Caribbean Reef Sharks Prefer to Sneak Up on Prey--And Humans

Not only do sharks have rows of teeth, not only are they fast, but now it turns out that they're also highly intelligent when it comes to hunting their prey. Scientists have discovered that sharks can comprehend body orientation and know when a human is facing them or not, which allows them to approach stealthily from behind.

In order to hunt successfully, a predator needs to correctly perceive the body form, size and movement of its potential prey. This also seems to be the case when sharks seek out food. When a shark encounters a potential meal, it prefers to sneak up from behind and avoid the prey's field of vision. Yet until now, scientists have been unsure whether a shark could identify human body orientation and then use the information in a self-serving manner.

In order to find that out, the researchers conducted a series of tests. They developed an experiment to evaluate if sharks showed a measurable preference based on body orientation when approaching a person, and if they chose a certain swim pattern when close to a human being. In one of these experiments, 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.

So what did the scientists find? It turns out that when approaching a single diver, the sharks preferred to swim outside the person's field of vision. This indicated that the sharks could identify human body orientation.

"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," wrote Erich Ritter, one of the researchers, in a news release.

The findings are published in the journal Animal Cognition.