Scientists have released incredible footage of northern transient killer whales following Pacific white-sided dolphins to help locate prey, then sharing the catch with them afterwards.
The behaviour was recorded in the waters around Vancouver Island in British Columbia, Canada.
Described in a new study published in the journal Scientific Reports, researchers believe this is the first documented case of cooperative foraging between killer whales (also known as orcas) and dolphins.
Pacific white-sided dolphins, known for their distinctive black, grey and white patterning, are often seen foraging close to northern resident killer whales along the coast of British Columbia, says the study's lead author, Sarah Fortune.
Although killer whales are known for sharing prey with other members of their pods, they typically hunt alone. The fact that the dolphins were seen swimming within metres of them, and the lack of aggression exhibited between the two species, intrigued Fortune and her colleagues. Were the marine animals working together to catch food rather than competing for it?
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To find out more, the team spent the summer of 2020 tracking nine northern resident killer whales around Vancouver Island. They used a range of recording equipment, including drones, underwater cameras and acoustic monitors.
On 25 occasions, the researchers observed killer whales encountering dolphins before veering off course to follow them on foraging dives.
The study suggests the killer whales may be eavesdropping on the dolphins’ echolocation, which they could be using to help detect prey, such as Chinook salmon – the largest species of Pacific salmon.
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The team also documented eight salmon hunts in which killer whales caught, consumed and shared their prey with pod members. Dolphins were present during four of these events. In one instance, the dolphins were seen scavenging the broken-up remains of an adult Chinook salmon, which, when whole, are usually too large for the dolphins to catch and swallow.
The researchers suggest the newly documented behaviour could benefit both species: the killer whales may be using the dolphins’ echolocation to find salmon, while the dolphins gain both protection and food scraps from the killer whales.
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Image and video credits: University of British Columbia (A.Trites), Dalhousie University (S. Fortune), Hakai Institute (K. Holmes), Leibniz Institute for Zoo and Wildlife Research (X. Cheng)
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