Every year, there are an estimated average of 63 unprovoked shark attacks around the world, with just five or six leading to death. While the numbers might not be staggering, the fear people have about a “Jaws-” like encounter is very real.
But what if ocean-dwelling humans — namely, surfers — could wear a sort of “invisibility cloak” to stay safe in the deep blue?
Researchers at Australia’s Macquarie University may have discovered just that.
Professor Nathan Hart, head of the university’s Neurobiology Lab, Dr. Laura Ryan, and their colleagues have just published a new study that concludes that humans may be able to trick sharks’ visual systems using one simple technology: LED lights.
The study’s authors have previously discovered that great white sharks heavily rely on their eyes to locate prey and lunge upwards, chomping down on potential food.
Other research has also found that these sharks are likely completely colorblind and have poor "visual acuity,” which is why they often spot their prey based on shape or silhouette.
Unfortunately, that lack of keen vision means sometimes, sharks mistake humans for their natural prey (like seals or large fish).
But Ryan and Hart realized they might be able to use that weakness to their advantage.
They took inspiration from the plainfin midshipman fish, which has a natural defense to produce light and disrupt the shape of its silhouette, deterring predators. This led to the idea of disguising human silhouettes on the surface of the water using lights so that sharks would not mistake them or their surfboards for food.
Their “counter-illumination” strategy was studied over the course of six years at Mossel Bay in South Africa — a notorious great white shark hot spot.
“There’s an island there called Seal Island,” Hart said in a video for the university. “The sharks are there to hunt the seals, and it’s a great place to do this kind of testing.”
Hart and team towed seal-shaped foam decoys on a 20-meter line behind a boat to attract sharks to attack, using LED lights in different configurations to break up the silhouette of the decoys.
“What we found is that if you put lights on the bottom of the decoys, the sharks leave them alone,” Hart continued. “We think this tells us a lot about how sharks see the world and how they detect and target their prey.”
Lights placed in stripes across the bodies of the seal decoys — perpendicular to their movement — were among the most effective deterrents. The brighter the lights, the more sharks were deterred.
“It’s sort of like an invisibility cloak but with the exception that we are splitting the object, the visual silhouette, into smaller bits,” Hart said in a statement.
“It’s a complex interaction with the shark’s behavior. The lights have to be a certain pattern, a certain brightness.”
This research could lead to new designs for surfboards and wetsuits to protect surfers from attacks.
In fact, the team is testing a surfboard prototype with fitted lighting now, according to The Guardian. As surfers themselves, the researchers are hoping to create something practical that doesn’t require too much battery power.
“Surfers can be a little bit fussy with their surfboards,” Ryan told The Guardian. “As a surfer, I want it to be usable.”
Header image courtesy of Macquarie University
