Polarized Light Gives New Meaning to 'Blind as a Bat'

The phrase "blind as a bat" may no longer be an accurate statement for those with eye issues. A recent study published in the journal Nature Communications found that bats look for polarized patterns of light so that they can properly navigate through the sky.

"We had already demonstrated that bats used a magnetic compass that was calibrated by cues observed at sunset," said Richard Holland of Queen's University Belfast, in a news release. "The question was, what cues? It was known that birds calibrate the magnetic field with the pattern of polarization at sunset, so we tried the same for bats."

As a huge number of species--including bees, fish and even dung beetle's--this form of navigation, the findings reveal that bats are the first mammals to do so.

However, researchers still remain a bit uncertain as to how bats accomplish their travels this way.

Furthermore, this discovery adds to a list of other systems used by bats to travel through the night, including echolocation, the Earth's magnetic field and even certain smells.

For their research, scientists were able to show 70 adult, female mouse-eared bats one of two different types of polarization patterns at sunset. All of them were released in Bulgaria around 12-15 miles from their home roost during a morning when polarization was not visible.

For bats that did see a shifted pattern of polarized light, they flew off in a direction at right angles from those that weren't shown a shifted pattern.

Dr. Richard Holland of Queen's University and co-author of the report added that the bat population had taken a serious hit, partly due to wind turbines that had harmed or killed the animals.

"We know that bats must be 'seeing' the turbines, but it seems that the air pressure patterns around working turbines give the bats what's akin to the bends," Holland concluded, via the Press Association. "It's most common in migratory species, with around 300,000 bats affected every year in Europe alone. You just find bats dead at the bottom of these turbines. One option is to reduce turbine activity during times of peak migration."

Another issue that is taking the lives of many bats is White-Nose syndrome (WNS), in which a fungus grows around the muzzle and wings of hibernating bats. For those infected with the bacterium, there is a 90 percent mortality rate.

Due to the disease's severity, the U.S. Fish and Wildlife Services has called a moratorium on caving activities in affected areas. Many hope that this can prevent the risk of more infections and deaths over time.