They’re exasperating, those creatures that flit across the path or in the wake of boats, leaping and diving so fast we barely see them. Usually the non-expert isn’t close enough to tell apart the harbour porpoise, Dall’s porpoise and Pacific white-sided dolphin. These speedy small cetaceans seem to have nothing to do in life but cavort, feast and have fun.
Their colouration is similar, and we glimpse only a black, white and grey blur as they hyperactively leap about. Had we time to look closely we could see a white-tipped fin on the back of the Dall’s which distinguishes it from the harbour porpoise. Or was it the more rare Pacific white-sided dolphin we saw? This cetacean is larger than a porpoise, but unless they’re side by side it’s hard to tell how large is “larger”.
“Porpoise” comes from “porcus piscus”, or pig-fish as the ancient Romans called it. Linnaeus, father of species classification, gave porpoises the name Delphinus Phocoena or “dolphin seal”, because they resembled both — so we’re not the first to be confused. The Dall’s porpoise is named after William Dall, a quartermaster on a whaling ship who collected the first specimen off Alaska in 1873.
It seems that these porpoise species can’t always tell each other apart either, for DNA analysis shows that they occasionally interbreed. The habit of the male Dall’s porpoise is to select one female and stay with her throughout a breeding season, while the harbour porpoise breeds promiscuously with several mates, even hitting on the occasional Dall’s female. The resulting hybrids often travel alone (although porpoises usually travel in large groups), or with a Dall’s mother. Cetacean personal relationships are complicated.
How is it that so many cetacean species flourish off the Pacific Northwest without territorial conflict? The key seems to be that they have co-evolved to consume different prey. Among local orcas, the northern, southern and migrant sub-groups aren’t competing for the same food. Migrant orcas for instance hunt marine mammals, the southern residents only salmon. As a result, orcas have not evolved the traits of fighters and aggressors. Although some orcas off California include humpback calves in their kills, Salish Sea orcas fight no other cetaceans, operate in families led by experienced matriarchs, and share fish with each other, the older giving food to younger relatives.
Prey specialization has its hazards, however. Southern resident orcas eat the large chinook (tyee) salmon almost exclusively, and what this does bring them into competition with, is us. Guess who’s winning? Human fishers don’t only take most of the chinook/tyee, but industry pollutes the waterways and degrades the rivers these salmon need to spawn in. Not only are local orcas starving, but the mighty tyee they rely on is also getting smaller, due in turn to herring over-fishing and habitat degradation.
The federal government has proposed a recovery plan for southern resident killer whales, as they were required to do by law when those orcas were designated endangered under the Species At Risk Act in 2003. Scientists have urged that this plan, after so long a delay, be robust and immediate, many calling for a moratorium on chinook fishing until stocks rebuild.
When the earliest human tribes radiated across the globe they fought each other for resources (and the warlike hero has been celebrated in literature ever since). By contrast, different eco-types of whales have for eons shared the same bays and deep ocean canyons without conflict. Cooperative living facilitates the selection of genes for complex social organization and communication, individual loyalty and tend-and-befriend behaviours. If Salish Sea orcas go extinct now, we will lose not only a sub-species but also an advanced culture of peace rare on this planet.
Barbara Julien is a local writer and nature enthusiast. She writes here monthly about the various species making their home in Oak Bay.