Light polarization helps bats navigate

Los Angeles Times : Although bats rely largely on echolocation for finding their way around, it only works over relatively short distances. For longer flights, bats have been known to use other cues, such as visible light and Earth’s magnetic field. Now researchers have found that bats also use polarized light—sunlight that has been scattered and refracted as it passes through Earth’s atmosphere yet is invisible to humans. To test that theory, Stefan Greif of the Sensory Ecology Group at the Max Planck Institute for Ornithology and colleagues put adult female greater mouse-eared bats in special boxes with windows. By covering the windows with filters, they were able to manipulate the sky’s natural polarization patterns. They found that the bats that experienced the light manipulation flew off in directions 90 degrees to those of the control group. The researchers have determined that polarization does not give direction but rather helps the bats calibrate their internal magnetic compass. Finding out how the bats perceive polarized light is the scientists’ next task.