Bright lights from surfboards may keep great white sharks away

If you’re a surfer who doesn’t want to be attacked by a great white shark, your surfboard should be as dark and inconspicuous as possible…right? Probably not, as new Australian research suggests that illuminated boards may actually be more effective at keeping sharks away.

For some time, it has been believed that great white sharks attack surfers. Seen from below, the silhouette of a surfer on a board closely resembles that of a seal, the shark’s main prey.

So it stands to reason that if you can visually break up the surfer’s silhouette, it will no longer look like a seal. To this end, some scientists have experimented with surfboards with white and black stripes on the underside. The problem is that these boards still exhibit a relatively solid dark silhouette when viewed against a bright, sunny sky.

One animal that can avoid this problem is the plainfin midshipman fish. They evade predators through an underside luminescent gland organ known as a luminophore. Luminous pores lose their silhouette even when viewed against a bright background.

Inspired by this fish, a team led by Macquarie University’s Dr Laura Ryan and Professor Nathan Hart set out to see if LEDs could have the same effect on surfers.

In multiple tests conducted over six years in Mossel Bay, South Africa, Ryan and his colleagues towed a foam decoy shaped like the silhouette of a seal across the water 20 meters (66 feet) behind a boat. When these decoys were left in their basic form, they were regularly attacked from below by great white sharks, which are common in the area.

However, when the underside of the decoy was completely covered with LEDs, the attacks were significantly reduced. South African authorities did not allow the team to experiment with actual surfboards, as it could encourage local sharks to target surfboards in general.

Of course, covering the entire underside of a surfboard with LEDs would be too costly and impractical for real-world use.

With this limiting factor in mind, scientists experimented with different patterns of light. Ultimately, a spaced stripe of LEDs running across the underside of the decoy proved to be most effective at deterring attacks.

macquarie university

Ryan and Hart now plan to test a prototype board with embedded LED stripes. Among other things, they want to see how effective the lights are when the board is not moving, and how effective they are at preventing attacks by shark species other than great whites.

“It’s like an invisibility cloak, except it’s breaking up the object, the visual silhouette, into smaller parts,” Professor Hart says. “This is a complex interaction with shark behavior.”

A paper on this research was recently published in the academic journal Current Biology. In the video below, you can see a shark attack a seal decoy.

Source: Macquarie University