Researchers have filmed orcas bringing down juvenile great white sharks in the Gulf of California. They say this is the first record of killer whales hunting juvenile white sharks in Mexican waters, and the second globally.
To take down their prey, the killer whales flip the young sharks belly up to put them into a state of paralysis called tonic immobility. When the orcas have subdued the shark, they rip out and feast on its energy-rich liver, which is full of nutrients.
Immobilising the shark by turning it upside down likely makes it easier for the orcas to quickly kill their prey and avoid a nasty bite. “The lack of bite marks or injuries anywhere other than the pectoral fins shows a novel and specialised technique of accessing the liver of the shark with minimal handling of each individual,” write the authors in a new paper published in the journal Frontiers in Marine Science.
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This is the same technique killer whales use to hunt whale sharks – the largest fish in the ocean.
“This behaviour is a testament to orcas’ advanced intelligence, strategic thinking, and sophisticated social learning, as the hunting techniques are passed down through generations within their pods,” says the study’s lead author Erick Higuera Rivas, project director at Conexiones Terramar and Pelagic Life.
The killer whales belong to Moctezuma’s pod; a group already known to eat sharks and rays. The researchers wonder whether these orcas are benefiting from warmer waters, which may have changed the distribution of white shark nurseries and lead to more juveniles being present in the Gulf of California where these orcas live.
"Juveniles tend to congregate during their first years in coastal nursery areas making an easy repeatable target,” says co-author Salvador Jorgensen, a marine ecologist at California State University Monterey Bay.
Orcas are known to hunt adult white sharks but juveniles might be easier for them to catch because they haven’t yet learned to avoid the threat of killer whales.
“Adult white sharks have demonstrated an incredible ability to immediately vacate their preferred hunting ground in a mass exodus if orcas appear,” says Jorgensen. “If the juveniles have not yet developed similar anti-predator mechanisms, the white sharks population could become vulnerable.”
Top image: Orca killing young white shark. Credit: Marco Villegas
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