Transient orca sightings in Salish Sea setting all-time record

Mark Malleson watched an orca toss a harbour porpoise in the air, leap up and grab it in its mouth, then spit it out, on Wednesday.

Apparently transient orcas — all known as Bigg’s orcas and “the Ts” — like to play with their food.

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“Harbour porpoise chases are pretty exciting,” said Malleson, a skipper with the Prince of Whales tour company, who also works for the Department of Fisheries and Oceans and volunteers with the Center for Whale Research on San Juan Island.

Anecdotes like that one are abundant this season. According to the Pacific Whale Watch Association, this summer marks the highest number of transient orca sightings in the Salish Sea on record. The PWWA gathers data from 33 tour operators.

In the 76 calendar days between June 1 and Aug. 15, operators have reported seeing transient whales on at least 49 days. Although PWWA had not aggregated last year’s numbers, Harris said it’s a noticeable increase.

That means researchers are learning more about the way transient orcas eat, hunt and interact with each other.

“It’s an emerging science,” PWWA executive director Michael Harris said.

“We know so little about them. So the fact that they’re coming into an area like this that is so well-studied and well-known and that is populated with lots of researchers and scientists — it’s a great opportunity for all of us to get out there and observe what they do and how they do it.”

The most notable difference between transient and resident orcas, which usually call the waters around Victoria home, is diet: Transient orcas eat marine mammals, while resident orcas favour fish.

But there are other differences, too: Transient whales don’t live in pods, or tightly knit families, instead travelling in small groups of two to six. They tend to change location every few years. And they have a “sleeker” look with more pointed dorsal fins.

Harris credits an influx of marine mammals — including harbour seals — for the transients’ presence. He said transients pose no threat to the ecosystem, instead acting as a force to even out imbalances.

“They’re the equalizers. Right now, we have a boom of harbour seals out there and they are correcting the balance, bringing the numbers down,” he said.

“When it gets to the point where we have a good carrying capacity for harbour seals, [the transients] might move to another area.”

Observers are seeing transients do things they might not have seen before — in one case, it was attacking a bird. In another, it was creating bubbles to distract prey. And in a few cases, it has meant getting closer to resident pods than usual.

“I’ve witnessed a few occasions where they’ve bumped into each other like a couple of gangs in an alley,” said Malleson.

The residents usually scare off the transients pretty quickly. “And the transients usually give them a wide berth,” he said.

The B.C. Cetacean Sightings Network doesn’t tally its counts until the end of the year, but co-ordinator Tessa Danelesko said it’s safe to say transient populations are increasing.

“We’re seeing the population grow by about two to three per cent a year. And we do think that’s directly linked to prey availability,” said Danelesko, who is also a researcher at the Vancouver Aquarium.

Historically, there was a bounty on seals in the Strait of Georgia, so they were hunted for their pelts until about the early 1970s, she said. Seal populations began to stabilize in the mid-1990s.

“It seems like the Biggs’ population is catching up now,” she said.

The network believes there are about 300 transient whales living between Alaska and California, based on reports.

It doesn’t mean they’re here to stay, however. Transient orcas tend to take up residence in an area for a few years, then move to a new region, Harris said.

asmart@timescolonist.com

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