Erich Ritter of the Shark Research Institute and Raid Amin of the University of West Florida said that this ability helps sharks to approach and possibly attack their prey from the blind side - a technique they prefer.
Descriptions of a shark's approach to typical prey, as well as humans, indicate that these predatory fish prefer to avoid the field of vision.
In other words, a shark would tend to approach a person from behind.
These observations underlie the yet-untested assumption that sharks are able to identify human body orientation and can use such information in a self-serving manner.
Ritter and Amin devised a test to evaluate if sharks show a measurable preference based on body orientation when approaching a person, and if they choose a certain swim pattern when close to a human being.
In one experiment, a diver in full scuba gear was positioned on the sea floor in a kneeling position, looking forward. In another, two divers kneeled back-to-back to eliminate the blind area.
They found that when approaching a single test-subject, significantly more sharks preferred to swim outside the person's field of vision.
The results suggest that sharks can identify human body orientation, but the mechanisms used and factors affecting the nearest distance of approach remain unclear.
The study has been published in Springer's journal Animal Cognition.
--ANI (Posted on 06-12-2013)