Scientists Discover First Mammal to Navigate with Polarized Light: Mouse-Eared Bat

Scientists have discovered the first mammal that uses polarized light to navigate, and it happens to be a bat. It turns out that the greater mouse-eared bat uses polarization patterns in the sky in order to find its way.

Polarized light is essentially the way the sun's light is scattered in the atmosphere. Polarization patterns, therefore, depend on where the sun is in the sky. They're clearest in a strip across the sky about 90 degrees from the position of the sun at sunset or sunrise. Yet what's interesting is that animals can see these patterns long after sunset. This means they can orient themselves even when they can't see in the sun, including when it's cloudy.

"We know that other animals use polarization patterns in the sky, and we have at least some idea how they do it: bees have specially-adapted photoreceptors in their eyes, and birds, fish, amphibians and reptiles all have cone cell structures in their eyes which may help them to detect polarization," said Richard Holland, co-author of the new study, in a news release.

While bats use echolocation to navigate, this echolocation only works up to about 50 meters. This means that the mammals must have some other method to get around. That's why scientists studied 70 adult, female mouse-eared bats. They showed the bats one of two different types of polarization patterns at sunset.

So what did they find? It turns out that the bats that had been shown a shifted polarization of light headed off in a direction shifted at right angles from the controls released at the same time. This seemed to show that the bats could indeed detect polarized light.

That said, the researchers still aren't sure how the bats detect the light. But the fact that they can detect it in the first place may help scientists conserve this species. Currently, bat populations are declining due to white-nose syndrome and wind farms. But learning how they navigate, researchers can put protections in place that can help these mammals.

The findings are published in the journal Nature Communications.