Question of optics: To err is human, to mistakenly bite is baby white shark

Baby white sharks learn to hunt on the fly. Though months-old pups feast on fish and other small fry, older juveniles are finally big enough to tackle seals and other meatier meals. It might seem easy to spot a blubbery seal in the waves.
Question of optics: To err is human, to mistakenly bite is baby white shark


But young white sharks have less than stellar eyesight and are also likely colour-blind, rendering the ocean in shades of gray. So you can hardly blame a young white shark for seeing an appetizingly shadowy oval above and chomping. 
For decades, scientists have floated this theory of “mistaken identity” as an explanation behind unprovoked shark bites on humans, which are rare. A paper published Wednesday in the Journal of the Royal Society Interface puts this theory to the test. Based on their simulations of how a juvenile white shark sees the world, they found no meaningful difference between a plump sea lion, a person paddling on a surfboard or even a person paddling on their own — supporting the theory that sometimes, sharks make mistakes. 
Charles Bangley, a marine ecologist at Dalhousie University in Nova Scotia who was not involved with the research, said the paper supports common sense advice for anyone hoping to avoid being bitten by a shark: Swim in calm, clear water away from seals and other prey. Catherine Macdonald, a lecturer at the University of Miami and the co-founder of the marine science program Field School, said the study was “well-executed” and opened up new questions about sharks and people. 
“Does it make a difference if it’s an honest mistake?” Dr. Macdonald said. “We can’t tolerate those risks to people regardless.” Baby white sharks are blissfully unaware of the bad rap they are born into. “White sharks have been described as these mindless killers,” said Laura Ryan, a neurobiologist at Macquarie University in Australia and an author on the paper. But she hopes they may begin to be seen “in another light by understanding their world.” White sharks, along with bull sharks and tiger sharks, are responsible for most injuries and fatal bites to humans — who are most often surfers. And the most frequent biters appear to be juveniles, between eight to 10 feet long. But white sharks usually release a person after the first bite, which may suggest they do not actively hunt humans as prey. “As a general rule for shark bites, the vast majority of them are one and done,” Dr. Macdonald said. 
Though mistaken identity theory made logical sense, it would seem easily debunked on the basis of our own visual perception: The average sighted person could likely distinguish between the silhouette of a surfer and a seal paddling side-by-side. Recent investigations into shark vision have expanded scientists’ understanding of how the cartilaginous predators see their environment: probably in grayscale and with a minimal ability to see detail. To try and see the world as a shark, Dr. Ryan said to imagine taking your eye examination underwater without goggles — things are a little less sharp. As such, the visual cues a hunting shark most relies on are probably motion and brightness contrast. 
The study suggests young sharks must be using other tactics to distinguish between people and prey, Dr. Macdonald said, adding that the number of people in the water has increased significantly in recent years without an associated spike in bites. “They eat seals everyday and bites on people are incredibly rare,” Dr. Macdonald said. “So if they’re not solving the problem visually, then how do we think they’re solving it?” If the answer lies with a shark’s other senses, such as scent, this could determine what interventions would make sense to prevent encounters in the wild, she added. 
Imbler is a journalist with NYT©2021 
The New York Times

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