The rattle of a rattlesnake turns out to be way more complicated than we knew. Researchers have discovered that the snakes are masters of auditory deception, reports the BBC. In a new study in Current Biology, researchers found that they rattle their tails at a frequency of 40 hertz if a potential predator is detected at, say, a distance of 6 feet. But the snakes ramp it up to between 60 and 100 hertz if the threat gets closer, per National Geographic. At this rate, the noise is "completely different to our human ear," says lead researcher Boris Chagnaud of the University of Graz in Australia. For instance, the rattle seems to be louder, even though it technically is not. The upshot is that to human ears, the snakes sound much closer than they actually are, an outcome that might benefit snake and human alike.
"Snakes do not just rattle to advertise their presence, but they evolved an innovative solution: a sonic distance warning device similar to the one included in cars while driving backwards,” says Chagnaud in a news release. He offers an example to Live Science: "Imagine you walk towards the snake, (and) it starts to rattle slowly, increasing the rattle events incrementally." Within 6 feet, if the snake changes the frequency to make it sound as if you're practically on top of it, "then it fooled you," he writes. One theory is that the snakes developed the technique eons ago to avoid being stepped on, perhaps by bison. It's possible the rattlesnakes also use the method to confuse non-human predators to escape an attack. Far from being a rudimentary acoustic warning, the rattle "is in fact a far more intricate interspecies communication signal,” says the research team. (Read more rattlesnake stories.)