By reputation bats are “blind” and most people are aware that they use echolocation, or sonar, to find prey. A bat’s navigation system, however, would put many modern jet aircraft to shame. Bats use a combination of sight, smell, the Earth’s magnetic field, echolocation, the position of the stars and, according to a recent study, polarized light to find their way around.

Polarization patterns develop depending on where the sun is in the sky. They are best viewed at an angle 90° from the position of the sun at sunrise or sunset. Animals that use polarization, however, can detect these patterns long after the sun is down. Some dung beetles have even been shown to use the polarization of the moon for navigation.

Various species of birds, reptiles, amphibians and insects are known to use polarization for navigation. When it comes to bats, researchers have shown that they use the sun to set their internal compass, though they’re still not sure how they accomplish it.

‘We know that other animals use polarisation 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. But we don’t know which structure these bats might be using,” said Dr. Richard Holland of Queen’s University Belfast and co-author of the study in a statement.

A bat can travel hundreds of miles from their home every evening to go hunting, but by dawn they will always return to the same location.

“Most people are familiar with bats using echolocation to get around. But that only works up to about 50 meters, so we knew they had to be using another of their senses for longer range navigation,” said Stefan Greif of Queen’s University Belfast, lead author of the study.

Previous studies have suggested that bats, the first mammals known to use polarization, might detect polarization patterns when they emerge from their sleeping locations at dusk. The researchers used this theory to conduct their research.

Holland, Greif and colleagues from Tel Aviv University showed two different types of polarization patterns to 70 adult, female mouse-eared bats at sunset and then took the animals to one of two release sites in Bulgaria. Both sites were 12 to 15 miles from their home roosting site.

All of the animals were released, with small radio transmitters attached to their backs, at 1 am when no polarization light was visible. The bats who had been shown a shifted polarization pattern took off at right angles to their counterparts in the control group.

Researchers are attempting to understand bat navigation, in part, to help protect the species. Bats, are natural pest controllers. A single adult bat can eat up to 8,000 mosquito sized insects per night. More bats means a decreased need for insecticides and improved public health. In Europe alone, wind turbines are killing an estimated 300,000 bats annually. This could translate to an additional 500 billion flying insects per year.

‘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 … Anything we can do to understand how they get about, how they move and navigate will be step forward in helping to protect them,” said Holland.

This research can be found in full in the journal Nature Communications.