[Animals] How Rattlesnakes Deceive Humans About Where Exactly They Are

[FNX Magokiler]

The warning of the rattlesnake, that famous chi-chi-chi, is one of the noises in nature that makes our hair stand on end, because when you hear it, you are already too close.

But, according to a new study, published August 19 in the journal Current Biology, that warning is more complex than we thought.

By analyzing the warning vibrations of the western diamondback rattlesnake (Crotalus atrox), scientists found that the snakes shake their rattles at low frequencies of up to 40 hertz, or slower, when the threat is far away. But when the intruder gets too close to its comfort zone, a distance that varies depending on the specimen, the rattle suddenly changes to a higher speed, emitting a warning at a higher frequency of between 60 and 100 hertz.

When people in the study were asked how far away the rattle was in a virtual reality meadow, their answers were fairly accurate when the rattle was slower, or at a lower frequency. However, when the rattle accelerated, humans were fooled into thinking that the snakes were much closer than they really were.

When a rattlesnake shakes its tail slowly, the human ear perceives each rattle well. But at a higher frequency, the individual sounds merge into a continuous song, which sounds "completely different to our human ear," says Boris Chagnaud, a neuroscientist at the University of Graz in Austria and lead author of the study.

 

 

What's more, due to a perceptual quirk, rattling at high frequencies sounds louder to us even though it is basically at the same wave amplitude, or volume, Chagnaud says.

"Maybe that's another function of the rattlesnake, trying to confuse predators," says Bree Putman, a herpetologist at California State University in the United States, who was not involved in the study.

The secret language of bells
Rattlesnakes are native to America and there are more than 35 different species that live between southern Canada and Argentina. When threats are seen, the snake shakes the tip of its tail like a natural rattle, rattling interlocking sections of cupped keratin, the same protein that makes up nails and hair.

While humans are now beginning to investigate the intricacies of rattlesnake language, other species have been listening to the rattles of these snakes for much longer.

For example, squirrels use the frequency of a rattle's rattle to know how dangerous the snake is.

This works because snakes are cold-blooded or ectotherms. "Their performance depends on how hot they are," Putman explains; "Thus, a hotter snake is more dangerous and rings its bell faster."

 

https://www.nationalgeographic.es/animales/2021/08/como-enganan-las-serpientes-de-cascabel-a-los-humanos-sobre-donde-estan-exactamente