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While it seems obvious that swimming in a stinking cesspool of rotting whale flesh, blood, and other bodily fluids near a beached whale is a bad idea, researchers have discovered one more reason why you wouldn’t want to: great white sharks are attracted to the gory mess, and act erratically in its vicinity.

“I would never recommend jumping in the water next to a whale carcass,” says James Tucker, a marine science graduate student at Southern Cross University in Australia.

Though not exactly everyday life advice, the insight that great white sharks behave differently near the rot of a beached whale is valuable information for conservationists, tour operators, and others concerned with the well-being of sharks and people. It has implications for how beached whales, and water users, should be managed.

Thanks to decades of conservation work, populations of some whales are on the rise. But this success is causing new challenges, Tucker says—more whales means more whales eventually die and wash up on beaches. Aside from smelling and being a potential eyesore, these carcasses are also attracting scavenging sharks, which raises fears that they could pose a danger to people nearby.

Tucker and his colleagues wanted to assess the risk by studying how sharks behave around beached whales. Using drones, the scientists closely followed great white sharks off the coast of New South Wales, Australia, in 2018 and 2019. They tracked 55 sharks in the water adjacent to whale carcasses, and compared their behavior to footage of 108 sharks swimming in water with no dead whales.

The research showed that there is an appreciable change in the behavior of great white sharks when a beached whale carcass is nearby.

Drone footage revealed that great white shark behavior is different in the presence of a beached whale. Video by James Tucker

Analysis of the drone footage showed that when there is no dead whale in the vicinity, great whites have fairly predictable behavior, cruising along the beach at a more or less even speed.

But the situation changes near a whale carcass. There, great whites tend to be larger on average—possibly because bigger sharks are muscling out their smaller competitors—and to be swimming more quickly. The sharks also change their behavior. “These sharks were circling, staying around the area where the food source was,” Tucker says.

Tucker’s team studied white sharks, as they are large and easy to track by drone. While the scientists don’t have before and after footage from the beaching sites, Tucker speculates that there are likely more sharks in the water near a beached whale than elsewhere.

“I think this is a great little paper,” says Stephen Kajiura, a marine biologist at Florida Atlantic University who was not involved in Tucker’s study. “This is something people have suspected for a long time, but it’s great to see it quantified.”

As to whether the lure of a whale carcass leads to an increase in shark attacks on people, the data is less clear. While white sharks are responsible for a high number of conflicts with humans relative to other sharks, the closest known attack near a beached whale carcass took place several kilometers away from the dead whale and is definitely not a smoking gun, Tucker says. Nonetheless, he says beached whales should be managed closely. There is also some risk to workers removing carcasses if they have to enter the water to do so.

“You should remove [the carcass] as quickly as possible,” he says. “We recommend a beach be closed as soon as a stranding occurs, before it even hits the beach.”

Kajiura says the problem is that big scavenger sharks like great whites, tigers, or bulls aren’t picky eaters. If they are hungry for the rotting flesh of a whale, but can’t access it because the water is too shallow or the carcass is on the beach, potential problems could occur if humans are in the mix.

As an example of where this knowledge could prove particularly valuable, Tucker says he has seen some unscrupulous tour operators in Australia bringing divers to floating whale carcasses to swim with the sharks, putting both humans and sharks at risk.

“I’m all about diving with sharks, but I don’t think that’s the right situation to do it,” he says, adding that if humans do get bitten, it leads to more problems for sharks.

“The biggest fear is that someone gets hurt by a shark, then sharks themselves get persecuted,” Tucker says. “People want to hunt down sharks as soon as they hear the story that someone was hurt by a shark, and they don’t take into account the situation that was happening before that attack occurred.”