Bats at risk from glass-clad buildings that deflect sonar

Glass-fronted homes and office buildings are harming bats because they cannot “see” them.

To navigate through the dark, bats rely on biological sonar, where they emit high-frequency sounds and use the returning echoes to detect obstacles. Yet injured and dead bats are increasingly found near buildings, leaving wildlife experts puzzled.

Now an experiment in Germany has shown that bats simply cannot “see” glass or mirrored buildings because shiny surfaces bounce the sound off in a different direction, so the creatures think there is nothing there. When scientists built a dark tunnel and installed a reflective metal plate at one end. They then released 21 greater mouse-eared bats, and found that 19 flew into the vertical plate at least once. The bats were unhurt.

Dr Stefan Greif, of the Max Planck Institute for Ornithology, in Pocking, said in the journal Science: “We now understand that smooth, vertical surfaces demonstrate a possible acoustic sensory trap for bats. [These] surfaces should be avoided at crucial sites such as migratory highways, key foraging habitats, or bat colonies.”

Ultrasonic deterrents in buildings would also help to keep the bats away.