Scientists Record First-Ever Cooperative Hunting of Killer Whales and Dolphins

Scientists have long known that resident killer whales interact with Pacific white-sided dolphins, but observing them dive and hunt in unison completely changes our understanding of what these encounters mean. "We've known for a long time that resident killer whales interact with Pacific white-sided dolphins, but seeing them dive and hunt together in unison completely changes our understanding of what these encounters mean," says lead author Sarah Fortune, a professor in the Department of Oceanography at Dalhousie University. It was known that killer whales and dolphins interact in the waters of the Pacific Ocean, but no cooperation between them had ever been observed. A strategic alliance For the authors, this alliance between killer whales and dolphins benefits the dolphins, which are protected by the whales and can feed on the remains of the hunt, while the killer whales are able to locate salmon more easily with the help of the dolphins. Although the authors acknowledge that more research is needed to confirm the hypothesis, the authors believe the alliance benefits dolphins by providing protection and access to hunting scraps, while killer whales use the dolphins' echolocation to find salmon. On one occasion, the dolphins fed on the remains of an adult Chinook salmon that had been torn apart by the killer whales so the dolphins could eat it, which the authors say is evidence that both species share prey. However, in the videos, the killer whales and dolphins do not fight for food or avoid each other; instead, they exhibit behavior suggesting both species have forged a cooperative relationship from which both benefit, the authors point out. The authors believe that killer whales muffle their own noises to hear the dolphins' echolocation and locate Chinook salmon (Oncorhynchus tshawytscha), which are prey too large for the dolphins to capture and swallow on their own. "Our material shows that killer whales and dolphins may actually be cooperating to find and share prey, something never before documented in this population," Fortune emphasizes. While it is common to see Pacific white-sided dolphins hunting along the coast of British Columbia just meters from killer whales, this type of whale hunts independently and only shares prey with members of its pod. The authors also recorded eight occasions where killer whales captured, ate, and shared Chinook salmon with other killer whales. "By working together, killer whales can conserve energy and use dolphins as radar-equipped scouts to increase their chances of finding large Chinook salmon at greater depths. On 25 occasions, killer whales changed course after encountering dolphins to follow them on feeding dives." "The strategic alliance we observe between dolphins and killer whales is extraordinary," highlights lead author Andrew Trites, director of the Marine Mammal Research Unit at the UBC Institute of Oceans and Fisheries. Unprecedented footage Fortune and her team studied the hunting behaviors of nine killer whales and their interactions with Pacific white-sided dolphins around Vancouver Island, Canada, in August 2020. The footage, collected by Canadian scientists, shows for the first time a group of killer whales (Orcinus orca) and Pacific white-sided dolphins (Lagenorhynchus obliquidens) hunting together in the waters off British Columbia (Canada) and sharing fish scraps after the kill. In return, the dolphins gain protection from predators and access to the scraps of one of the ocean's most prized fish. In four of these occasions, the dolphins were present. Now, for the first time, a scientific team has recorded a group of killer whales and dolphins hunting together and sharing the spoils. To do this, they used drones and attached biologging tags with suction cups to the backs of the killer whales (which then fall off), in this way, to collect aerial and underwater footage of the animals' coordinated interactions. "It's a mutual benefit for all involved," concludes Trites. The killer whale tracking tags allowed the researchers to collect 3D kinematic data with images and sound and continuously record high-resolution dive data, along with vocalizations and feeding-related sounds. The research, conducted by scientists from Dalhousie University, the University of British Columbia (UBC) and the Hakai Institute (Canada) in collaboration with the Leibniz Institute (Germany), has been published in Scientific Reports.