Ground squirrels are pretty awesome — not only are they disarmingly cute, but they have also evolved numerous defenses to avoid being eaten by rattlesnakes, including actively attacking the snakes, developing resistance to rattlesnake venom, and even using their tails to send infrared warning signals that scare the snakes away. This study describes another amazing squirrel behavior: using rattlesnake perfume to hide from predators. Prior to this study, it was known that squirrels would chew on old rattlesnake skins and then lick their fur to coat themselves with the snakey odor. What was not known, however, was whether the effect was to scare away snakes, as opposed to scaring away other squirrels or acting as a flea repellent. It turns out that squirrels wearing rattlesnake perfume are less attractive to the snakes, indicating that the scent has a specific anti-predator purpose. This is one of the first known examples of an animal applying a predator’s scent as a disguise, but we guess it won’t be the last.
“Ground squirrels (Spermophilus spp.) have evolved a battery of defences against the rattlesnakes (Crotalus spp.) that have preyed on them for millions of years. The distinctive behavioural reactions by these squirrels to rattlesnakes have recently been shown to include self-application of rattlesnake scent-squirrels apply scent by vigorously licking their fur after chewing on shed rattlesnake skins. Here, we present evidence that this behaviour is a novel antipredator defence founded on exploitation of a foreign scent. We tested three functional hypotheses for snake scent application–antipredator, conspecific deterrence and ectoparasite defence–by examining reactions to rattlesnake scent by rattlesnakes, ground squirrels and ectoparasites (fleas). Rattlesnakes were more attracted to ground squirrel scent than to ground squirrel scent mixed with rattlesnake scent or rattlesnake scent alone. However, ground squirrel behaviour and flea host choice were not affected by rattlesnake scent. Thus, ground squirrels can reduce the risk of rattlesnake predation by applying rattlesnake scent to their bodies, potentially as a form of olfactory camouflage. Opportunistic exploitation of heterospecific scents may be widespread; many species self-apply foreign odours, but few such cases have been demonstrated to serve in antipredator defence.”