The rattlesnake’s rumble is the most terrifying sound you hear during a hike. What is the reason the rattlesnakes create this famous sound?

“Everything tells us that they rattle to alert predators,” David Pfennig, Professor of biological sciences at the University of North Carolina at Chapel Hill, explained to Live Science. Rattlesnakes can appear scary animals, but they’re not at the highest point in the food chain. If a predator or creature that might crush it, such as bison or a coyote or a bison, for instance, comes close, the rattle will warn the predator to keep away; otherwise, it could get fangs.

However, scientists have yet to learn this. According to Pfennig, up to the 1950s, there was much disagreement about what the rattle was being used to do. Many believed it was used to attract friends.

The rattle functions as an aposematic sign which means that instead of being silent or hidden, the animal exhibits a characteristic that can make it stand out from its prey. There, but many species use the aposematic signal. The poison dart frogs are vividly colored, for instance, and black and yellow stripes distinguish bees. However, being conspicuous and threatening is only effective in the presence of a legitimate threat. The dart frog’s vibrant colors are a mighty potent poison, and behind the stripes of the bee are stingers. Amida’s set of venomous fangs is amid a rattlesnake’s rumble. Predators who recognize the signals of danger can live for another day.

In 2016, Bradley Allf Bradley Allf, an undergraduate student in the lab of Professor Pfennig and his coworkers, looked into the development of rattlesnakes’ rattle. They discovered that the snakes’ ancestors likely rattled their tails when they were threatened long before the appearance of rattles on rattlesnakes.

All examined the tail-shaking behaviors of 56 species of snakes and discovered that even though rattlesnakes were by far the only snakes studied to possess rattles, most snakes included in the study quickly flick their tails when they feel threatened. In addition, snakes tightly related to rattlesnakes tend to shake their seats more quickly and frequently than those more distantly related to rattlesnakes. When rattles developed, and snakes could use them, they already knew how to use them.

“Usually when snakes or other reptiles shed, they get rid of their old skin and replace it with new skin from underneath,” Boris Chagnaud, a professor at the Faculty of Natural Sciences at the University of Graz in Austria, explained to Live Science. “It’s the same for the rattlesnakes, except that at the tail end, one piece of skin remains attached, which means that every time they shed, they get one more keratinous segment on the rattle, which is the part that generates the sound.” (Keratin is a type of protein also present in hair, our nails, and the skin.)

The loosely connected segment of dead skin is hollowed and stuffed with air. Instead of rattling pieces of keratin in the rattle, like a maraca, the parts snap together to make the famous rattling sound. The rattling process is far more sophisticated than it appears.

In 2021, Chagnaud joined an experiment team that found that rattlesnakes create an auditory illusion using the rattles they make. They discovered rattlesnakes start to rattle their tails at low frequency — at the very least, at first. However, if the prey – or in their study, an individual human attempting to approach an imaginary snake started to move towards the snake, then the rattlesnake’s roar would get more and more rapid.

It’s similar to the sound alarms in the “car that beeps faster as you approach a wall,” Chagnaud explained.

If a predator keeps moving towards the snake, its rattling rate will increase suddenly by 20-30 hertz, giving the impression of the snake being far away from where it is.

If an animal can’t even hear its own rattle, the rattlesnakes certainly make good use of this sound.