2/28/2023 0 Comments Great white shark predators![]() ![]() Scientists are not sure how the sharks detect the orcas. The sharks' willingness to give up good feeding opportunities at the Farallon Islands suggests that going elsewhere is preferable to sticking around and facing the risk-however slight-of becoming an orca's next meal. “There's a lot more feeding habitat for white sharks because the rookeries are expanding,” thanks to intensive conservation efforts, says ecologist Chris Lowe of California State University, Long Beach, who was not involved with the new study. The eastern Pacific great whites do have other hunting grounds. Either way, this extreme caution may simply be a prudent survival strategy for the sharks.Īn orca ( killer whale) feeding on herring. It is not clear whether the sharks avoid orcas out of fear of getting eaten or because they compete over the same seal prey. At least one orca has been observed killing and eating an adult white shark at the Farallon Islands, back in 1997. Some orcas specialize in eating salmon and other fish others prefer pinnipeds (a group that includes seals and walruses), and a third type feasts on sharks. “One of those tricks is knowing when to fold.” What was particularly surprising to him is that it can take almost a full year before the sharks feel comfortable returning. “For sharks to have survived and thrived in our ocean for so long, they have their bag of tricks,” Jorgensen says. Sharks have existed for at least 450 million years, whereas cetaceans (whales and dolphins) evolved just 50 million years ago. The findings were described in a study published in April in Scientific Reports. Researchers recorded a fourfold to sevenfold reduction in the number of elephant seals killed by great white sharks during years in which they were scared away. And the sharks do not just disappear for a day or two-they stay away for the entire season. Great whites have been seen abandoning this prime feeding area when killer whales come too close for comfort-even if the mammals are simply passing through for a few hours. Jorgensen and his colleagues drew this conclusion in a recent study that combined their shark-tagging data with a nearly three-decade survey of wildlife abundance around Southeast Farallon Island. ![]() “Normally the sharks hang around for weeks or months at a time.” So why did they flee? Great white sharks are perhaps the most widely feared predators in the ocean, but it turns out they may have something to fear, too: orcas, also known as killer whales. Not just one or two but all 17, in a matter of hours,” Jorgensen recalls. But something odd happened one autumn: “In 2009, 17 of those tagged white sharks were simultaneously swimming around the Farallon Islands, when they abruptly departed. The senior research scientist from the Monterey Bay Aquarium and his team have attached tracking tags to 165 of the toothy predators, which routinely visit islands west of San Francisco and prey on elephant seals. Salvador Jorgensen has spent more than 15 years studying great white sharks near California's coast. ![]()
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