Dung Beetles Guided by the Milky Way, Avoiding Rivals

When dung beetles roll their large mounds of poo across the South African landscape, they like to look at the stars. In fact, a new study shows that dung beetles actually navigate using the Milky Way.

This new discovery, coming from a study published in Current Biology, shows that dung beetles are incredibly attuned to the sky. Moving in a straight line is crucial to the insects, which have to move as quickly as possible to avoid competition. When beetles come upon a large pile of poop, they craft the dung into balls and roll them as far away from the others as possible, often dragging along a female. The pair then buries the dung, which later becomes food for their offspring.

If the ball of dung is stolen by a rival, though, the dung beetle has to start all over again. Moving in a straight line, in other words, is part of the beetle's daily ritual of survival.

Although scientists already knew that dung beetles could move in a straight line away from dung piles by detecting a symmetrical pattern of polarized light that appears around the sun, they didn't know how the beetles moved at night. That's when Marie Dacke and her colleagues decided to study the beetles to find out.

They created a 10-foot-wide circular arena and then watched what nocturnal dung beetles did on moonless nights and cloudy nights. They fitted some of the insects with cardboard caps in order to block their view of the sky. After recording their results, they then took the arena into the Johannesburg Planetarium and ran the same experiment. The planetarium was programmed to show views of the night sky with the Milky Way.

"Dung beetles are known to use celestial compass cues such as the sun, the moon, and the pattern of polarized light formed around these light sources to roll their balls of dung along straight paths," Dacke said in a press release.

In the end, the researchers found that dung beetles rely on the Milky Way in order to travel in a straight line. This study has implications for other nocturnal bugs which may use similar methods to navigate.