Killer whales (orcas) and Pacific white-sided dolphins have been documented collaborating on salmon hunts off the coast of British Columbia, Canada, a behavior previously unrecorded in scientific literature. Researchers at Dalhousie University used a combination of underwater video, biologging tags, and drone footage to observe this unusual partnership in August 2020. The study, published in Scientific Reports, suggests a potential benefit for both species – though the exact nature of the cooperation remains under debate.
An Unlikely Partnership
Traditionally, orcas and dolphins maintain a neutral or sometimes aggressive relationship. Orcas are known to hunt dolphins in some regions, while dolphins occasionally mob orcas. However, in British Columbia’s northern resident orca population, this dynamic shifts. Researchers observed 258 instances of dolphins traveling near tagged orcas during foraging activity. In many cases, the orcas adjusted their course after encountering dolphins, diving together in what appears to be coordinated hunting behavior.
The researchers found that orcas sometimes break apart large Chinook salmon after catching them, and dolphins scavenge the remains. This suggests at least one way the dolphins benefit from the interaction: they can feed on fish too large for them to catch independently.
Why This Matters
This is the first documented evidence of cooperative hunting and prey-sharing between these two species. It raises questions about how marine mammals adapt to maximize food intake, and whether this behavior is widespread or unique to this specific region. The fact that orcas, highly intelligent predators, appear to be factoring in the presence of dolphins in their hunting strategy is particularly notable.
Debate Over Cooperation
Not all researchers agree this is true cooperation. Some suggest the dolphins are merely kleptoparasites, stealing scraps from orca kills. Others point out that the orcas may be avoiding dolphins rather than actively hunting with them, reducing vocal activity and taking longer dives when dolphins are nearby. The lead researcher, Sarah Fortune, acknowledges these alternative explanations.
“The dolphins might be the ones sneaking in and stealing the fish from the killer whales… but we have observations of dolphins going after salmon at the surface, so it’s clear that the dolphins want the salmon but they’re not necessarily well adapted to capture those big fish.”
Implications for Future Research
Understanding whether this behavior is truly cooperative, exploitative, or accidental is crucial. Further investigation is needed to quantify the benefits for both species and determine if this interaction is consistent across time and location. The study highlights how adaptable marine mammals can be, even forging unexpected alliances to improve hunting success.
Recent sightings of orcas engaging in unusual behaviors – wearing salmon on their heads, giving massages with kelp, and even damaging boats – reinforce the growing recognition of their complex social and cultural learning abilities. The orca-dolphin partnership is just one more example of the surprising intelligence and adaptability of these apex predators.
