Australian researchers have been towing seal-shaped decoys in waters infested with great white sharks for years, and have found that wrapping the lures in very bright light (like an aquatic Christmas tree) can be effective at repelling sharks. I concluded that there seems to be.
That’s because sharks are used to seeing the dark silhouette of their prey from below, backlit by the sun.
So when a fake seal’s body is wrapped in bright horizontal stripes of LED lights, the silhouette appears to be shredded so that it no longer looks like a seal, said researcher Nathan Hart, dean of the School of Natural Sciences at Macquarie University in Sydney.
Hart and biologist Laura Ryan, one of the co-authors of a study recently published in Current Biology, installed a similar pattern of LED lights on the bottom of surfboards to reduce the risk of shark attacks. We are planning to see if we can reduce this.
“Surfing for me is a really peaceful place. It’s being in nature. It’s doing what I love,” Ryan said. She’s hopeful that technology might help make this world a little more peaceful.
Although incredibly rare, scientists have come up with technological solutions to threats that still play in the back of the minds of many ocean enthusiasts, like the eerie theme of “Jaws.” This is not the first time I have explored this.
Previous researchers have tried to disrupt sharks’ electroreceptors using devices that emit electromagnetic fields. Some people have tried bracelets that emit an odor that, in theory, sharks don’t like. Additionally, some companies are selling black-and-white striped wetsuits based on a similar theory to that behind LED lights: disrupting the prey-like silhouette.
But Chris Lowe, a marine biologist and director of the Shark Research Institute at Cal State Long Beach, has not read the new Australian study, but for decades all the data on such shark repellents has been “It’s vague,” he said.
Previous devices seemed to work about 40% to 50% of the time. “If your goal is to be more confident in the water and you can afford it, that’s great,” Lowe says.
But he worries that some people may feel invincible when wearing such things, as if they were wearing a “Superman cape.” And they end up surfing where sharks typically feed, putting them at higher risk.
“I always rely on the old litmus test for birth control,” Lowe said. “Would you be satisfied with a contraceptive that only works 40% of the time?”
One problem with devices designed to essentially make humans invisible to sharks is that vision is not the only tool sharks use to detect prey. Sharks also use their sense of smell and the ability to detect vibrations in the water.
“How important is it that the shark can’t see you when it can still smell you and feel you?” Lowe asked.
Whatever sensory input sharks use to track us, the truth is that they’re not that interested in humans. Since 2000, millions of people have waded in the waters off California’s coast, but the state Department of Fish and Wildlife has recorded only 127 shark incidents. An “incident” is when someone approaches a shark and is touched, or when a shark touches a surfboard, paddleboard, or similar means of transportation.
It’s safe to assume that everyone who experienced such an incident was truly freaked out, but only 51 people reported physical injuries. And only eight people were killed by sharks. At least seven of those deaths were caused by great white sharks. In other cases, the species is unknown.
You are more likely to die from lightning.
Australian scientists traveled to Seal Island off the coast of South Africa to conduct a six-year study. Seal Island has been the setting for countless Shark Week episodes and YouTube videos celebrating the spectacular sights and shocking violence of great white shark attacks. From the depths of the ocean, and in the grip of its mighty jaws, the fateful seal breaks through the surface.
During the research process, the team learned that lighting placement and intensity are important. When hung vertically along the length of the false seal’s body, the light does not have much of an effect to disrupt the silhouette seen from below. And the light needs to be bright enough to counteract the effects of the sun shining from above.
Scientists have discovered that to achieve optimal “backlighting”, artificial light must be brighter than the background light.
“If we don’t get this right, it may not be effective,” Hart says.
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