A pod of Pacific white-sided dolphins off the coast of British Columbia have been observed cooperating with orcas, a traditional enemy that’s better known for taking out great white sharks than friendly interaction.Scientists say they have documented the dolphins and a local population of killer whales known as Northern Resident orcas teaming up to hunt the orcas’ staple food: salmon. Though other groups of orcas feast on dolphins, Northern Residents do not. Still, it is the first time this type of cooperative behavior has been documented between the two marine mammals, researchers reported.“Seeing them dive and hunt in sync with dolphins completely changes our understanding of what those encounters mean,” said Sarah Fortune, Canadian Wildlife Federation chair in large whale conservation and an assistant professor in Dalhousie University’s oceanography department. Fortune was the lead author of the study, which published Thursday in the journal Scientific Reports.AdvertisementAdvertisementAdvertisementAdvertisementTo witness the dolphins and orcas interacting, the researchers captured drone footage as well as underwater video by attaching suction tags to the orcas that were equipped with cameras and hydrophones.Their footage showed that the killer whales traveled toward the dolphins and followed them at the surface level. The underwater footage revealed that the killer whales were also following dolphins on their dives of up to 60 meters (197 feet), where the orcas were able to prey on Chinook salmon.Though light levels are low at those depths, Fortune said cameras picked up the killer whales catching salmon, with clouds of blood billowing from their mouths, and hydrophones picked up the crunch of a kill.To understand better what was happening, the researchers also eavesdropped on the echolocation clicks made by dolphins and orcas, which allow animals to navigate and sense their environment by listening to the returned echoes of the noises they make. “We can look at the characteristics of these clicks to infer whether a whale is actively chasing a prey for a fish and also whether it may have caught the fish,” Fortune said.AdvertisementAdvertisementAdvertisementAdvertisementThe researchers recorded 258 instances of dolphins and orcas interacting between August 15 and 30, 2020.They found that all the whales that interacted with dolphins also engaged in killing, eating and searching for sa …
