Dung beetles navigate using Milky Way
The ancient Egyptians associated the dung beetle with the sun, seeing a parallel between the way it rolls its ball of dung and the way the sun moves across the sky.
And now there's another celestial association for the creatures, with the discovery that, along with the sun and the moon, dung beetles orient themselves by the light of the Milky Way.
Although their eyes are too weak to distinguish individual constellations, say researchers, dung beetles use the gradient from light to dark provided by the Milky Way to ensure they keep rolling their balls in a straight line and don't circle back to competitors at the dung pile.
"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," says Professor Marcus Byrne from Wits University.
The team had first shown that dung beetles use the sun, the moon and polarised light for orientation, by giving the beetles 'caps' which blocked light from reaching their eyes. They also discovered that the beetles climb on top of their dung balls to perform a 'dance' during which they locate light sources to use for orientation.
Now, further experiments, conducted under the simulated night sky of the Wits Planetarium, have shown that the beetles also use the Milky Way to orient themselves.
"We were sitting out in Vryburg, conducting experiments, and the Milky Way was this massive light source. We thought they have to be able to use this - they just have to!" said Byrne.
The scientists suspect the beetles do have preferences when it comes to available light sources, meaning that they probably only use the relatively weak light from the Milky Way when there's nothing better available.
A few other animals have been proven to use stars for orientation, but the dung beetle is the first shown to use the galaxy.