Shark attacks are rare.
Sharks that attack surfers or bathers have such poor eyesight that scientists have concluded that they mistake them for their usual prey, such as seals or sea lions, according to a study released Wednesday.
“From the point of view of a great white shark, neither movement nor shape allows an unequivocal visual distinction between pinnipeds and humans,” write the authors of the article published in Interface, a journal of the Royal Society, noting that their work “supports the misidentification theory” to explain certain attacks.
“It is the first study to analyze this theory from the visual point of view of a white shark,” he tells the AFP its main author, Laura Ryan, a biological sciences researcher at Macquarie University in Australia.
Shark attacks are rare (less than sixty in the world in 2020), according to a specialized department at the University of Florida in the United States. But they keep alive, according to the study, the “disproportionate” fear associated with ignorance about the animal’s motivations, especially when the attack occurs without apparent provocation.
The white, tiger and sardinian sharks are the ones that most attack surfers.
If the white shark is known to detect sounds and smells at a great distance, it is assumed that up close it relies mostly on its sight to identify and attack its prey.
Insensible al color
The problem is that the shark’s visual system is almost insensitive to color and has a very poor ability to distinguish the details of a shape. Its resolution, up to six times lower than that of a human being, is even worse in young white sharks, which represent the greatest risk of bites for surfers, according to the study.
To test the misidentification theory, Macquarie’s team made “videos taken from the point of view of the shark and processed them with a program to mimic” its visual system, and in particular its ability to distinguish a shape and its shape. movement, explains the scientist.
To do this, they recorded from the bottom of a pond images and videos of a sea lion, a delicacy for the scrawny one, which would pass near the surface a few meters above a shark.
They then compared their shapes with those of swimmers or surfers who paddle, with or without leg movement, on the three main types of surfboards according to their size.
From the point of view of a young white shark, the movement signals of a swimmer or those of a surfer aboard his board are almost impossible to distinguish from those of a pinniped, according to the study.
In principle, visibility at sea would be less than in the pond used for the experience.
In terms of shape, a pinniped with folded fins looks more like a swimmer or surfer on a small board than a pinniped with open fins. “Large boards are less like” a pinniped, according to Ryan, who nevertheless clarifies that “there have been incidents of biting on large boards.”
Now the researchers are going to try to determine if a “change in the visual signals of potential prey would be an effective protection technique against white sharks,” continues the scientist.
The solutions have to “not only prevent shark bites” but also “not endanger other marine species.” (I)
Paul is a talented author and journalist with a passion for entertainment and general news. He currently works as a writer at the 247 News Agency, where he has established herself as a respected voice in the industry.
