Killer whales teach each other how to steal fish from human fisheries

An international team of researchers has found that orcas are teaching one another how to steal fish and their remains from human fisheries. In their paper published in the journal Biology Letters, the group describes their study of the number of orcas feeding on fish or their remains at human fisheries and whether they are additions to the local environment or the same whales that have learned a new skill.

People working at fisheries have long known that orcas are not afraid to swim into human-populated areas to steal fish from lines or nets, or to eat the discarded remains of fish after they have been gutted. In this new effort, the researchers wondered if such activities have been increasing as orca have found it increasingly difficult to find prey on their own.

The work involved studying the feeding habits of orcas living off the coast of the Crozet Islands, which lie in the southern Indian Ocean. Prior research had shown that the orcas in the area prefer to feed on Patagonian toothfish, and local fishermen and marine scientists have been keeping track of fishing raids conducted by orcas. Noting that such incidents have been on the rise, the researchers wondered if it was due to more orcas making their way to the area to steal the fish, or if more of the same whales living in the area were learning how to conduct such raids.

To find out, they studied pictures taken of the whales by fishermen, scientists and local tourists. They compared the whales in the pictures—orcas have unique color patterns, making it easy to discern one from another. They found little evidence of new whales making their way to the area; instead, it became clear that more of those whales already in the area were learning from those that had already mastered the art of stealing fish from fisheries. More specifically, they found that the number of orcas conducting raids rose from 17 to 43 over the years 2010 to 2017. They suggest not only that more whales are learning to steal fish from humans, but are doing so at an increasing rate.

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