Killer Whales Team Up With Dolphins to Hunt Salmon in Noisy Waters

Sometimes they even leave the dolphins scraps.

Off the coast of British Columbia, researchers have reported something that looks a lot like teamwork between two predators that don’t usually get credit for cooperating: Orcas (a.k.a. killer whales) and Pacific white-sided dolphins.

In observations around Vancouver Island in August 2020, a small group of northern resident orcas repeatedly did an about-face after meeting the dolphins. However, the orca pods weren’t hunting them; they were using them to help find food. The orcas followed the dolphins as they dove to forage.

Scientists behind the new study, published in Scientific Reports, say this is the first documented evidence suggesting cooperative hunting between orcas and dolphins — at least in this setting — centered on a prized target: Chinook salmon, generally too large for these dolphins to handle on their own.

An unlikely partnership

The report describes a pattern that feels almost strategic. Dolphins are fast, agile and equipped with echolocation — they produce clicks and listen for echoes to detect prey underwater. Orcas, on the other hand, are powerful hunters that can take down the big salmon, but finding those fish in a vast, noisy ocean is not always simple.

The researchers tracked nine northern resident orcas and documented their interactions with dolphins using multiple tools such as movement data, underwater video, acoustic recordings and aerial drone footage. The mix of tracking methods lets the team compare where the animals moved, what they were doing below the surface, and what was happening in the soundscape without relying on a single viewpoint.

Twenty-five instances were recorded of orcas altering their path after encountering dolphins, then following them on foraging dives. The idea is not that dolphins are “leading” the whales on purpose like tour guides. Instead, the authors suggest something more subtle: The orcas might be quieting their own noise so they can listen for dolphin echolocation, using the dolphins’ clicking as a kind of biological search signal that hints where salmon are moving.

If that sounds far-fetched, consider how much the ocean is about information. Underwater visibility can be limited and prey can be patchy. When another predator is actively scanning and chasing, that activity can be useful.

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The study also includes moments that hint at a possible payoff for the dolphins.

The researchers observed eight cases where orcas caught Chinook salmon, ate, and shared the fish with other orcas. Dolphins were present for four of those events. In one case, the dolphins were seen scavenging the remains of an adult Chinook after the whales had actually broken it into scraps small enough for dolphins to swallow. The authors interpret this as prey sharing — or, at the very least, an opportunity created by the whales that the dolphins can exploit.

That detail matters because it helps answer the question of what do dolphins get out of chasing salmon they can’t really eat? If the dolphins sometimes end up with edible leftovers, tagging along could be worth the energy.

The paper also raises a second possible benefit: Safety. Orcas come in different ecotypes and social groups, and not all are equally friendly to smaller marine mammals. The authors suggest that being near local orca groups could reduce risk from other orca pods passing through. However, the authors state that the hypothesis needs to be tested with more observations.

Still, this kind of relationship — two smart, social species moving together, hunting in the same area and occasionally sharing a meal’s aftermath — pushes against the simpler story that predators always compete.

It also arrives at a time when Chinook salmon are a high-stakes food source in the Pacific Northwest. Northern resident killer whales are known for specializing in fish, and Chinook are often described as a preferred prey item because they’re large and energy-rich. Any behavior that improves the odds of locating salmon, especially in periods when salmon are harder to find, could make a difference for how these orcas spend their time and energy.

The study adds a new example of how flexible marine predators can be. Orcas are already known for complex social lives and specialized hunting styles. Dolphins are famously curious and highly communicative. Put them in the same water with a shared interest and it may not be surprising that the relationship starts to blur.