‘Invisibility cloak’ for surfers: Researchers find new solutions to keep

Scientists have found that equipping surfboards with bright LED lights could deter great white shark attacks on surfers and swimmers. A recent study published in the journal Current Biology found that lighting the underside of surfboards disrupts the silhouette perceived by sharks, making them less likely to mistake humans for their usual prey, such as seals.

The research was led by dr. Laura Ryan, a biologist at Macquarie University in Sydney, Australia, who specializes in comparative neurobiology and is herself an avid surfer. Dr. Ryan, along with Professor Nathan Hart, head of Macquarie University’s School of Natural Sciences, spent six years conducting experiments in the waters of South Africa’s Mossel Bay, a popular feeding ground for great white sharks.

Great white sharks often attack their prey from below, and due to their much lower visual acuity compared to humans, they can easily mistake the silhouette of a surfer or swimmer for that of a seal. “There was a big series of shark bites and as a really keen surfer I was spending a lot of time thinking about seeing sharks,” said Dr. Ryan. She started thinking about how her research on shark vision could be used to protect people from shark attacks. “I started to think if what I was learning could protect surfers?” she added.

To test their theory, the research team towed seal-shaped decoys equipped with various LED light configurations behind a boat in waters known to be inhabited by great white sharks. They experimented with different light treatments on the lures, including dim, intermediate and bright LED lighting, as well as different patterns such as horizontal and vertical stripes, continuous lighting and strobe effects.

The study found that brighter lights on the underside of the lures were more effective at deterring great white sharks, with the brightest lights being the most effective. Non-illuminated lures were attacked or followed by sharks more than any of the illuminated lures, indicating that brighter lures resulted in less interaction. “The most important thing was that the brightness of the decoy had to be brighter than or equal to the background light. As long as the lighting kept the silhouette from looking black, it seemed to work,” explained Dr. Ryan.

Horizontal strips of LED lights have proven to be particularly effective in breaking up the silhouette of baits, making them look less like shark prey. “When you do horizontal stripes, the silhouette (appears) wider than it is long, so it’s less like a seal,” said Dr. Ryan. In every instance where the striped design was used on lures, there were no strikes. The vertical lights, however, were less effective, possibly because they broke the silhouette into longer sections that could still be identified as a seal.

The research team also found that strobe lighting was less effective than continuous lighting because it gave the sharks a momentary glimpse of the lure’s silhouette, leading to increased interaction with the objects. “Interestingly, just that little glimpse of the whole silhouette was enough for great white sharks to start biting the baits,” noted Dr. Ryan.

Professor Nathan Hart commented on the findings, saying: “It’s like an invisibility cloak, except we’re breaking the object, the visual silhouette, into smaller pieces.” He added: “So we think this tells us a lot about how sharks see the world and how they detect and target their prey. But potentially it also gives us insight into how we can develop a non-lethal deterrent to sharks, especially for surfers. “

Researchers are now in the process of building prototypes for use on the underside of kayaks and surfboards, including embedding LEDs into surfboards. “What we’re trying to do now is go from seal baits to a surfboard prototype by embedding LEDs into the bottom of a surfboard,” said Dr. Ryan. She stressed the importance of practicality, stating, “As a surfer, I want it to be usable.”

Further research is needed to determine whether the light deterrent is effective on other shark species, such as bull sharks and tiger sharks, which have different hunting strategies and may not rely on visual cues in the same way much like the great whites. “We don’t know if it will be as effective on them because we’re not sure if they rely on visual cues as much as white sharks,” said Dr. Ryan.

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Globally, the majority of fatal shark bites and attacks are caused by great white sharks, which do not view humans as prey but may mistake them for seals. In Australia, great white sharks have been responsible for 94 of the 255 recorded fatal shark incidents since 1791, according to official data from the Taronga Conservation Society database.

The study’s findings offer a potential non-lethal method to reduce shark attacks on humans without harming the animals. This could reduce reliance on other shark deterrents, such as shark nets and drum lines, which can be destructive to other marine life. By changing the shape of surfboards and other watercraft, surfers and swimmers can safely coexist with sharks in the ocean.

Sources: Mundo, La República, La Croix, France 24, Asharq Al-Awsat (English), Manila Times, Tuu1ed5i Tru1ebb News, Sky News Arabia, ORF Science, The Guardian, New Scientist, ABC News Australia, Gazeta.ru, Sydney Morning Herald, The Age

This article was written in collaboration with generative AI company Alchemiq