Orcas and dolphins caught on video cooperating 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.
Pacific white-sided dolphins had no involvement with the current study.
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 it to the struggling southern resident population.
But according to newly published research, the seemingly troublesome dolphins offered an unexpected glimpse of their symbiotic relationship with orcas. scientific report,
Researchers found that the dolphins were helping the orcas hunt Chinook salmon.
According to Sarah Fortune, an assistant professor of oceanography at Dalhousie University in Halifax and chair of the Canadian Wildlife Federation for Large Whale Conservation, dolphins are often considered “strange creatures” that steal fish from orcas.
But that wasn’t happening – deep, deep down, the dolphins and orcas were communicating.
“It became really clear that the dolphins were not in for a free lunch,” said Fortune, the study’s lead author.
“They were really putting time and energy into diving deep to chase the salmon.”
How the orca-dolphin partnership works
Andrew Trites, professor and director of the Marine Mammal Research Unit in the Institute of Oceans and Fisheries at UBC and co-author of the study, said the video shows the orcas chasing the diving dolphins.
“It seemed a little strange,” Trites said.
And recordings of the mammals’ echolocation appear to suggest that orcas were also eavesdropping on dolphins.
“We were watching the killer whales go by, and they were listening to the calls of Pacific white-sided dolphins.”
The dolphins were searching for salmon, Trites said.
“They were kind of spread out and pinging through the water over a much wider area than the whales could search – and the whales were listening.”
The orcas could recognize when the dolphins found a large Chinook salmon. Then they went in for the kill.
“We can hear the crunching sound as it bites the fish hard – literally, it’s a real crunch,” Trites said.
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The orcas shared their prey with other orcas, and in the ensuing bloody, messy feast, the dolphins ate bits of meat and tissue.
“This is their payment,” Trites said, adding that the salmon is so large that the dolphins can’t eat it without the orcas’ help.
“At the end of a successful fishing trip everyone is happy, everyone gets food.”
Trites said dolphins are not thieves who steal fish from orcas.
“Killer whales are very big. They can take out dolphins if they want to. They’re very, very tolerant of them. And so there’s absolutely no aggression in them.”
How was the research done?
The two-year study conducted its fieldwork in Queen Charlotte Strait, Johnstone Strait and Queen Charlotte Sound in the summer of 2019 and 2020, Fortune said.
Researchers collected underwater footage with tags attached to the orcas, Fortune said.
The tags will remain on for several hours and eventually turn off, floating to the surface and sending signals to satellites overhead.
Researchers retrieved the tags, downloaded the data and watched the “orca-eye view,” called “Orca TV” by Trites.
Drone videography shares the more traditional “bird’s eye view”.
Drone pilot, geographer and fellow researcher Keith Holmes of the Hakai Institute was the first to observe the dolphin-orca interaction.
“At first you’re like, ‘Oh, get out of here. We’re trying to do some research,'” he said sarcastically, admitting to being “a little annoyed.”
“But then you see them diving together, and you know, it’s really unique in the animal world,” he said.
Study shows ‘cooperation and connection’ of animals
The hours-long dive took place over several days – the footage showed “all these interesting underwater acrobatics”, Holmes said.
Holmes said while the new videos raise many more questions, they also document another piece of the puzzle that isn’t often seen.
“This is further evidence of what kind of complexities are going on there.”
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Researchers recorded 258 “unique” incidents of dolphins traveling near tagged orcas.
Researchers only observed dolphin interactions in 2020.
BC Whales CEO and lead researcher Jenny Ray, who was not involved in the research, said the study is fascinating.
“This is a research paper that really needs to come out,” she said. “It really shows the cooperation and connection of animals with each other in nature.”
He said it was not surprising that two species would help each other with different foraging techniques.
“This is something we’ve actually seen a lot with other species,” she said, offering the example of sea lions “hanging out” with humpback whales to snack on small pieces of food left over from the whales.
Fortune said next steps will include investigating whether some matrilines of northern residents prefer to feed with dolphins — and if they do, whether those matrilines are in better physical condition.
Fortune said, “Maybe (dolphins) are more useful than we gave them credit for. So yes, don’t ignore the dolphins.”
