Killer whales, dolphins and many other marine mammals thrive through cooperation and community within their pods and schools. Although interspecies interactions have been documented before, the detailed strategies and motivations behind them are often unclear.
Now, for the first time, researchers have observed northern killer whales and Pacific white-sided dolphins hunting together in Canadian waters off the coast of British Columbia. As described in a new article in Scientific reportsThe tagged killer whales appeared to intentionally follow and eavesdrop on the dolphins' echolocation, which led them directly to Chinook salmon, their preferred food source.
So what will this do for the dolphins? In addition to observing killer whales sharing salmon waste with their cetacean cousins ​​after a successful hunt, scientists theorize that large resident killer whales may provide protection for dolphins from predators such as transient killer whales that often hunt them.
Read more: See how killer whales use seaweed as a grooming tool – a surprising find for researchers
Local killer whales are trying to find food
Northern killer whales (Orcinus killer whale) – as the name suggests – are permanently located in one region stretching from southern Alaska to northern Vancouver Island. Unlike their temporary relatives, these killer whales feed almost exclusively on Chinook salmon.Oncorhynchus tshawytscha) as the main food source. But as the Chinook salmon population steadily declines, native killer whales are now listed as endangered in Canada.
Pacific white-sided dolphins (Lagenorhynchus obliquidens), but have a more varied diet, including small fish and squid. Interestingly, they are often seen near resident killer whales without any signs of antagonistic behavior. In fact, they seem to be enjoying each other's company rather than ignoring or avoiding each other.
This has led scientists to wonder if there is more to this relationship. As local killer whales face declining salmon numbers, they may be using their very social and sophisticated hunting abilities team up with an experienced potential companion.
Team up with dolphins to spot salmon
In August 2020, a team of scientists recorded the hunting behavior of nine northern killer whales as they interacted with Pacific white-sided dolphins off northern Vancouver Island.
Dolphins hunt with a pod of northern killer whales.
(Image credit: UBC (A. Trites); Dalhousie University (S. Fortune); Hakai Institute (C. Holmes); Leibniz Institute for Zoo and Wildlife Research (X. Cheng)
They collected data using drone footage, suction cup biotrackers attached to orcas, and acoustic recordings to better understand how the whales hunt when dolphins are nearby.
According to press releaseIn 25 cases, killer whales were guided by dolphins and followed them during dives after meeting them in the water. The researchers also noticed that killer whales reduced their own echolocation in the presence of dolphins.
Since the discovery and capture of Chinook salmon, eight cases of infection by killer whales have been recorded. share remains of salmon with dolphins.
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The study authors interpret the killer whales' decreased echolocation as a deliberate strategy to “listen” for dolphin clicks and calls, potentially helping the whales focus on large Chinook salmon too large for the dolphins to target.
In addition to catching small pieces of salmon, dolphins can gain something even more valuable: safety. By staying close to native killer whales, they can avoid encounters with the transient mammal-eating killer whales that regularly prey on them, but tend to avoid local pods when passing by them. Alliance could also help dolphins avoid great whites sharks which are increasingly migrating to northern waters.
Additional observational studies will be required to confirm this hypothesis. However, these results show how mutual alliances can form naturally in the animal kingdom and how cooperation can improve a species' chances of success.
Read more: Killer whales imitate human speech to communicate with us
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