Sharks can tell a person is facing them, prefer to come up from behind

NEW YORK, Dec. 5 (UPI) -- Sharks can tell whether humans are facing them, which may explain their preferred technique of attacking their prey from the blind side, U.S. researchers say.

Sharks can comprehend human body orientation, Erich Ritter of the Shark Research Institute and Raid Amin of the University of West Florida report in the journal Animal Cognition.

To hunt successfully a predator needs to correctly perceive the body form, size and movement of its potential prey, and a shark's approach to typical prey, as well as humans, indicate these predatory fish prefer to avoid the intended victim's field of vision, Ritter and Amin said.

In experiments using scuba divers and Caribbean reef sharks -- not considered to be a dangerous species for humans -- significantly more sharks preferred to swim outside the person's field of vision, they said.

The results suggest sharks can identify human body orientation, although the mechanisms used and factors affecting the nearest distance of approach remain unclear, they said.

"Our discovery that a shark can differentiate between the field of vision and non-field of vision of a human being, or comprehend human body orientation, raises intriguing questions not only about shark behavior, but also about the mental capacity of sharks," Ritter said.

"The more research is conducted on how sharks sense and interpret humans, the better we will understand how to cope with them in their habitat,"Amin added.