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The researchers developed a theory: Perhaps the snakes’ sudden, high-frequency clicks created an illusion of proximity that served as a warning. Dr. Chagnaud wanted to test this theory on buffalo at Munich Zoo, before realizing that it would be much easier to use university students, who are often more willing test subjects.

Volunteers sat in a chair in the middle of a room wearing a virtual reality headset that moved them toward a snake hidden in a grassland at dusk. As the frequency of the rattles increased, the volunteers pressed a button to indicate that they thought they were about a meter away from the snake. All subjects pressed the button when the clicker jumped in frequency, misinterpreting their true distance.

The researchers suggest that this sudden jump in frequency is an evolved behavior that rattlesnakes use to trick the listener as to their true distance from the snake. “The change in the rattle is a trick of the snake,” said Bruce Young, an anatomist at the Kirksville College of Osteopathic Medicine in Missouri, who reviewed the paper.

However, Dr. Chagnaud explained that the search for this trick is only a hypothesis. According to another explanation, a quick click may be a strategy to get the listener’s attention, similar to eliciting a startle response in the same way that loud noise causes a person to startle. However, Dr. Chagnaud points out that a snake can produce a startle response more efficiently by jumping from 3 hertz to 100 hertz; He believes the slow oscillating ramp up to 100 hertz can be better explained by an illusion of proximity.

But since snakes have been in North America for at least six million years, humans have never been the intended evolutionary target of the rattlesnake. Dr. Rowe said this article doesn’t necessarily shed light on how animals that co-evolved with rattlesnakes, such as badgers or canids, perceived the rattle.

Unfortunately, doing the same virtual reality experiment on a mustelid would probably be chaotic and stressful. “Can you put little glasses on a badger?” Dr. Rowe wondered aloud. “Badgers are very stubborn.” In his eyes, California ground squirrels would be a much better virtual reality rattlesnake foe.

Dr. “There are a lot of brilliant young scientists who could find a way to sit a squirrel on a monitor with tiny earplugs,” Rowe said.