Scientists have captured footage that appears to show orcas and Pacific white-sided dolphins teaming up to hunt salmon off the coast of British Columbia – the first time this behaviour has ever been recorded.
The findings, published last Thursday in Scientific Reports, reveal that these encounters between northern resident orcas and dolphins aren't just chance meetings while searching for food.
Researchers from the University of British Columbia, the Leibniz Institute and the Hakai Institute worked together on the study.
"These whales are top salmon hunting specialists. They're highly specialised and highly skilled predators," said Sarah Fortune, a marine scientist at Dalhousie University and the study's lead author.
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"To see them following dolphins as though they were leaders was really counterintuitive and really exciting."
To capture this behaviour, the team used various pieces of technology, such as drones filming from above, cameras attached to the whales with suction cups, and hydrophones recording underwater sounds.
Over 15 days, researchers documented 258 separate interactions between the two species around Vancouver Island.
The underwater footage proved particularly striking, showing orcas following dolphins down to depths of 60 metres where they hunted Chinook salmon together.
Scientists have captured footage showing orcas and Pacific white-sided dolphins teaming up to hunt salmon off the coast of British Columbia – the first time this cooperative behaviour has ever been recorded
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"Seeing them dive and hunt in sync with dolphins completely changes our understanding of what those encounters mean," Ms Fortune explained.
The cameras picked up killer whales catching their prey, with clouds of blood visible in the water, while hydrophones recorded the distinctive crunch of a successful kill.
It turns out the dolphins appear to be acting as scouts, using their quieter hunting style to locate Chinook salmon – fish that can grow to nearly three feet long and are too large for dolphins to catch themselves.
The orcas then follow closely behind, and when they catch and tear apart their prey to share with other pod members, the dolphins swoop in to grab the scraps.
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Dolphins and killer whales have never been spotted hunting before, although some argue that the footage does not show that this has changed
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While northern resident orcas don't hunt dolphins, Bigg's orcas – a different type sharing the same waters – do.
By sticking close to their salmon-hunting allies, dolphins gain protection from these predatory relatives, representing another huge benefit to this new arrangement.
Not everyone is convinced this represents genuine teamwork, though. Brittany Visona-Kelly, a senior manager at Ocean Wise's Whales Initiative who has studied these same orca populations for years, remains sceptical.
To capture the behaviour, the team used various pieces of technology, such as drones filming from above, cameras attached to the whales with suction cups, and hydrophones recording underwater sounds
| YOUTUBE"Over several years of observations, we concluded that dolphins and porpoises not killer whales benefit most from these encounters," she said, suggesting the orcas might simply tolerate the dolphins because chasing them away would waste too much energy.
Ms Fortune pushed back on this view, noting her team found no evidence of hostile behaviour from the orcas towards their dolphin companions.
Judith Bronstein, who studies interspecies cooperation at the University of Arizona, pointed out that while such partnerships are relatively common in nature, they're rarer among mammals and typically don't involve predators.
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