Researchers have observed killer whales and Pacific white-sided dolphins working together to catch Chinook salmon off northern Vancouver Island. The orcas dive deep with the dolphins to locate the fish, then eat most of it while the dolphins scavenge the remains. This interspecies collaboration highlights the complex social behaviors of marine mammals.
Off the coast of northern Vancouver Island in the northern Pacific Ocean, killer whales, also known as orcas, have been documented foraging cooperatively with Pacific white-sided dolphins to hunt Chinook salmon. Scientists equipped nine orcas with video cameras and sensors, capturing footage of four whales diving alongside numerous dolphins toward salmon hiding at depths of up to 60 meters. Drones observed three additional whales in similar interactions. In total, six out of 12 whales faced the dolphins 102 times during these encounters.
The orcas consume the large Chinook salmon, which can exceed one meter in length and are typically too big for dolphins to catch alone. However, the whales' messy feeding habits—tearing the fish apart to share with family—leave blood, scales, and fragments that the dolphins eagerly scavenge. Researchers suggest the dolphins assist by scouting the salmon, using their clicks and buzzes to scan the dark, rocky depths where fish seek cover.
"They were cooperatively foraging," says Sarah Fortune at Dalhousie University in Canada. "You could anthropomorphise it and say that they’re being friends for hunting purposes." Sensor data showed the orcas reducing their own echolocation, likely to eavesdrop on the dolphins' broader scanning sounds. "It’s like turning on the high beams on a car," Fortune explains, "and the light is the sound."
This behavior contrasts with typical orca interactions with other species, which often involve predation or harassment, such as recent boat-ramming incidents off the Iberian Peninsula. Examples of interspecies cooperation elsewhere include fish guiding octopuses to crustaceans or honeyguide birds leading humans to beehives.
Not all experts agree on the cooperative nature. Brittany Visona-Kelly at Ocean Wise, a conservation organization, contends that dolphins are primarily stealing scraps rather than actively partnering. Her recent study using drone footage in the same region depicted orcas ignoring, playing with, or even lunging at dolphins, suggesting the dolphins seek protection from Biggs' killer whales, a mammal-eating population that avoids resident orcas. "We observed no clear evidence of benefits to the killer whales," Visona-Kelly states.
A separate incident last month involved 30 to 40 dolphins circling an emaciated orca named I76, potentially exhausting it before it resurfaced. Despite such tensions, Luke Rendell at the University of St Andrews in the UK views the new findings as convincing evidence of cooperation. "These animals are smart and behaviourally flexible," he says. "We’ll see all kinds of interactions between killer whales and dolphins, everything from the killer whales eating them to playing with them to cooperating with them."
The research appears in Nature Scientific Reports (DOI: 10.1038/s41598-025-22718-4).
