Cooperation Between Dolphins and Orcas
A group of Pacific white-sided dolphins off the coast of British Columbia has been seen working alongside orcas, traditionally known for hunting instead of forming alliances. This behavior is particularly interesting given that orcas are often linked to taking on great white sharks.
Researchers have documented this partnership where the dolphins and a local group of Northern Resident orcas collaborate to hunt salmon, the orcas’ primary food source. While other orca populations are known to prey on dolphins, the Northern Residents typically do not. This cooperative hunting between the two species is reportedly a first.
“Observing their synchronized diving and hunting changes our perspective on their interactions,” stated Sarah Fortune, a researcher and assistant professor at Dalhousie University, who led the study published in Scientific Reports.
The research team utilized drone and underwater footage, attaching cameras and hydrophones to the orcas for detailed observation. Their recordings demonstrated that the orcas would pursue the dolphins at the surface, and also follow them during dives, reaching depths of up to 60 meters (197 feet) to catch Chinook salmon.
Despite low light conditions underwater, the cameras captured the orcas catching salmon, with sounds of crunching prey audible through the hydrophones. They eavesdropped on the echolocation clicks of both dolphins and orcas, which are crucial for navigation and environmental awareness.
Data revealed 258 instances of interactions between dolphins and orcas from August 15 to 30, 2020, indicating that all whales involved engaged in hunting and eating salmon. This suggests that the killer whales may be using the dolphins as scouts to locate the fish more efficiently.
Interestingly, while the orcas benefit from this cooperative behavior, it is likely that dolphins gain protection from potential threats, such as other orca groups that hunt dolphins. Observations indicate that dolphins may initiate these encounters, raising questions about the dynamics of such interactions.
