Bats navigate by bouncing their calls off every object that surrounds them, a behavior known as echolocation. But how do they keep things straight when several of these calls echo back at once? To find out, researchers trained big brown bats (Eptesicus fuscus) to fly through a dense maze of dangling plastic chains, then suddenly altered the maze path. Recordings from microphones placed on the bats' heads showed that the bats rapidly shifted the pitches of their calls up and down when navigating this new maze, allowing them to discriminate between multiple arriving echoes. It's as if the bats assign acoustic nametags to each call, the team reports online today in the Proceedings of the National Academy of Sciences. The findings might also apply to other animals who echolocate, such as whales and dolphins, further revealing how these animals' brains make sense of the noisy world around them.