There very well could be danger to bats rising up from the ground across the world, and it has nothing to do with White-nose Syndrome or predators such as hawks, owls and snakes. Instead, it's buildings with metal and glass facades, according to research from biologists Stefan Greif and Sandor Zsebok.
The study published in Science says manmade structures like this act as a "sensory trap" to bats, which use echolocation to navigate their way through the air.
In a normal world, the bats send out the sound waves and the reflection of those sound waves let the bat know where the obstacles are so they can avoid them. Here's what those sound waves sound like when picked up on a bat detector:
However, the research from Greif and Zsebok indicates smooth vertical surfaces can wreak havoc on bats' ability to process the sound waves, because those surfaces cause the sound waves to reflect at steep angles.
"We found that bats can mistake smooth, vertical surfaces as clear flight paths, repeatedly colliding with them, likely as a result of their acoustic mirror properties," the biologists said.
For the study, they used 21 bats and set up a small flight room, with a glass mirror on one end. Then, they fired up the video camera and watched 19 bats slam into the mirror at least once. According to Greif, the bats that avoided the plate had sent out a signal when they were directly in front of it but with enough time left to quickly change course.
The researchers said none of the bats were injured in the study, thanks to the setup, which had the bats "in a narrow tunnel where they’re flying relatively slowly compared to the speeds at which they might fly outside."
The study isn't intended to sound the alarms but, instead, to be a starting point for the collection of data on bats because so little research has been done on bat collisions.
"Many bats are found injured, but people don’t keep track of what situations they find them," Greif said. "With millions upon millions of smooth vertical surfaces in our world today, such misperceptions could have considerable negative impacts on bat survival."
On the plus side, we know from this research as well as a previous study by Greif that smooth horizontal surfaces pose no issues for bats' echolocation.
They don't crash into it like the vertical surfaces, but interpret that as a source of water.
In those tests, when the "water" is really a mirror, they'll simply skim across it with their tongue.
h/t: Popular Science
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