Dung Beetle Rejects Directions, Says It Will Follow the Milky Way

A dung beetle on the open grassland has turned down an offer of directions from a local ant, explaining that it already knows exactly where it is going and that the route has been agreed with the galaxy. The beetle, who was rolling a ball of dung roughly the size of a grape, was approached shortly after dark. The ant suggested a shortcut round a tuft of grass. The beetle declined politely, without letting go of the ball.

The beetle has become well known in the area for its unusual style. Rather than pushing the ball forwards like a sensible animal, it stands on its front legs and pushes backwards with its back legs, facing away from where it is going. Every so often it stops, climbs on top of the ball and turns slowly on the spot, in what witnesses describe as a small, very serious dance. Then it climbs down and carries on in exactly the same direction as before.

Asked about the dance, the beetle said it was checking its bearings, and that it would be happy to explain if anybody else was going in a straight line. The ant, who had been going in several directions at once, said this seemed like a lot of fuss. A grasshopper nearby added that she had once followed a beetle for twenty minutes to see where it was going, and had simply ended up further away.

The beetle's determination is explained by a crowded neighbourhood. A fresh pile of dung attracts beetles from every direction, and the most common danger is not a predator but another beetle trying to steal a finished ball. The fastest way to escape, the beetle points out, is to roll away in a straight line, because any wobbly, curving route risks bringing you straight back into the crowd.

On cloudy nights, the beetle admits, things are harder. It has been seen wandering in circles, bumping into stones and, on one occasion, arriving back at the original pile with its ball and an air of great embarrassment. It has asked that this not be reported. It has been reported.

Remarkably, the heart of this is true. Researchers working with dung beetles in southern Africa found that the beetles really do roll their balls away in straight lines at night, and that on moonless nights they can use the Milky Way to do it. In a series of experiments, including some carried out under the artificial sky of a planetarium, the beetles stayed on course when they could see the band of the Milky Way and lost their way when it was hidden.

The dance is real too. When a dung beetle climbs on its ball and turns, it appears to be taking a snapshot of the sky to set its heading. In one experiment, researchers fitted beetles with tiny cardboard caps that blocked their view of the sky, and the beetles wandered aimlessly. Scientists believe the beetles do not use individual stars, but the overall glow of the Milky Way. So the next time you look up at that pale stripe across a dark sky, remember that somewhere, someone very small is using it to get home with dinner.