Forget the phrase “blind as a bat.” New experiments suggest that members of one species of these furry flyers—Myotis myotis, the greater mouse-eared bat—can do something no other mammal is known to do: They detect and use polarized light to calibrate their long-distance navigation. Previous research hinted that these bats reset their magnetic compass each night based on cues visible at sunset, but the particular cue or cues hadn’t been identified. In the new study, researchers placed bats in boxes in which the polarization of light could be controlled and shifted. After letting the bats experience sundown at a site near their typical roost, the team waited until after midnight (when polarized light was no longer visible in the sky), transported the animals to two sites between 20 and 25 kilometers from the roost, strapped radio tracking devices to them, and then released them. In general, bats whose polarization wasn’t shifted took off for home in the proper direction. But those that had seen polarization shifted 90° at sunset headed off in directions that, on average, pointed 90° away from the true bearing of home, the researchers report online today in Nature Communications. It’s not clear how the bats discern the polarized light, but it may be related to the type or alignment of light-detecting pigments in their retinas, the team suggests. The bats may have evolved to reset their navigation system using polarized light because that cue persists long after sunset and is available even when skies are cloudy. Besides these bats (and it’s not known whether other species of bat can do this, too), researchers have found that certain insects, birds, reptiles, and amphibians can navigate using polarized light.