Great white sharks (Carcharodon carcharias) are often unfairly the stuff of marine nightmares. But these infamously fearsome creatures are sometimes eaten by an animal even higher on the food chain—orca whales (Orcinus orca), also known as killer whales.
As far as we know, these cetaceans are the sole predator that can kill a great white, Charlie Huveneers, director of Flinders University Marine and Coastal Research Consortium in Australia, tells Popular Science.
This predator relationship was particularly emphasized in 2015, when passengers on a cage-diving boat at Australia’s Neptune Islands witnessed a group of orcas presumably kill a great white shark. After this event, white sharks in the region disappeared for approximately two months. Many people blamed killer whale predation and pointed to comparable situations in South Africa. In fact, researchers believe that episodes of this sort make sharks suddenly leave gathering sites along coasts, with some papers proposing that these disappearances can occur for stretches of weeks to months, if not more.
“The sudden disappearance of white sharks following killer whale predation, or even presence, has been observed across different locations, including in South Africa or California,” Huveneers explains.
However, a recent study published in the journal Wildlife Research and co-authored by Huvaneers, suggests that orcas aren’t always behind these events. The team investigated shark disappearances by studying over a decade of acoustic tracking data and tourism sighting records. This long-term timeline stands in stark contrast to earlier research, a majority of which depended on observational data.
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“Our research shows that long absences can happen naturally, even without killer whales present. Across 12 years, we recorded six long absences, and only one coincided with killer whales,” he says.
Their work also demonstrates that “killer whales aren’t always, or the only, driver of long white shark absences.” In other words, the Neptune Island disappearance may have been natural rather than triggered by the predation event. The longest of their noted absences—which lasted more than the Neptune Island event—took place without any known killer whales. In fact, killer whale presence and shark deaths lead only to short-term disappearances.
Huveneers adds that short-term shark departures can be caused by other factors, including shared environmental cues and chemical signals such as necromones, which a shark releases when it dies.
“This study highlights the importance of long-term monitoring to understand white shark movements and site fidelity, while challenging the idea that killer whales are always or solely responsible for prolonged shark absences,” Lauren Meyer, a marine scientist at Flinders University and co-author of the paper, concluded in the statement.
Moral of the story, shark disappearances are not always the fault of killer whales—these big fish might just be doing their own thing.
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