By Jordan Baker
As a surfer and shark expert, Laura Ryan has spent much of her career pondering how to safely keep her two great passions apart.
Most shark-fighting strategies involve stopping the animal with nets or electric currents. What if she could work out a way to stop them from taking an interest in humans in the first place? To find that solution, she’d have to climb into the mind of a hungry great white.
The Macquarie University biologist studied the behaviour of white sharks towards their prey and found evidence to support the theory that they attack because they confuse surfers with seals. A shark’s eyesight is too poor to determine colours or detail; all it sees is grey, blurry silhouettes.
If surfers could use light to change the shape of their silhouette from below, she figured, the sharks might just swim away. Then there may be less need for drum lines, which can be destructive to other marine life, or intensive patrols over long stretches of beaches.
To test their theory, Ryan and her colleague, Professor Nathan Hart, travelled to South Africa, renowned for its population of great white sharks. They cut boards from the silhouette of a real seal, covered them in lights of different patterns and brightness, hurled them into shark-infested waters and waited for a great white to pounce.
Kai McKenzie lost his leg in a shark attack mid-year. In October, he was back in the ocean.Credit: Instagram
After several trips, they found their answer; the right combination of lights can trick sharks into seeing a shadow that’s far shorter than a seal. “On our best-performing boards and patterns, we didn’t get any white shark bites at all,” said Ryan, whose research is being published in the journal Current Biology on Tuesday.
Last year, Australia had the world’s most shark-related deaths, claiming four of 10 fatal attacks. Of 69 shark attacks in 2023, more than 40 per cent of which involved surfers, 15 were in Australia.
A great white killed a diving instructor, Simon Nellist, off a Sydney beach in late 2022, and in July, rising surf star Kai McKenzie lost his leg after an attack by a great white, which he fought off before catching a wave to shore (he returned to the surf in October; “Ya ain’t never gunna take me away from the ocean,” he wrote on Instagram).
Macquarie University researchers tested boards shaped like seals to see if they could trick sharks with light. Credit: Macquarie University
NSW has one of the world’s most comprehensive shark management projects, with 305 SMART drumlines (sharks are intercepted, tagged and relocated), nets at 51 beaches, and drone patrols at 50 beaches during holiday seasons. But they can’t protect all surfers at all beaches, particularly remote ones.
The next step for scientists is to develop a prototype of a board that’s not too heavy for surfing, kayaking or stand-up paddleboarding. They’ll test those too – although not with real surfers.
“We go through a lot of animal ethics and human ethics [approval],” said Ryan. “My fieldwork team is OK with me being on the boat, but that’s about as close as I’ll get to the water.”
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