The acoustic trick of rattlesnakes

Have you ever heard it? Rattlesnakes produce a characteristic sound. It warns of their presence in case of threat. A study shows it has a more complex mechanism than we thought. It’s the rattlesnake’s acoustic trick.

The acoustic trick of the rattlesnakes. Tricking the ear.
The acoustic trick of the rattlesnakes. Fooling the ear.
Measuring the noise

What was the experiment like? They analyzed the warning vibrations of a group of 13 snakes. They were diamondback rattlesnakes from the west, Crotalus atrox. And they came to a conclusion. This reptile is able to vary the frequency of the warning. It does so depending on how far away the potential threat is.

First, the scientists placed moving objects in the laboratory. These approached or appeared to approach the snakes. The reptiles began to shake their tails. At first, the vibration rate increased to about 40 Hz. Then it reached an impressive frequency of between 60 and 100 Hz. Why? It makes its enemies think it’s closer than it really is.

These snakes are very bad-tempered. If you meet one... you'd better leave it alone.
These snakes are very bad-tempered. If you meet one… you’d better leave it alone.
Fooling the neighbors

It’s an unusual mechanism. “It works like a smart signal. It deceives the listener about its actual distance from the sound source. Misinterpreting this thus creates a safety margin in distance.” The lead author of the study, Boris Chagnaud, explains. He works with the University of Graz (Austria).

A simulation was done. They asked a group of 11 volunteers to approach a snake in virtual reality. The snake approached to within four meters. There, the frequency suddenly jumped to 70 Hz. The participants felt that they were only one meter away from the snake. This is how the rattlesnake’s acoustic trick works.

“Snakes don’t just emit sound to announce their presence. They developed an innovative solution. It’s a sonic distance warning device. It could be similar to the one that is included in cars while driving backwards,” adds Chagnaud. He calls it “an elegant design.

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