Aquafacts / Porpoises

Porpoises 

Your questions about harbour porpoises and Dall's porpoises answered at last by our biologists and other reputable sources.

Quick facts

13 years

Average lifespan

3 to 5

Average group size

Hybrid porpoises

Harbour porpoises can breed with Dall's

Herring 

A popular porpoise food

7

Total known number of porpoise species

What is a porpoise?

A porpoise is a member of the order cetacea meaning that it is related to whales and dolphins. Porpoises however, fall into their own category under cetaceans due to differences that set them apart from other whales and dolphins. Porpoises tend to be smaller in size than most dolphins, have a triangular shaped dorsal fin (a dolphins dorsal fin is more crescent shaped), a blunt, rounded snout, and flat "spade" shaped teeth (contrasted with a dolphins cone-shaped teeth). There are seven known species of porpoise in the world including: harbour porpoise, Dall's porpoise, vaquita, spectacled porpoise, Burmeister's porpoise, narrow-ridged finless porpoise, and the Indo-Pacific finless porpoise.

What types of porpoise live in British Columbia?

Two species of porpoise can be found in British Columbia (B.C.) – Harbour porpoise and Dall’s porpoise.

Photo: NOAA

Harbour porpoise

Phocoena phocoena

Photo: NOAA

Dall's Porpoise

Phocoenoides dalli

How can I identify a harbour porpoise?

Harbour porpoise are the smallest cetacean species in B.C. reaching a maximum size of 1.8 m long and 200 lbs. They are recognized by their grey colouring and small, but rotund and stocky body with a small triangular dorsal fin.  Their colouring tends to have a dark grey back which fades into mottled grayish-white sides, and an almost white belly – making the harbour porpoise look like its wearing a black ”cape”. There is a distinct dark line that runs from the corner of their mouth to the top of their pectoral (side) flipper. Males and females usually look the same, although females are slightly larger than males. Harbour porpoise are a very difficult animal to spot and individually identify due to their small dorsal fin, cryptic behaviour, and minimal surface activity.

How can I identify a Dall's porpoise?

Dall’s porpoise are larger than harbour porpoise, reaching a maximum size of 2.2 m long and 350 lbs. They are recognized by their black and white colouring, extremely robust and muscular body, small rounded head, and small triangular dorsal fin with a white tip. During slow dives a large hump located slightly forward of the tail flukes can be detected. Their colouring tends to be basically black on the upper portion with large oval-shaped white sides, and white bellies – leading them to be mistaken for “baby” killer whales. Male and female colouring is the same; however, males are slightly larger, have a stockier body, and more pronounced ventral hump.

Dall’s porpoise are the fastest cetacean in B.C., reaching speeds up to 55 km/hr.  Traveling at quick speeds creates a distinct ‘rooster-tail’ splash.  Dall’s porpoises’ also take delight in bow riding with fast-moving vessels, making them an easier species to spot than harbour porpoise.

Where do porpoises live?

Harbour porpoise have a circumpolar distribution throughout the temperate and boreal waters of the northern hemisphere. Three isolated groups are recognized: north Pacific, north Atlantic, and Black Sea- Sea of Azov. They prefer near coastal waters although occasional sightings in deep water are recorded. They are frequently seen in B.C.’s many inlets and fjords. Infrequently, they may also be spotted in brackish rivers.

Harbour porpoise are thought to remain resident for extended periods in one area.  One of those areas is the waters around Prince Rupert, B.C. where larger than normally observed aggregations can consistently be found. The North Coast Cetacean Research Initiative (an initiative of the Ocean Wise Marine Mammal Research Program) is studying the distribution of harbour porpoise off Prince Rupert Harbour and surrounding areas to evaluate the seasonal and daily patterns of habitat use.

Dall’s porpoise are found only in the North Pacific Ocean and adjacent seas (Bering Sea, Okhotsk Sea, and Sea of Japan). Thought to be primarily an oceanic species, they do occur coastally in some regions including southern B.C. Migration patterns of offshore populations are poorly known; however, many coastal populations, like those in B.C., are year-round residents through-out much of their range, generally moving north for the summer and south for the winter.

What do porpoises eat?

Harbour and Dall’s porpoise feed mainly on small schooling fishes (herring, anchovies, mackerels, and sauries) and cephalopods (octopuses, squid, and cuttlefish).

