Squirrels aren't squirreling out of their ongoing battle with snakes, but they may be turning tail. California ground squirrels are able to intimidate rattlesnakes, researchers have found, by heating their tails 3 degrees; the rattlers perceive infrared waves, and back off. Even more surprising, the squirrels are savvy enough not to bother with the heat show for gopher snakes, which don't have the thermal sensors.
Adult squirrels have developed immunity to rattlesnake venom, the Sacramento Bee reports, but the babies—or squirrel pups—are vulnerable. Hence the heat wave, along with other aggressive behavior from adults—mostly moms—when rattlers come around. A second study found that the rattlers recoiled more from robotic squirrels when the fake animals heated up, regardless of other aggressive signals.