Certain surfaces foil bat echolocation
Bat echolocation is a finely tuned sense. By emitting high-frequency calls and listening for returning echoes, bats can deftly navigate complex surroundings and precisely target moving prey in the dark. But this extraordinary capability is not foolproof. A study published Thursday in Science reveals a weak spot in bat echolocation: smooth, vertical surfaces such as the metal or glass plates on buildings can trick a bat into thinking it is flying in open air.
The findings might help explain why the creatures are often found dead or injured near buildings and other smooth structures, said Stefan Greif, an author of the study and a postdoctoral researcher affiliated with the Max Planck Institute for Ornithology in Germany and Tel Aviv University in Israel.
When a bat approaches a smooth, vertical surface from an angle — as it would when turning a corner in a rectangular tunnel — its echo-locating calls mostly reflect away from it. It’s not until a bat gets very close to a flat, vertical surface that some of its calls end up hitting the plate at a 90-degree angle and bouncing right back.
At this point, Greif and his collaborators noted, bats tended to change their echolocation patterns, shortening the time between calls, to collect more information. But it was often too late — out of 78 instances they observed of bats coming close to a vertical plate, 25 resulted in near misses while 53 resulted in crashes.
Echolocation does not prevent bats from flying into smooth, vertical surfaces. Above, a greater mouse-eared bat.