On a semi-covered catamaran, we head out to explore the Salish Sea. The sun shines off the water as we gaze at the snow-capped Olympic Mountains and admire the beauty of the Pacific Northwest. We scan the horizon for blows or dorsal fins, when suddenly a tiny 6-inch grey fin appears, then disappears just as quickly. Not a ripple. We begin to doubt we even saw anything in the first place! Just then we see another dorsal fin appear; the smooth circular motion as it breaks the surface and submerges again is very typical of the smallest cetacean found in BC waters: the elusive harbour porpoise.
There are only seven species of porpoises in the world, and we are lucky enough to find two of them in the Salish Sea! Speedy Dall’s porpoise—often mistaken for baby killer whales—tend to attract much more attention with their dolphin-like behaviour, surfing the bow waves or wakes of boats. Tiny harbour porpoise, on the other hand, are much more shy.
Measuring in under 6.5 feet long and 120 pounds, these small cetaceans don’t like to draw attention to themselves. A favourite snack of Bigg’s (aka transient) killer whales, they aren’t fast enough to outswim their predators like a Dall’s porpoise (both killer whales and Dall’s porpoise can reach speeds of 55km/hr), nor do they have any means of defense (like the claws of a massive Steller sea lion). Their best defense is simply to hide.
Now think about the world in which cetaceans live; it is a world of sound. Porpoise clicks used for echolocation and communication are shorter and much higher frequency than most other whales, around 130 kHz. Humans can hear up to 20 kHz, and incidentally, killer whales can hear up to about 100 kHz but not much past that. You see where this is going—porpoises have evolved to be ultrasonic to avoid detection by their predators who hear in a more sonic range. Evolution for the win!
What they lack in size, harbour porpoise make up in breeding prowess. During the mating season, females will mate with several different males. Part of the reproductive strategy of these small cetaceans is sperm competition—the male that produces the most has a better chance of passing on his genes. More sperm plus more mating opportunities equals more babies! This has resulted in a marked increase in the size of the males’ testes during the breeding season— up to 4–6% of their total body mass! Now that’s a claim to fame!
Harbour porpoise are usually found in coastal waters less than 100 feet deep. Feeding on small schooling fish like herring, sand lance, and hake, harbour porpoise will catch a fish, turn it around so it’s facing head-first (you don’t want those getting caught in your throat!), and swallow it whole like a little vacuum—1, 2, 3, gulp! Stranded harbour porpoise have been found with several fish neatly lined up in their digestive tracts head to tail.
Spending your life in nearshore waters usually means increased interactions with humans, from pollution to increased vessel traffic. These small porpoise are particularly vulnerable to entanglement in drift nets and gill nets. The Pacific population of harbour porpoise is listed as Special Concern under the Species at Risk Act.
Harbour porpoise make a very distinct “pfff” sound when they surface quickly to exhale and inhale, leading to their nickname of “puffing pig” on the east coast of Canada. The name “porpoise” itself comes from several older languages meaning “sea swine.”
If the weather is calm, you can spot harbour porpoise from shore in many areas around Victoria! Island View Beach, Oak Bay, even Patricia Bay looking into the Saanich Inlet are great places to look for porpoise. Jordan River, west of Victoria, and East Point on Saturna Island are great viewing spots too. Bring your binoculars if you want a closer look, but scan with your naked eye to cover more water and then use the binoculars once you’ve spotted them. As soon as the wind picks up, though, you’ll lose sight of those tiny fins in the ripples.
While harbour porpoise can be seen around the Salish Sea year-round (that is, if you can spot them in the blustery winter weather!), they use the area differentially depending on the season. Sightings are much higher throughout the area from April to October, coinciding with the breeding season. Two important feeding areas are found near Discovery Island and Race Rocks Ecological Reserve, the use of which is affected by both the tides and the lunar cycles. An important reproductive area has also been identified in eastern Juan de Fuca Strait.
If they were in high school, Dall’s porpoise would be part of the football team—loud, boisterous, and you always know when they’re in the area! Harbour porpoise would members of the math club—quieter and less obtrusive perhaps, but nonetheless fascinating and clever, and a very important part of this diverse ecosystem! So the next time you look out at the water and notice those tiny dorsal fins—often visible from shore on calm days—don’t write them off as “just a harbour porpoise;” remember these are also known as the world’s greatest small cetaceans!