Harbour porpoises are generally seen in small groups between 2 to 5 animals. Larger congregations of several dozen harbour porpoises are sometimes observed, particularly in spring or fall. These large groups are thought to be feeding on prey that is concentrated by strong, seasonal tides.

Do porpoises interact?

Porpoises are generally seen in small groups between 2 to 10 animals; however, for both species, larger aggregations have been reported in groups that were actively feeding or offshore.

How do porpoises reproduce?

Porpoises are mammals and give birth to live young. Harbour porpoise are often described as promiscuous and polyandrous (males ensure their reproductive success by mating with as many females as possible) with significant sperm competition. Males have a marked seasonal development of the testes, which may weigh up to 6% of their body weight during the mating season. In B.C., mating appears to peak in late summer to early fall. Dall’s porpoises on the other hand have a more polygynous mating system where the males compete for females.  A male Dall’s porpoise will choose and guard a fertile female to ensure a better chance of paternity.

Female porpoises are pregnant for 10 to 12 months and a single calf is usually born during May to September. Nursing may occur for up to 8 to 12 months, but is significantly reduced after the first few months. It is unknown when harbour porpoises reach sexual maturity in the north Pacific, but in the north Atlantic it is around 3-4 years. Females have a calf every 1 to 2 years, and both sexes may live to 13 years.

Hybridization (the interbreeding of two different species) between harbour porpoise and Dall’s porpoise has been discovered in southern B.C. waters with harbour porpoise as the paternal parent and Dall’s porpoise as the maternal parent. These natural hybrids tend to appear more similar to Dall’s porpoise in body shape, diving characteristics, and behaviour, but lack the white side patches with colouring that is more similar to the harbour porpoise.

How long do porpoises live?

8-20 years, though animals older than 10 are rare.

What predators do porpoises face?

In B.C. Bigg’s (mammal-eating) killer whales prey on porpoises. Harbour porpoises are the most frequently reported stranded cetacean in B.C. though reasons for their stranding are various. In many parts of their range, both harbour and Dall’s porpoise populations are heavily impacted by entanglement in fish nets, particularly gillnets. They also appear to be very sensitive to noise and other human impacts in more urban areas.

What threats do porpoises face?

In Canada, harbour porpoises are listed as a species of ‘special concern’. They appear to be particularly sensitive to human activities like fishing (they can become bycatch in nets) and marine noise pollution (by shipping traffic). Porpoise are also affected by contaminants that make their way into the ocean and can contaminate their food sources.

In Canada, Dall’s porpoise are listed ‘not at risk’. The global population is still numerous; however, oceanic populations have been the target of human consumption in Japan, and they are at high risk of fishing bycatch.  Porpoise are also affected by contaminants that make their way into the ocean and can contaminate their food sources.

What can I do to help porpoises?

  • Participate in Citizen Science – Report your porpoise sightings to the B.C. Cetacean Sightings Network using the WhaleReport app. Sightings give valuable information about species distribution patterns and helps in recovery and management planning.
  • Give them space – Make sure to always follow the Be Whale Wise Guidelines when watching porpoises, or visit Whale Trail B.C. locations and observe cetaceans from land – a zero-impact alternative to whale watching.
  • Eat sustainable seafood – Know if your seafood is from a healthy, stable stock, caught by environmentally friendly methods. Choose Ocean Wise Sustainable Seafood.
  • Dispose of waste responsibly – What goes down your drain eventually ends up in the ocean. Dispose of your hazardous waste at designated drop-off sites. Always reduce, reuse, and recycle.
  • Clean our shorelines – Garbage in the ocean poses a risk to all marine life, including porpoises and their prey. Help reduce marine debris by participating in the Great Canadian Shoreline Cleanup.

References

  1. American Cetacean Society. Harbour Porpoise and Dall’s Porpoise Fact Sheets.
  2. Crossman, C.A., Barrett-Lennard, L.G., & Taylor, E.B. (2014). Population structure and intergeneric hybridization in harbour porpoises Phocoena phocoena in British Columbia, Canada.
  3. Fisheries and Ocean Canada. Harbour Porpoise
  4. Ford, John K.B. 2014. Marine Mammals of British Columbia. Victoria: Royal British Columbia Museum.
  5. Porpoise Conservation Society. Harbour Porpoise and Dall’s Porpoise Species Identification
  6. Wild Whales – B.C. Cetacean Sightings Network. Harbour Porpoise and Dall’s Porpoise Species Identification


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