Human swimmers and surfers look very similar to seals to a great white shark swimming below, scientists have found. By analyzing a “shark’s eye view” of the profile of potential prey, researchers found attacks on humans may be the result of mistaken identity.
“I knew there would be some similarities but maybe not to the extent we found,” Laura Ryan, from Macquarie University, Australia, told Newsweek. “Specifically, I thought swimmers might not be as similar as a surfer to a seal as they typically aren’t involved in as many shark bites. However, the swimmers were also difficult to tell apart from a seal.”
Ryan is lead author of a study published in the Journal of the Royal Society Interface that looks at the “mistaken identity” theory of great white shark attacks.
Shark attacks are incredibly rare. In 2020, the International Shark Attack File, run by Florida Museum, recorded 129 shark-human interactions. This included 57 unprovoked attacks, 10 of which were fatal. Three of these were in the U.S., six in Australia and one in Saint Martin.
Great whites are the species involved in most fatal, unprovoked attacks. Most of these are carried out by juvenile white sharks. One theory about why this is is that surfers or people taking part in board sports—who are involved in about 60 percent of cases—look like seals to white sharks swimming below.
To test this idea, Ryan and colleagues simulated “shark vision” using our understanding of the neuroscience of the visual systems of white sharks. They then applied this to the swimming patterns of humans, seals, sea lions and surfers. They compared the different swimming styles, including strokes, and looked at the way each floated and moved through the water. The team then attached a GoPro to an underwater scooter and set to travel at the same speed a predatory shark would swim.
Findings showed huge similarities between all of the entities tested.
“White sharks have to learn what to eat and at around 2.5 [meters; 8 feet] they start to eat seals,” Ryan said. “They need to develop a search image for these prey items and combine that with other sensory information; it’s a learning process that could be prone to mistakes. As they get more experienced though, they may make less mistakes. So not all sharks, and even all white sharks, may bite just because they see a human or seal.”
She said this research was specific to white sharks, and other species may differ: “Sharks also detect smells, sound, electric fields, movement and taste and may be able to tell the difference between humans and seals based on other cues. However, white sharks seem to rely on vision curing prey detection as they are known to bite floats on the surface of the water that don’t produce other sensory cues.”
The team hopes the research will help the development of technology to reduce attacks: “Understanding why shark bites occur can help prevent them,” Ryan said. “In fact, the findings of this study have inspired the design of non-invasive vision-based shark mitigation devices, which are currently being tested.”
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