A new study has documented for the first time the unique cooperative hunting behavior between killer whales and dolphins, showing that killer whales will "follow closely" a pod of Pacific white-sided dolphins, using them as "scouts" with sonar capabilities to jointly search for large Chinook salmon in deep water.
The international team, led by Canada's Dalhousie University, conducted research off the coast of British Columbia, using aerial drones, underwater video, acoustic recordings and the first ever use of Customized Animal Tracking System (CATS) suction-cup movement tracking tags on a resident killer whale population to reconstruct this unprecedentedly complex hunting process.
Researchers have found that when killer whales encounter a pod of Pacific white-sided dolphins, they significantly reduce the intensity of their own echolocation sounds, allowing them to better hear and track the movements of the dolphins heading toward schools of salmon. Because these salmon are too large, it is difficult for the dolphins to directly prey on them. They "navigate" in front and "lead" the killer whales to the vicinity of the fish school. The killer whales will drive the fish schools to the surface of the water, where other members of the group will quickly round up and devour them. When killer whales bite and swallow large fish, a large number of small pieces of fish meat will remain, which becomes a "meal of fragments" that dolphins can easily forage for. The two parties thus form a mutually beneficial and symbiotic cooperative hunting model.
During the entire observation process, scientists did not see any aggression or driving behavior between killer whales and dolphins, which further supports the judgment of "cooperative foraging" rather than accidental food competition or one-way utilization. The research team also speculated that by relying on dolphins' action cues, killer whales may reduce their own energy consumption of long-term echolocation to a certain extent and target scattered schools of salmon in deep water with greater efficiency. Some scholars pointed out that killer whales can therefore be regarded as "outsourcing" part of the search task, and dolphins not only obtain prey fragments, but also reduce the risk of being hunted by "wandering" killer whales that prey on dolphins by partnering with resident killer whales that do not prey on dolphins.
The researchers believe the relationship may go beyond foraging benefits. For dolphins, long-term mixing with a specific group of killer whales that do not feed on dolphins helps them distinguish different types of killer whales through sound characteristics, thereby better identifying real natural enemies in the open ocean. From "safe shelter" to "acoustic learning" to "shared trophies", this series of potential benefits makes dolphins continue to choose to travel with these killer whales, and also lays the foundation for the two parties to maintain long-term cooperation.
Although this shooting and monitoring provide unprecedented first-hand evidence, scientists emphasize that this is only the starting point for understanding this coordinated system, and many key questions remain to be answered. For example, do killer whales that team up with dolphins have a significantly higher success rate in catching salmon than individuals hunting alone? Will this cooperation translate into better body condition or greater reproductive success in the long term? The research team said that the next step will be to assess the prevalence and ecological significance of this cross-species coordinated predation in local killer whale and dolphin populations through more long-term tracking and quantitative analysis.