Northern resident killer whales are ferocious hunters with an appetite for adult salmon. Pacific white-sided dolphins prefer considerably smaller prey. And yet, in at least some cases, the two hunt together.
That’s the exciting discovery detailed in a recent paper, “Cooperative foraging between dolphins and fish-eating killer whales,” published on Dec. 11, 2025, in Scientific Reports.
Researchers employed high-tech equipment, including video recorders and sensors, to capture the marine mammals in action. These methods revealed an incredible pattern: dolphins acting as “scouts” to help killer whales find salmon.
Orcas and Dolphins Join Forces: A Tale of Two Species
A particular population of orcas, known as northern resident killer whales, has often been seen swimming within metres of Pacific white-sided dolphins in the waters off British Columbia. Before the recent study, experts could only speculate as to why the orcas and dolphins appeared together.
One theory held that the dolphins were stealing prey from the larger orcas, which would represent a “kleptoparasitic” relationship. It also seemed possible that the dolphins could be using the orcas for protection from potential predators, including sharks and other populations of mammal-eating orcas.
A third hypothesis was that the dolphins approached the orcas to learn more about their acoustic signals — a useful bit of knowledge, since it would allow the dolphins to distinguish the fish-eating orcas from their mammal-eating cousins.
Ultimately, it was a fourth hypothesis that proved most well-founded: Orcas and dolphins were hunting together in a process called “cooperative foraging.”
A Tech-Heavy Investigation
The study into the orca-dolphin relationship was led by researchers Sarah M. E. Fortune, Xi Cheng, Keith Holmes, and Andrew W. Trites. The team journeyed into the marine mammals’ habitat on a boat measuring 16 metres. From there, they observed the animals’ behavior with a Bond-like assortment of gizmos and gadgets.
With fibre poles, the researchers attached suction cup sensors to the orcas’ sides. These sensors could measure the orcas’ dive patterns, capture sounds, and even record video. The sensors eventually weakened their hold and detached themselves from the orcas. Meanwhile, the team used drones to watch the marine mammals from above.
Once data had been harvested, the researchers conducted a quantitative analysis of the animals’ interactions. It was this analysis that revealed the extent of interspecies collaboration.
Exciting Observations
During just four days of observation, the research team captured 258 instances of dolphins and orcas moving together. These interactions always occurred while the killer whales were hunting.
Interestingly, the dolphins didn’t appear to be following the orcas. Rather, it was the orcas that were following the dolphins. “[T]he dolphins appeared to be in a leadership role,” says Sarah Fortune, the paper’s lead author.
It was this observation that led the researchers to conclude that the dolphins were acting as “scouts.” They would lead the orcas to a school of chinook salmon, let the orcas slaughter their prey, and then feast on the scattered remains.
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More Research Ahead
It would appear that the orcas and the Pacific white-sided dolphins have adapted the practice of collaborative hunting because it benefits both of them. The orcas are led directly to their favorite prey, while the dolphins can gorge themselves on the orcas’ scraps.
That said, the extent of the benefits for each species remains unknown. The authors of the study think this is a pressing point for further exploration.
“Do killer whales that forage with dolphins have better success catching salmon?” Dr. Fortune wonders. “Is their body condition better than those that hunt alone? These are the kinds of metrics we can use to figure out whether this is a mutually beneficial interaction.”
Once further research is conducted, we’ll know even more about this fascinating interspecies relationship.
Editor’s Note: The opinions expressed here by the authors are their own, not those of impakter.com — In The Cover Photo: Orcas at sea. Cover Photo Credit: Ivan Stecko.
