Where Killer Whales and Dolphins Hunt Cooperatively
Roy L Hales/ Cortes Currents - A new study found that Northern Resident Killer Whales and Pacific white-sided dolphins have formed a cooperative hunting relationship to catch Chinook salmon in the Johnson Strait and Queen Charlotte Sound. The dolphins utilize echolocation to locate fish at depth, but their small teeth are designed primarily to grip prey, and they cannot swallow large species like Chinook salmon whole. Instead, dolphins locate the fish, and then wait for the killer whales move in to tear them apart, scattering bits of tissue and flesh into the water.
Dr. Andrew Trites, a professor and director of the Marine Mammal Research Unit at UBC’s Institute for the Oceans and Fisheries, explained, “The dolphins are getting leftovers, but that seems to be reward enough, so there's no competition for what is ultimately killed. Everybody comes out a winner.”
This was the first time Customized Animal Tracking Solutions Tags (CATS) were used on whales and allowed the researchers to collect 3D kinematic data with video and acoustics, continuously recording high-resolution dive data, along with vocalizations and feeding-related sounds.
“ This tag has got a video recorder. It's got a hydrophone. It's listening for all the calls that are being made by the killer whales, but it's also recording dolphin calls as we discover. It has a depth sensor so we know what depth the whale is at. It's got three-dimensional accelerometers. So we can reconstruct all the swimming movements of the whale, whether it turns or heads down or heads up. It does water temperature as well. So it's a very sophisticated fitbit that was designed to be put onto marine life, such as Killer Whales.”
“All of my life I've seen whales from a boat, with a camera in hand or binoculars. Here we're getting a bird's-eye view with a drone, which others have used before, but for the first time, we got the orca eye view of what's really going on, and that changes everything, to see the world as the killer whales experience it.”
Trites suspects but does not know if killer whales and dolphins cooperate in the same manner around Cortes, Read, and Quadra Islands.
“ I don't know how frequently you see white-sided dolphins around Cortes. There is a resident population of white-sided dolphins living in the Salish Sea. I don't know much about their distribution and whether or not those dolphins behave the same as the ones that are up in Johnson Strait and Queen Charlotte Sound. Certainly, the northern residents that are going to your area know how to work with dolphins. The question is whether or not the dolphins in your area know how to hang out and work cooperatively with northern residents.”
Initially, the research team believed these dolphins were harassing Southern Resident Killer Whales, but this perception changed after Keith Holmes, a drone pilot with the Hakai Institute, observed their interactions. He noted, “From above, you could see this incredible amount of activity. It was clear that there was some sort of communication happening, and they were actively foraging together,” as stated in the UBC press release.
Dr. Sarah Fortune, the lead author and Canadian Wildlife Federation Chair in Large Whale Conservation, emphasized the significance of these observations by saying, “We’ve long known that resident killer whales interact with Pacific white-sided dolphins, but seeing them dive and hunt in sync with dolphins completely changes our understanding of what those encounters mean.”