When a squirrel encounters a rattlesnake in the wild, it does something very peculiar to survive its brush with the predator. That something is so peculiar, in fact, that we've had to build robot squirrels just to try to understand it.
Biologists at UC Davis have enlisted the help of engineers to build these robo-squirrels, which you can see in the photo up top. The hope is that the use of these robosquirrels can reveal just what exactly squirrels are trying to accomplish when they encounter a rattlesnake — other than simply survive, of course.
A live squirrel will do two things when it sees a rattlesnake. One action is to start moving its tail in a flagging motion. The other is to actually heat up the temperature of its tail. Because rattlesnakes can see in the infrared wavelengths, they should be able to see both the tail move and it heat up. The question is which of these two signals is important — or whether it's somehow a combination of these two — and just what message it's supposed to send to the rattlesnake.
The problem is that researchers can't get a squirrel to only flag its tail, or heat it up. To that end, the engineers at UC Davis have built these robosquirrels, which allow the biologists to simulate the two squirrel behaviors one a time. All the research so far suggests it's the heated tail, not the flagging motion, that the snake responds to. That makes it one of the first known examples of infrared communication, especially between two distinct species.
Actually, it might be more accurate to call it infrared miscommunication - the whole point of the signalling seems to be to help throw off the rattlesnake enough that the squirrels can dodge the eventual strike. The UC Davis research has also pointed to the apparent strategic thinking going on in the rattlesnakes' heads — while it's obviously not really possible to say for sure, their observations do suggest the rattlesnakes are using some rather complex decision-making to figure out how best to deal with the squirrels. In some cases, it seems the rattlesnakes just decide it's best to cut their losses after dealing with these confusing critters, as sometimes the snakes just leave the area completely after encountering these flagging, tail-heating squirrels.
Via UC Davis. Image by Andy Fell, UC Davis.