Bats are slamming into modern building that have large expanses of glass or mirrored surfaces, according to researchers, who are calling for better monitoring of these risks, especially in areas with large bat populations.
The winged mammals have the ability to fly at top speeds in the dark, instinctively avoiding natural obstacles such as trees. But smooth, vertical surfaces like glass windows are a “blind spot” for bats, a study says, making them “potentially dangerous” for bats.
Stefan Greif of the Max Planck Institute for Ornithology near Munich in Germany, lead author on the study, says, “Bats predominately rely on their echolocation system to forage, orientate, and navigate.” He explains,
We found that bats can mistake smooth, vertical surfaces as clear fight paths, repeatedly colliding with them, likely as a result of their acoustic mirror properties.
Bats use echolocation to find hazards when they fly, in order for them to roost and forage for food, the BBC reports. They make calls and listen to returning echoes to build a sonic map of their location, using it to navigate. But vertical mirroring surfaces appear to trick the animals into thinking their path is clear. In addition, bats treat smooth, horizontal surfaces like water, and attempt to drink from them.
Researchers analyzed the flight behavior of greater mouse-eared bats in dark flight tunnels. They placed a metal plate vertically or horizontally in the corner of the tunnel to see what would happen.
Of the 21 bats, 19 bumped into the vertical plate at least once, but never with the horizontal plate. They were producing fewer calls and flying at the vertical plate at a more acute angle, and at faster speeds. The same was found of three wild bat species. No bats were injured in the experiment.
These findings could explain why many dead or injured bats are found near buildings, the researchers say, although there is a need to gather more evidence for the threat to be fully realized.
The study was published in Science.