Rattlesnakes, beware! The next time you spot a succulent-looking squirrel, it might actually be a cold-hearted robot. More specifically, it might be a “robosquirrel,” created by UC Davis professor of mechanical and aerospace engineering Sanjay Joshi. He built the robot squirrels as part of a study on rattlesnake behavior – a study which yielded some interesting results.

The rattlesnake is the main predator of the California ground squirrel – they particularly like to go after the pups. When an adult squirrel encounters a rattlesnake, they attempt to intimidate it by approaching it head-on, while elongating their bodies and flagging (flipping) and heating their tails. It appears to work, as the snakes will rarely attack a squirrel exhibiting such behavior.

Scientists, however, had never been certain exactly how big of a part was served by the heating of the tail – rattlesnakes are able to see in the infrared spectrum, so they could conceivably see the heat radiating from the tail. Because real squirrels always do both the flagging and the heating at the same time, however, it was impossible to tell.

The robosquirrels, made from mechanized stuffed squirrel carcasses, were designed to answer the question. Their tails can be made to move in a flagging motion while not being heated, or they can just be heated while standing still.

A robosquirrel approaches a rattlesnake in a tree (Photo: Rulon Clark, San Diego State University)

In order to test the robots, rattlesnakes were first located in the wild near San Jose, California. A track was subsequently laid down leading up to each snake, along with a video camera. The scientists then retreated to a blind, sent in the robot squirrel on the track, and watched what happened via the camera.

The snakes evidently believed the robosquirrels were the real thing, with one snake even biting one of the robots on the head. When the tails were heated but not moved, however, the snakes appeared to keep their distance. This suggested that the squirrels actually communicate with the snakes via tail heat – it’s reportedly the first time that infrared communication between animals has ever been documented.

This isn’t the first time, however, that robotic animals have been put to use in behavioral studies by UC Davis. Previously, robot anole lizards have been used to study display behavior, while a camera-equipped robot sage grouse hen was used to observe the birds’ mating behavior.

One of the robosquirrels can be seen in action (including receiving the head bite) in the video below.

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