stern wake.
Distribution
The harbor porpoise has a Northern Hemisphere, circumpolar distribution and is found in the Pacific and Atlantic Oceans, and in the Black Sea and Sea of Azov. This species inhabits the cold-temperate, sub-arctic neritic waters of North America, the Russian Federation and Eurasia; as well as some mid North Atlantic landmasses, such as the Faeroe Islands, Greenland and Iceland. They are typically found in coastal ocean waters, although they have been reported to swim up rivers while pursuing prey.
Diet
Often overlaps with species that are commercially important to humans.A variety of small fish, such as herring, hake, codfishes, and also on small squid (cephalopod). Pacific cephalopod prey species include the market squid or opal squid, also known as calamari.
Foraging behavior
Harbor porpoise feed on prey both within the water column and on the sea floor. They typically eat fish and squid between 10 – 25 centimeters in length. Like other odontocetes, they cannot chew, so they must swallow their prey in whole pieces. It has been proposed, that harbor porpoise may go for larger fish, but will attack them from behind and bite through them at the gills, ingesting the body without the head. Experiments at the Harderwijk rehabilitation center for stranded harbor porpoise in the Netherlands have shown that harbor porpoise actually create negative pressure in their mouths, using their tongues, to suck the fish into their mouths. This would reduce the likelihood that a live fish could escape. They also manipulate fish to swallow them headfirst. Some harbor porpoise have died by trying to eat prey that is too large to swallow.
Habitat
Are coastal species that are typically found in relatively shallow waters to about 150 metres. However, there are sightings of harbor porpoise in much deeper areas. In Georgia Strait, harbor porpoise have been observed in waters over 400 m deep.
Reproduction
Harbor porpoise give birth to one calf every year to every other year after a 10-11 month gestation period. Lactation lasts for approximately 9 months but calves will start to consume solid food at about 5 months of age. Calves may stay with their mothers for up to another 9 months post-weaning. Groups of 2 –3 animals are very common in British Columbia. It is possible that these groups are mothers with their growing calves. Reproduction is thought to be based on sperm competition, rather than competition between males for females. This is because the testes of a male harbor porpoise are exceptionally large during the reproductive season and may account for 4-6% of his body weight. This means that a 50kg male, will have approximately 2 kg testes!
Conservation status
Under Canada’s Species At Risk Act, the harbor porpoise is classified as a species of Special Concern in both the Atlantic and Pacific Oceans. The harbor porpoise is considered particularly sensitive to human activities.