A new study found bats still need light to fly at night; a finding that contradicts earlier beliefs stating these nocturnal creatures use only echolocation to navigate their environment.
"Most people are familiar with bats using echolocation to get around. But that only works up to about 50 metres, so we knew they had to be using another of their senses for longer range navigation," said Stefan Greif, lead researcher and biologist from the Max Planck Institute for Ornithology in Stanberg, Germany, in a news release.
Grief and his colleagues from Queen's University Belfast observed 70 adult, female greater mouse-eared bats for the study. The research team discovered the European bat species also used polarization patterns to fly, making it the first mammal to employ such light waves for navigation.
Polarized light waves are individual, illuminated streams that align parallel to one another and fluctuate on a 90-degree angle during sunrise and sunset. Earlier studies claimed migratory birds and monarch butterflies used it as a compass.
"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 polarisation," said co-author of the study Dr. Richard Holland of Queen's University Belfast.
The researchers divided the bats into two groups: the first flew during sunset while the other was released at 1:00 a.m., where no polarization was present. The bats were released in Bulgaria, about 20 to 25 kilometers from their home. The team attached radio transmitters to the bats to track their flight directions.
The study showed the bats that were exposed on polarization light waves flew in the same direction, while the other group dispersed in various directions. But even if the researchers were able to prove bats also depend on polarized light for their nighttime navigation, they admitted further study is needed to point out how they are able to do so.
Further details of the study were published in the July 22 issue of Nature Communications.
