Orcas and dolphins caught on video collaborating to hunt salmon

When dolphins swam onto the scene during a study on northern resident orcas off the coast of B.C., at least one researcher admitted to being a little annoyed.

The Pacific white-sided dolphins had nothing to do with the study at hand.

The research group — a collaboration between Dalhousie University, the University of British Columbia (UBC), the Leibniz Institute and the Hakai Institute — wanted to understand how northern resident orcas find food, and compare that to the struggling southern resident population.

But those seemingly annoying dolphins ended up offering an unexpected glimpse into their symbiotic foraging relationship with the orcas, according to new research published in Scientific Reports.

The researchers found the dolphins were helping the orcas hunt Chinook salmon.

Dolphins have often been considered “pesky critters” who steal fish from the orcas, according to Sarah Fortune, assistant professor of oceanography at Dalhousie University in Halifax and Canadian Wildlife Federation chair of large whale conservation.

But that’s not what was happening — on deep, deep dives below, the dolphins and orcas were communicating.

“It became really clear that the dolphins weren't there for a free lunch,” said Fortune, the study’s lead author.

“They were actually exerting time and energy to dive deep, to chase the salmon.”

Andrew Trites, professor and director of the marine mammal research unit at the Institute for the Oceans and Fisheries at UBC and study co-author, said videos showed orcas following the dolphins down on dives.

“That seemed a little bit odd,” Trites said.

And recordings of the mammals’ echolocation seemed to indicate the orcas were eavesdropping on the dolphins too.

“We were noticing that the killer whale was going quiet, and it was listening to the pings from the Pacific white-sided dolphins.”

The dolphins were scouting out the salmon, Trites said.