Orcas and Dolphins Documented Cooperating in Chinook Salmon Hunts Off British Columbia

A novel cooperative dynamic between northern resident killer whales (Orcinus orca) and Pacific white-sided dolphins has been documented in the marine environment off British Columbia, near Vancouver Island. New scientific investigation provides evidence that this interspecies alliance during foraging dives represents a deliberate strategy, altering previous assumptions about their interactions in the Pacific Ocean.

The research, published in the journal Scientific Reports, involved a multi-institutional team including experts from the University of British Columbia (UBC), Dalhousie University, the Leibniz Institute, and the Hakai Institute. Evidence suggests the northern resident orcas actively track the movements of the dolphins, effectively positioning the smaller cetaceans as aquatic scouts locating prey. Researchers quantified this behavior by recording 25 distinct instances where the orcas adjusted their trajectory to follow dolphins during foraging descents. This coordinated activity was captured using suction-cup biologging tags affixed to the orcas, combined with high-resolution aerial drone footage provided by the Hakai Institute.

A clear division of labor and mutual benefit characterizes this observed collaboration. When the orcas successfully captured Chinook salmon, the dolphins were observed scavenging the resulting scraps, a behavior the orcas appeared to tolerate. Dr. Andrew Trites, a professor at UBC’s Institute for the Oceans and Fisheries, noted that this alliance allows the orcas to conserve energy by utilizing the dolphins as "radar-equipped scouts" for locating salmon at deeper levels. Acoustic data further supports the hypothesis that both species may be monitoring each other's echolocation clicks to pinpoint salmon locations.

The benefits for the Pacific white-sided dolphins extend beyond securing easy meals. Scientists suggest that associating closely with the resident orcas offers the dolphins a significant advantage in predator protection. Transient, mammal-eating killer whales frequent the same waters and prey on dolphins; the presence of the resident, fish-eating pod may deter these threats. Lead author Dr. Sarah Fortune from Dalhousie University stated that observing resident orcas follow dolphins was counterintuitive yet significant, marking the first documented recording of cooperative hunting and prey-sharing between these two species in this population.

Researchers recorded 258 unique events where dolphins traveled near the heads of the tagged orcas while the whales were engaged in foraging behaviors. While the study provides strong observational evidence for mutual advantage—energy conservation and scouting for the whales, and food/protection for the dolphins—further quantification is necessary to fully assess the extent of the benefits derived by each species. The findings underscore the ecological significance of such interspecies associations in shaping the complex marine food webs off the British Columbia coast.