African dung beetles have eyes too weak to distinguish individual constellations but can use the gradient of light to dark provided by the Milky Way to ensure they keep rolling their dung balls in a straight line and avoid circling back to competitors at the dung pile, Swedish and South African scientists report in the journal Current Biology.
While birds and humans navigate by the stars, the discovery is the first convincing evidence for such abilities in insects, the researchers say.
"Even on clear, moonless nights, many dung beetles still manage to orientate along straight paths," Marie Dacke of Lund University in Sweden said. "This led us to suspect that the beetles exploit the starry sky for orientation -- a feat that had, to our knowledge, never before been demonstrated in an insect."
The beetles can transport their dung balls along straight paths under a starlit sky but lose the ability under overcast conditions, the researchers said.
On starry nights the beetles climb on top of their dung balls to perform a "dance" during which they locate light sources to use for orientation, they said.
"The dung beetles don't care which direction they're going in; they just need to get away from the bun fight at the poo pile," Marcus Byrne of the University of the Witwatersrand in South Africa said.