Bright lights on surfboards keep great white sharks away. If you’re a surfer who doesn’t want to be attacked by great white sharks, your surfboard should be as dark and stealthy as possible, right? Maybe not, as a new Australian study suggests, a lighted board may actually be better at keeping sharks away.
For some time, it has been believed that great white sharks attack surfers because, when seen from below, the silhouette of a surfer on a board is very similar to the silhouette of one of the shark’s main prey animals, seals. . So it stands to reason that if you can visually break the silhouette of a surfer, it won’t look like a seal. To that end, some scientists have experimented with surfboards that have black and white stripes underneath them. The problem is that when viewed against a bright sunny sky background, these boards still present a fairly solid dark silhouette.
One animal that avoids this problem is the navigator fish. The fish evades predators by means of glowing glandular organs on its underbelly known as photophores, which break its silhouette even against a bright background. Inspired by ocean fish, a team led by Dr Laura Ryan and Professor Nathan Hart from Macquarie University decided to investigate whether LED lights could do the same for surfers.
In several experiments conducted over six years in South Africa’s Mossel Bay, Ryan and his colleagues towed seal-shaped foam lures on the surface of the water, 20 meters behind a boat. When these baits were released in their original form, great white sharks, which are common in the area, regularly attacked them from below.
However, when the underside of the prey was completely covered with LED light, attacks were greatly reduced. South African authorities did not allow the team to experiment with real surfboards, fearing that it would encourage local sharks to attack the real surfboards.
Of course, covering the entire underside of a surfboard with LEDs would be too expensive and impractical for real-world use. Due to this limitation, scientists experimented with different patterns of light. Finally, it was found that spaced strips of LEDs placed across the underside of the bait were most effective in preventing attacks.
Ryan and Hart now plan to test a prototype board with embedded LED strips. Among the things they want to investigate is the effect of the lights when the board is not moving, as well as their effectiveness in deterring attacks by shark species other than great whites. “It’s like an invisibility cloak, but we break the object, the visual silhouette, into smaller pieces,” says Professor Hart. “It’s a complex interaction with shark behavior.”
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