Water snakes startle fish to make them flee into their jaws

June 19th, 2009 - 12:46 pm ICT by ANI  

Washington, June 19 (ANI): A tentacled snake from South East Asia has developed a unique line of attack to catch its prey-it startles a fish in a way that the prey turns toward the snake’s head to flee instead of turning away.

In fact, the fish’s reaction is so predictable that the snake, instead of tracking its movement, actually aims its strike at the position where the fish’s head will be.

“I haven’t been able to find reports of any other predators that exhibit a similar ability to influence and predict the future behaviour of their prey,” said Kenneth Catania, associate professor of biological sciences at Vanderbilt University.

Catania used high-speed video to deconstruct the snake’s unusual hunting technique.

“Before I begin a study on a new species, it is my practice to spend some time simply observing its basic behaviour,” he explained.

While fishing, the snake forms an unusual “J” shape with its head at the bottom of the “J”.

It remains completely motionless until a fish swims into the area near the hook of the “J” and that’s when the snake strikes.

The snakes’ motions take only a few hundredths of a second, and are too fast for the human eye to follow, but its prey reacts even faster- in a few thousandths of a second.

The studies have found that many fish have a special circuit in their brains that initiates the escape, which biologists call the “C-start”.

Fish ears sense the sound pressure on each side of their body. When the ear on one side detects a disturbance, it sends a message to the fishes’ muscles causing its body to bend into a C-shape facing in the opposite direction so it can begin swimming away from danger as quickly as possible.

When Catania began examining the movements of the snake and its prey in slow motion, he saw something peculiar-when the fish that the snake targets turn to flee, most of them turn toward the snake’s head and many literally swim into its jaws!

After a closer study of the snake’s actions, he found that when the snake strikes, it doesn’t aim for the fish’s initial position and then adjust its direction as the fish moves - the way most predators do.

Instead, it heads directly for the location where it expects the fish’s head to be.

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

The study has been published in the online early edition of the Proceedings of the National Academy of Sciences. (ANI)

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