Sharks may bite humans because they mistake us for seals and sea lions

Researchers believe shark attacks on humans are uncommon, but they do occur when marine predators confuse us with other species.
Sharks might mistake surfers as seals Shutterstock/Dudarev Mikhail

From the perspective of great white sharks, seals and humans look very similar in water. This suggests that shark bites on humans could be mistaken identity.

Shark bites on humans are very rare but they do cause significant and excessive public concern.

We can better understand why sharks bite people to come up with mitigation techniques that are less harmful for sharks and marine life while still being effective for humans, Laura Ryan from Macquarie University in Australia says.

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Ryan and her team made separate video recordings of sea lions and seals swimming in the Taronga Zoos aquarium, Sydney, Australia. They also recorded surfers and swimmers in the tank. A static camera was attached to each tank and looked up. An underwater camera was mounted to an underwater scooter to capture the movements of a great white shark (Carcharodon carcharias), which is one of three shark species that are responsible for human shark bites.

The team used a model of the sharks' visual system to analyse the video recordings. This was done in order to assess the visual similarities of the animals and surfers from the perspective juvenile great white sharks. They are responsible for most shark bites.

The sharks could see no difference in humans swimming, paddling on surfboards, seals or sea lions swimming. Also, the team found that humans and seals looked very similar to surfers and swimmers when their fins were out.

These results show that great white sharks might have difficulty distinguishing humans, seals, and sea lions below. This supports the notion that shark bites can be misinterpreted as cases of mistaken identity.

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This historical negative public perception of sharks as mindless, man-eating creatures has been perpetuated. Ryan says that we are proving that this is not true. They are following their visual system's lead and trying to find potential prey.

Daryl McPhee, Bond University in Australia states: Although we cannot eliminate unprovoked shark biting, our work helps to design further evidence-based visual methods that could reduce the likelihood of white shark bites.

Journal reference: Journal of the Royal Society Interface, DOI: 10.1098/rsif.2021.0533

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