"Even on clear, moonless nights, many dung beetles still manage to orientate along straight paths," Marie Dacke, a biologist at Sweden's Lund University, said in a news release. "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."
That's an amazing claim. But what's just as amazing are the lengths to which the researchers went to make their case.
First, they built a 10-foot-wide (3-meter-wide) circular arena in a South African game reserve and watched what troops of nocturnal dung beetles did on moonlit nights, moonless nights and cloudy nights. They fitted the bugs with little cardboard caps to block their view of the sky. They even fitted some of the bugs with transparent plastic caps, just to make sure that any differences they saw were due to the sky blockage rather than the presence of the caps.
Then the scientists took their dung-beetle arena into the Johannesburg Planetarium and ran the same experiment, to eliminate the possibility that the beetles were using terrestrial landmarks to plot their course in the dark. The planetarium was programmed to show the night sky with the Milky Way, or the Milky Way without the brightest stars in the sky, or the brightest stars without the Milky Way, or just the diffuse glow of the Milky Way with no stars at all.
The bottom line was clear: Those bugs could keep track of how the fuzzy streak of the Milky Way was oriented in the sky, to make sure they rolled their balls of dung in a suitably straight line.
Why is that so important? Without the proper orientation, the beetles might circle back to the dung pile, where they'd have to face all the other beetles trying to steal away their tiny balls of poop. That would put the bugs' intended meal at risk. "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 South Africa's University of the Witwatersrand explained in a news release.