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Snake startles fish right into its jaws

A tentacled snake in captivity.

Fish are masters of escape. In fact, they move so fast it is a wonder that predators can catch them at all.  The mechanism behind a fish’s rapid escape is known at the C-start, and is thought to be a part of a special circuitry in the fish’s brain.  The theory states that “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.” [EurekAlert]

 

While this normally works, the tentacled snake takes complete advantage of the involuntary reaction. The snake lays motionless in the water in an unusual J-shape, with its head at the tip of the J.  When a fish swims by, the snake bends its body, triggering sound pressure waves (you can see slow motion capture of this in the video below at the 40 second mark). Because of the C-start reaction, a fish immediately darts for an escape.  Unfortunately for the fish, that path leads directly into the waiting mouth of the snake. And the technique is fairly reliable. Out of 120 trials, 78 percent of the fish turned towards the snake’s mouth. "Once the C-start begins, the fish can't turn back," Dr. Kenneth Catania says. "The snake has found a way to use the fish's escape reflex to its advantage." [EurekAlert]

 

The story became more astonishing when Catania, recipient of the MacArthur Genius Award, studied the movement of the snake’s head.  Many animals will strike for a prey’s initial position and then adjust to the way the animal moves. However, the snake “heads directly for the location where it expects the fish's head to be.” [EurekAlert]  While this increases a snake’s ability to capture prey, if a fish doesn’t react with a C-start the snake will most likely miss.

 

The next step is to determine whether the behavior is learned or a hard-wired instinct. In order discover the truth of the behavior, Catania, “hopes to obtain some baby snakes that have just hatched and videotape their first efforts to catch prey.” [EurekAlert]

 

This study was published in Proceedings of the National Academy of Sciences.

 

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