Orcas are increasingly helping themselves to fishers’ catches, impressing researchers with their innovation and ticking off fishers. A new paper published in the journal Biology Letters examined how two different orca populations in the Indian Ocean have altered their feeding to take advantage of human activities.
Interaction between killer whales and commercial fishers near the Crozet Islands has grown since the 1990s. This area is a top place for catching Patagonian toothfish, also known as Chilean sea bass. Fishers use longlines baited with many hooks stretched over the ocean floor to catch the toothfish. For orcas, this makes a convenient buffet.
Data from 2003 through 2018 records incidents of orcas helping themselves to fish caught on longlines and reveals how this behavior — scientists call it depredation, killer whales call it lunch — increased over time. In one of the orca populations studied, scientists noted that individuals had eaten fishery catches as far back as 1996. This behavior spread through the pod, with all the orcas raiding longlines by 2014.
“This study is illustrative of how human activities, by altering the availability of resources in ecosystems, may lead to new behaviors spreading across individuals of species capable of innovating in response to changes in their environment,” the study authors wrote.
However, orcas may not be snatching fish just because it’s easier than hunting. Overfishing may be the true culprit. The toothfish population declined in the 2000s, putting humans and orcas in direct competition for limited prey. Drama similar to that playing out in the Indian Ocean is also occurring globally. For example, humans and sea lions vie for salmon in the Pacific Northwest, while sharks take fish off lines in Florida.
The scientists’ new study highlights the ingenuity of orcas and the fact that these socially complex beings learn new behaviors from each other.
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