Here's how window panes pose threat to bats

Bats are well known for their echolocation - sending out sound waves and listening for their echo - to navigate through areas riddled with obstacles, but a study has recently revealed that this useful ability is hindered by smooth vertical surfaces like metal or glass windows on buildings.

According to researchers, several observations of bats colliding with smooth vertical surfaces (such as glass windows) suggest that bats have problems recognising them.

Of 21 individual bats, 19 collided with the vertical plate at least once (on average 23 percent of passes) but never with the horizontal plate.

The results clearly explained as to why injured or dead bats are often found near buildings, and underscore the negative impact of human development on wildlife.

To navigate through the dark, bats rely heavily on echolocation, where they emit high-frequency sounds and use the returning echoes to detect, classify, and localise objects in their environment.

Study author Stefan Greif, along with his colleagues, monitored greater mouse-eared bats (Myotis myotis) as they flew through a continuous, rectangular flight tunnel in the dark.

In the corner of the dark tunnel, they placed a metal plate either vertically or horizontally.

In natural habitats, smooth vertical surfaces are rare, yet bats encounter smooth horizontal surfaces in the form of water.

The researchers found that when the bats collided with the vertical plate, they were producing fewer calls, spending less time in front of the plate, approaching the plate at a more acute angle, and had higher flight speeds relative to the bats that avoided collision.

The authors report similar findings in field experiments outside of caves of three different bat species.

The results appear in Journal of Science.