A study revealed that rattlesnakes can change the frequency of their rattle the closer humans get to them. The findings were published on Thursday in Current Biology. Rattlesnakes are known to prey on smaller animals like rodents and rattle their tails when they feel threatened.

Boris Chagnaud, the lead author of the study, said that he noticed rattlesnakes changed their rattling to a higher frequency when he went closer to them and the frequency was lowered when he stepped away.

Chagnaud, who is a professor in the department of biology at the University of Graz in Austria, said that the incident was similar to a car backing up. The “acoustical signals warning you how close an object is behind you” beeps faster the closer you are to an object, Chagnaud stated.

When approached, the snakes increase their frequency from about 40 Hertz to 60-100 Hertz, CNN reported, quoting the study.

To confirm this pattern, he designed a virtual reality environment where virtual snakes reacted the same way.

“The subjects underestimated the distance to the virtual snake whenever it jumped to the higher frequency range,” Chagnaud said.

This meant that the higher the frequency, the more people will believe that the snake was closer (like a defense mechanism). “It’s more likely that a large mammal might stop and not step on the usually well-camouflaged snakes,” Chagnaud said.

“Like other snakes, rattlesnakes, of which there are numerous species in North America, are more interested in being undetected than confronting any other animal other than their prey,” he said.

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Even though rattlesnakes can protect themselves with venom, a researcher said that snakes often try and avoid using it whenever they can. He also said that future studies may focus on how they use their rattles to attract prey. He said this could be possibly be done through “auditory mimicry of species that serve as prey to other species.”