Study sheds new light on West Coast’s mammal-eating killer whales

New research is revealing fascinating differences within the transient killer whale population off Vancouver Island.

A study out of the University of British Columbia is shedding new light on the west coast transient killer whale population, finding two distinct communities that rarely mix.

For lead author Josh McInnes, the findings were two decades in the making.

“I travelled the whole coast looking for whales from basically southern B.C. to California,” he said.

McInnes is the founder of Oceanic Research Alliance and says he has discovered that there are distinct subpopulations, inner and outer coastal transients—two communities, two different habitats, two distinct diets.

The inner coastal population are seen as city dwellers, navigating inlets, bays and sheltered waterways. Their main food source is harbor seals and porpoise.

The outer coastal transients are seen as rural dwellers spending their time a few hundred kilometers offshore.

“They use the continental shelf break which is where the open ocean meets our continent,” said McInnes.

Those outer coastal killer whales hunt in deep canyons feeding off of dolphins, elephant seals and even juvenile grey whales.

Due to the two groups distinct diets the populations rarely mix.

“That becomes a behavioural thing, they learn how to hunt specific species which means they are going to associate with individuals that hunt the same,” said McInnes. “Therefore, you get this kind of social isolation between the two groups.”

McInnes says there are times when the two groups have been observed together although it’s only where their two habitats converge.

An example of that is where the continental shelf runs close to the California coast.

Dr. Anna Hall is a marine zoologist with Sea View Marine Sciences. She says she is not surprised by the study’s findings, given the complexity of the endangered species.

“We know that they know how to make the best use of their environment by not competing with each other,” said Hall.

“The more information that we have to understand habitat use that is farther away and in the offshore regions in the future, may help us better conserve creatures and do a better job of looking after our oceans.

Meanwhile McInnes believes these two subpopulations may not be alone.

“We do believe that there is a third one out there that we call Oceanic, they might be transients but we’re not entirely sure yet,” said McInnes.

That population is harder to observe, as they are thought to reside hundreds of kilometers off the coast.