Mayne Island Conservancy is excited to be part of a new conservation initiative, in partnership with our neighbouring island conservancies, that focuses on the future of the Strait of Georgia’s whales, dolphins, and porpoises (collectively called cetaceans), and the health of their habitats.
In The Beginning
You might remember learning in biology class that life began in the ocean. With the marine mammals, it’s interesting to note that these aren’t animals that stayed behind—rather, these were land-going mammals that made their way to the ocean to take advantage of its abundant food.
Is a dolphin a whale? Is a killer whale a dolphin?
Yes, and yes. First of all, we can think of the cetaceans in two major groups: the baleen whales and the toothed whales. These are two different families that split apart about 30 million years ago. In our waters, the baleen whales are represented most often by the humpback and the gray whale. Both of these make a living by eating industrial quantities of very small things, which they strain through the baleen (a giant ‘comb’ of stiff, bristly fibre) in their huge toothless mouths. The minke whale (pronounced minky) also belong to this group. It’s a little harder to spot because of its small size and shy habit, but it’s not rare in our waters.
Toothed whales, as their name suggests, have an impressive array of teeth in their mouths. In BC they range in size from the tiny harbour porpoise to the giant sperm whales (think Moby Dick) that are found in the open Pacific. Toothed whales are echo-locators, and most of them are able to function effortlessly in total darkness thanks to their system of producing high clicks through an organ within their blowhole and receiving the echoes back, first through their jawbones and then through the ear canal. They can find fish, spot obstacles, and communicate with each other perfectly well—except when ship noise and military sonar get in their way.
Dolphins and Porpoises
These are two different families of small toothed cetaceans. Dolphins and porpoises split apart about 15 million years ago. They’re pretty similar on the outside, but porpoises have spade-shaped teeth while dolphins have dozens of conical teeth. In our waters we have the harbour porpoise, just over a metre in length and surprisingly common when you look for them. The best time to see them is when the sea is completely calm—it’s not at all unusual to spot a few from the ferry between Mayne and Swartz Bay. They almost never hang out in large groups, and never breach out of the water; all you see is a quick and subtle dorsal fin arching just barely out of the water and disappearing again.
Less commonly seen in the southern Strait of Georgia is the Dall’s porpoise, an inquisitive and energetic porpoise that is coloured a bit like a miniature killer whale. They often approach vessels that are cruising at a speed of nine knots or so, and seem to enjoy travelling in a boat’s wake or bow wave. Dall’s porpoises almost never jump out of the water; rather, they speed along just under the surface and make a rooster tail of spray as they break the surface to breathe.
We have two types of dolphins that we can expect to see around here: killer whales and Pacific white-sided dolphins. Interestingly (and alarmingly) we can expect to see more dolphin diversity with global warming; some of the warm-water dolphins like bottlenose and common dolphins are showing up off our coast more frequently.
Pacific white-sided dolphins are fast, inquisitive, acrobatic, and social. They travel in groups of a few animals to ‘herds’ of thousands. These dolphins can be spotted from afar as they arc high out of the water, occasionally flipping and breaching on their side. They often go out of their way to investigate vessels and dart along with them for a while.
Our most famous dolphin, as well as our most endangered, is the orca or killer whale. Orca is its Latin name; many people prefer that name to “killer whale” though in BC the conservation and science communities tend to use the latter term. It’s an accurate moniker; these are the ocean’s top predators. In our waters, there are two distinct groups, now considered distinct species. We have the Biggs’ or transient killer whale, which eat marine mammals for a living, and we have resident killer whales that are exclusively fish-eaters— in our waters they are dependent on salmon—mostly chinook with some chum—for their survival.
While Biggs’ killer whales are doing reasonably well, the southern resident killer whale is in trouble. Its future is linked to the wellbeing of our salmon population, and the future of salmon depends on us.
We’ll look at ways to help our amazing marine mammals in future articles.