You have probably noticed it if you’ve ever tried to catch a fish using your bare hands or a small net: the uncanny ability of these creatures to escape, sometimes even before you make a move. Most fish species are incredibly fast and seem to be virtual mind-readers when it comes to predicting when and where you will make your next attempt.

The reason behind this remarkable talent is a special circuit present in the brains of many species of fish. Fish ears constantly sense the sound pressure on each side of the body and if the ear on one side detects a disturbance, the muscles of the fish will automatically bend the body into a c-shape facing the opposite direction. This involuntary reaction makes it possible for the fish to start swimming way from harms way as quickly as possible. Scientists call it C-start and it is highly advantageous when escaping from predators. That is, until you venture upon the Tentacled snake (Erpeton tentaculatum) of South-East Asia.

While studying the Tentacled snake, Kenneth Catania, associate professor of biological sciences at Vanderbilt University, realized that this snake has found a way of exploiting the C-start reflex to its advantage.

Using video recordings of snake (see below) and prey Catania was able to slow down the chain of events enough to make them noticeable for a human eye, and what he saw amazed him. Instead of fleeing from the snake, fish would swim right into the mouth of the predator nearly four times out of five. How could this be?

When hunting, the Tentacled snake forms its body into a peculiar J-shape with its head at the bottom of the “J”. It then remains absolutely still until suitable prey ventures close enough to the “hook”-area of the J. When it finally strikes, it rarely misses since the fish seem to be magically drawn to the jaws of their attacker. In 120 attacks carried out by four different snakes, Catania observed no less than 78 percent of the fish turning toward the snake’s head instead of swimming away from it.

Catania also noticed something else: before the snakes moved their head to strike, they always flexed a point midway down the body. A hydrophone placed in the aquarium unveiled that by flexing its body, the snake produces sound waves intense enough to trigger the fish’s C-start reflex, and since the sound comes from a spot opposite the head of the hungry snake, the C-start reflex forces the fish to turn and swim directly towards the snake’s mouth.

“Once the C-start begins, the fish can’t turn back,” Catania explained. “The snake has found a way to use the fish’s escape reflex to its advantage. I haven’t been able to find reports of any other predators that exhibit a similar ability to influence and predict the future behavior of their prey,”

The C-start behaviour is actually so predictable that the snake doesn’t even bother to aim for the initial position of its prey and then adjust its direction as most predators would. Instead, it goes directly for the spot where it knows the fish will be heading.

“The best evidence for this is the cases when the snake misses,” says Catania. “Not all the targeted fish react with a C-start and the snake almost always misses those that don’t react reflexively.”

Kenneth Catania studies the brains and behaviour of species with extreme specializations. His new snake study is published this week in the online early edition of the journal Proceedings of the National Academy of Sciences.