Bat accelerator' unlocks new clues to how these animals navigate

"Bats are impressive navigators. Like so many mini submarines equipped with sonar, they deftly navigate dark forests and caves by listening for the echoes of their own calls. But how bats can tell which echo to follow while flitting around in a sea of overlapping and competing signals pinging off the myriad surfaces in their environments has been a mysteryuntil now."

"Imagine being at a party with hundreds or even thousands of people all talking at once; it's difficult to make out a single speaker, explains Marc Holderied, a professor of sensory biology at the University of Bristol in England and an author of the study. That's comparable to what a bat may be dealing with as the animal zooms around a dense foresta chaotic environment that can make it hard to echolocate."

"To solve this problem, the animals appear to rely on Doppler shift, or how a sound's pitch changes as a bat travels. As the bat is moving, Holderied says, this Doppler shift, in this complex echo of thousands of reflectors, carries information. Holderied and his colleagues observed wild pipistrelle bats using a contraption that they dubbed the bat accelerator. The machine is basically an eight-meter tunnel of treadmills covered in plastic leavesabout 8,000 of them all stapled on by hand,"

Many bat species navigate cluttered environments by interpreting echoes of their echolocation calls. Overlapping echoes from dense forests and caves create complex acoustic scenes that challenge echo identification. Bats use Doppler shifts generated by their own motion to distinguish which echoes result from their calls amid thousands of reflectors. Experiments with wild pipistrelle bats flying through an eight-meter treadmill tunnel covered in plastic leaves simulated a cluttered environment and showed that motion-induced pitch changes carry informative cues. Reliance on self-motion acoustics enables bats to select appropriate echoes for navigation and clarifies sensory processing in noisy, cluttered habitats.

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