In the study, African dung beetles (S. satyrus) wore "caps" to block their view of the sky. Image courtesy of Marie Dacke et al.
They may spend their lives rolling around on balls of poop, but dung beetles have their eyes on the stars. A new study shows that these simple bugs actually depend on the Milky Way to find their way around.
Christopher Columbus traveled by following the stars, as did Harriet Tubman. There are even birds and seals that use celestial navigation, but in the insect world, this finding is a first. In fact, the dung beetle is the first animal known to navigate via the subtle glow of the galaxy as a whole, rather than by individual stars. This may be because its compound eyes give the dung beetle a wide-angle view but poor image resolution.
To make this discovery, researchers put dung beetles to the test inside a planetarium. They found that the bugs traveled in a (relatively) straight line with or without a moon, and no matter how many stars were visible, as long as the sky was clear. But when it clouded over (or, in the case of the study, when the researchers covered the the beetles' eyes with a tiny cap) those straight lines became a mess of overlapping loops.
The paths of the dung beetles when the stars were (A) visible and (B) obscured by the beetles' caps. Image courtesy of Marie Dacke et al.
The researchers deduced that it was the vague white line of the Milky Way that the beetles looked to for direction. The results were published Thursday in Current Biology.
In addition to being a more efficient way to travel, moving in a straight line is essential for dung beetles to distance themselves from the mêlée of the dung pile as quickly as possible, thus reducing the chances of their turd ball being snagged by another greedy beetle. Now that would be unfortunate.
