Dung Beetles Navigate Using Milky Way
Dung beetles have long been known to use the light of the sun and moon to guide them in straight lines. Earlier this year, Swedish scientists have discovered that the beetles can also use the starry sky for orientation.
Collecting dung balls is a competitive business, and dung beetles must travel as fast as they can away from the source in order to avoid fights. To avoid circling back to the source, they use astrological cues to guide them in straight paths.
The scientists have found that on clouded nights, the beetles wandered without direction. However, on clear moonless nights, the beetles are able to travel in straight lines, leading to the hypothesis that stars are used as directional cues.
In order to test their theory, a field test was conducted whereby the dung beetles were placed in a circular arena surrounded by meter high black cloth. The cloth prevented view of landmarks, but allowed a view of the moonless sky. Cardboard masks were placed on the beetles, which blocked the view of the sky.
The test compared how long it took for a masked beetle and an unmasked beetle to reach the edge of the arena from the center. Unmasked beetles, which had an unobstructed view of the stars reached the edge 3 times faster then masked beetles. The test was repeated in a planetarium with similar results.
The compound eyes of the beetle aren’t sensitive enough to sense individual stars and constellations. Instead, they detect the arching glow of the milky way for orientation.
Picture: Arno Meintjes Wildlife on Flickr