A new study in Current Biology reveals that light-based strategies could potentially reduce shark attacks by disrupting their ability to identify prey. Led by Professor Nathan Hart, head of Macquarie University’s Neurobiology Lab, and Dr Laura Ryan, the research explores how modifying the visual silhouette of objects can trick a shark’s visual system. The findings offer a promising foundation for non-invasive technologies to protect surfers and swimmers.
Great white sharks rely heavily on their eyesight to hunt, lunging upward to seize prey like seals. While their vision is effective at detecting silhouettes against the light surface of the water, it is limited in detail, as sharks are likely colour-blind and have poor visual acuity. This inability to differentiate a surfboard or human from a seal makes sharks a danger to people in the water.
Inspired by juvenile plainfin midshipman fish, which use natural light to obscure their silhouettes and evade predators, the researchers applied a similar concept to deter sharks. Using counterillumination, they tested how strategically placed lights could break up an object’s silhouette, making it harder for sharks to recognise as prey.
Dr Ryan conducted the experiments over six years in Mossel Bay, South Africa, a known hotspot for great white sharks. Foam seal-shaped decoys were towed behind a boat to attract sharks. By attaching LED lights in specific configurations, the team was able to disrupt the decoys' silhouettes. Lights arranged in stripes perpendicular to the decoys’ movement proved particularly effective, significantly reducing shark bites.
Professor Hart explains, “It’s like an invisibility cloak, but instead of hiding the object, we break the silhouette into smaller parts. The pattern and brightness of the lights must be carefully calibrated to influence the shark’s behaviour.”
The study offers an innovative approach to shark deterrence, leveraging an understanding of their visual system. This light-based method could pave the way for safer ocean activities without harming marine life. As researchers refine this technology, it holds the potential to save lives and foster coexistence between humans and sharks.