Orcas are the ocean's top predators. Even great white sharks, the world's largest predatory fish, are no match for orcas that hunt in groups. The same goes for large baleen whales and highly intelligent dolphins. For the first time, the "killer whale," notorious for its ferocity, has been captured hunting together with dolphins and sharing prey. It seems nature has produced the logic that anyone will join hands if it is to their advantage.
A team led by Sarah Fortune of Dalhousie University's department of oceanography said it "first observed orcas (Orcinus orca) hunting together with Pacific white-sided dolphins (Lagenorhynchus obliquidens) off the coast of British Columbia in eastern Canada," according to a paper published on the 12th in the journal Scientific Reports. The orcas and dolphins later shared their prey.
◇Hunting behavior filmed underwater and from the air
Off the coast of British Columbia, Pacific white-sided dolphins are often seen hunting just a few meters from orcas, their natural predators. Because the two species showed no signs of fighting or avoiding each other, the researchers hypothesized that the behavior could be due to cooperation rather than competition for food.
In Aug. 2020, Fortune's team investigated how nine orcas hunted around Vancouver Island, British Columbia. The researchers attached cameras and sensors with suction cups to the orcas to collect underwater video, audio, and movement data. They also filmed from the air with drones at the same time.
The team recorded 258 instances of dolphin behavior while moving with the orcas fitted with suction cups. During this process, they found 25 cases in which orcas changed course and dove after the dolphins. The two species showed no behavior suggesting attack or avoidance. The researchers said the orcas and dolphins divided roles and both benefited while hunting Chinook salmon (Oncorhynchus tshawytscha).
Dolphins excel at echolocation. Orcas dove to reduce noise so they could listen for the dolphins' sonar signals. It is not a bad thing for the dolphins to have orcas following, either. Chinook salmon are large, making them hard for dolphins to swallow in one bite. The researchers observed eight cases in which orcas caught salmon and shared them with companions. Remarkably, in half of those cases, dolphins were included. When orcas cut large salmon into pieces, dolphins can eat them more easily. The team described this as prey sharing between the two species.
◇May deter attacks from other orca pods
Andrew Trites, a co-author of the paper and professor in the department of zoology at the University of British Columbia, said, "The strategic alliance observed between dolphins and orcas is a remarkable phenomenon," adding that "it is a win-win relationship where everyone benefits." He said orcas could use dolphins like scouts equipped with radar to increase the chances of finding Chinook salmon at depth. In return, dolphins receive salmon in a form that is easy to eat, so both benefit.
Fortune said, "We have long known that orcas inhabiting the coast of British Columbia interact with Pacific white-sided dolphins, but actually observing them diving and hunting together gave us a completely new understanding of the meaning of their encounters," adding, "The video we captured shows that orcas and dolphins can in fact cooperate to find and share food."
The cooperation between the two species can be seen as predators adapting to a changing marine environment. The orcas that hunt salmon by following dolphins are a resident pod living off the coast of British Columbia. The researchers said, "Dolphins may also gain protection from other transient orca pods passing through the area by hunting with the resident orcas," adding, "Further research is needed to understand how widespread and consistent this cooperative behavior is."
The study was conducted jointly by researchers from Dalhousie University, the University of British Columbia, the Hakai Institute, and the Leibniz Institute for Zoo and Wildlife Research in Germany.
References
Scientific Reports (2025), DOI: https://doi.org/10.1038/s41598-025-22718-4