Harbour porpoises: Nine surprising things about the world’s greatest small cetacean!
There are only seven species of porpoise in the world, and we’re lucky enough to have two of them here in the Salish Sea!
There’s the speedy and flamboyant Dall’s porpoise which likes to surf the bow waves of boats and grab all the attention. It’s hard not to get excited when you see these little black and white torpedoes in action.
Their tiny harbour porpoise cousins, on the other hand, are much more demure. They don’t come with the flashy black and white packaging. And there’s none of that bow-riding nonsense for them. They don’t want to be seen. But that’s okay. Harbour porpoises are fascinating in their own way. Read on to learn eight fun facts about the Salish Sea resident we fondly refer to as the world’s greatest small cetacean!
1. They’re the size of a small adult human
At only two metres (6.5 ft.) long and 60 kg (120 lb.) maximum, these small, grey cetaceans don’t like to draw attention to themselves. They’re a favourite snack of Bigg’s (transient) killer whales and aren’t fast enough to outswim them. Nor do they have any means of defence, such as claws or massive teeth. Their best defence, quite simply, is to hide.
2. They’re known as “puffing pigs”
Harbour porpoises make a very distinct “pffff” sound when they quickly exhale and inhale at the surface. This led to their nickname of “puffing pig” in Atlantic Canada. The name “porpoise” itself comes from several older languages meaning “sea swine.”
3. They’re ultrasonic
Cetaceans live in a world of sound. Being quiet can help them avoid predators like killer whales. As a result, porpoises have evolved to be ultrasonic. The clicks they use for echolocation and communication are shorter and much higher frequency than most other whales, at around 130 kHz. For comparison, humans can hear up to 20 kHz, and killer whales can hear up to about 100 kHz but not much past that. Evolution for the win! This is one of the differences between dolphins (such as killer whales) and porpoises—dolphins are sonic, whereas porpoises are ultrasonic.
4. They’re meticulous eaters
Harbour porpoise are usually found in nearshore waters with a depth of less than 100 feet. They feed on small schooling fish like herring, sandlance, and hake. Once they catch a fish, they turn it around so it’s facing head-first (so the scales don’t get caught in their throat) and swallow it whole like a little hoover—1, 2, 3, gulp! Stranded harbour porpoises have been found with several fish neatly lined up head to tail in their digestive tracts!
5. They have an, um, interesting claim to fame
What they lack in size, harbour porpoises make up in breeding prowess. During the mating season, it’s pretty much a free-for-all with females mating with several different males. Part of their reproductive strategy involves 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 their testes during the breeding season — around 4–6% of their total body mass! Now that’s impressive!
6. They’re very susceptible to human disturbance
Hanging out in coastal waters usually means increased interactions with humans, from pollution to increased vessel traffic. These small porpoises are particularly vulnerable to driftnet and gillnet fisheries through entanglement. The Pacific harbour porpoise population is listed as Special Concern under Canada’s Species at Risk Act.
7. They can be spotted from shore
On a calm day, harbour porpoises can be seen from shore in many areas around Victoria! Island View Beach, Oak Bay, Patricia Bay looking into Saanich Inlet and even East Point on Saturna Island are great places to look for them. 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, those tiny fins will disappear into the ripples.
8. They’re seasonal
Harbour porpoises can be seen around the Salish Sea year-round—that is, if you can spot them! But they prefer different areas at different times of year. Sightings are much higher throughout our region from April to October. This coincides with the breeding season. Two important feeding areas have been identified, near Discovery Island and Race Rocks Ecological Reserve. The use of these areas is affected by the tides and the lunar cycles. An important reproductive area has also been identified in eastern Juan de Fuca Strait.
9. They’re the strong silent type
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 be part of the math club—quieter and less obtrusive, 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 see those tiny dorsal fins—often visible from shore on calm days—don’t write them off as “just a harbour porpoise.” Remember, these are the world’s greatest small cetaceans!
To learn more about harbour porpoises and the other fascinating animals we see on our tours, join us for a whale and wildlife adventure today! (Link…)