Orcas and dolphins hunt together off Canada - cooperation, or coincidence?

A new study has captured something rarely documented in the wild: two cetacean predators appearing to “team up” to find and feed on salmon. Researchers working off British Columbia report that northern resident killer whales repeatedly changed course to follow Pacific white-sided dolphins during Chinook salmon foraging with drones, underwater footage and suction‑cup tags revealing coordinated movement both at the surface and at depth.

The observations were made during fieldwork around Vancouver Island in August 2020, but the findings have only just been published in Scientific Reports.

What the researchers saw

Across the dataset, dolphins were frequently close to tagged, actively-foraging orcas and on multiple occasions, the whales reoriented toward dolphins and followed them, after which both species dove, suggesting the encounter triggered a shared hunting sequence rather than a casual passing association.

Footage also suggests a plausible “division of labour”: dolphins can act like fast-moving, sonar-equipped searchers, while orcas specialist Chinook hunters can secure the prey and break it apart. Dolphins were seen scavenging scraps after orca kills, and the study notes how striking it was that the whales showed little to no obvious aggression during these close encounters.

So…cooperation, or something else?

It’s tempting to call this straightforward cooperation but in behavioural ecology, “cooperation” has a high bar. The key test is whether both species reliably gain a net benefit from the interaction, and whether the behaviour is repeatable and non-random.

This study makes a strong case that it’s not just chance proximity, because the associations were closely tied to foraging behaviour, with repeated course-changes and synchronised dives. But it also can’t yet prove a “win-win” in the strict sense, the authors note that the benefits to each species haven’t been quantified (for example, whether orcas catch more salmon, or expend less energy, when dolphins are present).

The researchers explicitly weigh alternative explanations too: dolphins could be opportunists (hanging around for scraps), could be seeking protection from mammal-eating Bigg’s orcas, or the relationship could be more complex than a tidy alliance. Some outside experts have also urged caution, suggesting the whales’ altered diving and reduced vocal activity could even be interpreted as avoidance rather than teamwork.

One of the most intriguing clues is acoustic: reporting on the study describes an alternating pattern of echolocation clicks picked up by the tags raising the possibility of “eavesdropping” as both species listen for each other’s sonar to widen the search for fish.

A wider pattern: cetaceans do form mixed-species “foraging teams”

This isn’t the only place cetaceans appear to gain an edge by associating across species. For example, false killer whales and bottlenose dolphins have been reported cooperatively feeding in New Zealand’s Hauraki Gulf. And a review of cetacean mixed-species groups notes that some associations may boost foraging success though benefits are not always mutual, and sometimes one species gains more than the other.

So whether this is true cooperation or a smart, low-conflict opportunism, the story underlines how adaptable and socially complex cetaceans can be.