Bats are apparently the only mammal with the ability to use polarized light in order to set their internal compasses. The news comes from a study of the animal’s navigational habits that was published in Nature Communications online today.The research solves the mystery of the bat’s uncanny ability to navigate, despite the short range efficacy of the echolocation systems that the animals use to get around caves and other environments.

Bats internal compass

According to the authors of the study, which included researchers from the University of Belfast, Northern Ireland, and the University of Tel Aviv, Israel, “We had already demonstrated that bats used a magnetic compass that was calibrated by cues observed at sunset. The question was, what cues? It was known that birds calibrate the magnetic field with the pattern of polarization at sunset, so we tried the same for bats.”

Bats use light to set compass

The experiment that proved the use of polarized lights by bats was relatively simple. The researchers had two groups of bats, one that was allowed to view the polarization of light in the night sky without obstruction, and a second that viewed the phenomenon shifted at 90 degrees. The second group, when it came time to release them, the bats who had been exposed to the shifted light flew off at 90 degrees to the control group.

The experiment shows that the bats do indeed use polarized light in order to navigate, but it gave no clue as to how the animals are able to detect the phenomenon. According to well known research certain insects have eyes that are specially adapted to see the polarized light. Bats may indeed be able to detect it with their eyes, but additional research will have to be carried out in order to prove or unfound that supposition.

The principle scientists behind the research included Richard Holland and Stefan Greif, of Queen’s University Belfast, with Ivailo Borissov and Yossi Yovel of the University of Tel Aviv, and the research concentrated on the abilities of the female reater mouse-eared bats, demonstrating their ability to recalibrate an internal magnetic compass using the night sky’s polarized light.

Polarized light is a property of waves that allows their oscillation in more than one orientation. This means that a light wave is able to travel in distinct patterns that are apparently visible, or at least detectable, by the bats.

Complicated navigation builds a world for bats

The realization that polarized light plays an important role in the navigational systems of bats builds out an increasingly complicated view of the way in which the animals work. The animals are known to use echolocation in order to get around small areas, a talent that is about as opaque to humans as any alien sense imaginable. Today’s research confirms their use of polarized light, and other research supports the idea that the bats have an internal magnetic compass.

According to Richard Holland, “We know that bats can use echolocation and vision for navigation when they are in a familiar place or can see familiar cues. But outside this range the ‘map and compass’ mechanism comes into play, where the animal determines its position and then takes up the compass direction it needs to head in to reach its goal.”