The Rattle Is a Deterring Signal That Works Best with Sympatric Species

The rattlesnake rattle is one of the most iconic communication signals in nature, yet its evolutionary function remains poorly understood. To test the long-standing hypothesis that rattling acts as a deterrent, we developed a 3D-printed robotic rattlesnake capable of displaying the multimodal sensory stimulus produced by a rattlesnake. This robot was presented to 38 species of zoo-housed animals in a series of behavioral trials. Animals displayed aversive response to the rattling signal, suggesting that the rattle functions as a deimatic signal by triggering reflexive avoidance response. Sympatric species exhibited even stronger fear response to rattling, suggesting an evolved, innate fear to the signal. These results offer insights into how complex antipredator signals can originate and diversify in the animal kingdom.