Why Dung Beetles Dance on Poop: They’re Mapping the Sky
Understanding how bugs navigate could help build better robots.
Image: Basil el Jundi/Lund University
Out on the African savannah, where dung beetles live, every piece of poop is like a "treasure" packed with nutrients that must be protected at all costs, biologist Basil el Jundi, of Lund University in Sweden, told me.
The beetles "have to ensure that others aren't going to steal it," so they form a piece of poop into a ball and roll it as quickly as possible away from the dung pile, el Jundi said. But, before doing so, they stop for a moment and dance on top of the ball.
It seems like a funny thing to do, when you're in a hurry. Researchers never really understood why dung beetles would stop and do this dance, but now they have an idea.
In a new paper in Current Biology, el Jundi and co-authors from Sweden and South Africa suggest that dung beetles, who are known to navigate by the light of the Milky Way, are taking a "snapshot" of the sky when they dance—a mental note of cosmic bodies like the sun and stars, that will help them roll their ball in a straight line, and get away from others who might want a piece of their dung as quickly as possible.
The dung beetle dance, el Jundi told Motherboard, involves climbing atop a ball of poop and "rotating around their own body axis, most often by 360 degrees." After doing a little spin, they climb down and start rolling.
In the study, the team put some dung beetles in an indoor arena in South Africa, with an artificial sky full of fake stars above them. They could regulate the amount of light coming from these artificial stars, and where they were positioned in the sky, to watch how the beetles reacted. Insects can read all sorts of cues that are invisible to humans, el Jundi said, like the polarization of light, which helps them find their way even when there's no sun.
By comparing their mental "snapshot" to their changing environment as they rolled the ball of poop, these beetles managed to go in a straight direction.
It's the first time that dung beetles have been shown to take mental "snapshots" of the sky, according to el Jundi. Ants are also known to make a mental map of their surroundings—but they focus on the ground. Other bugs, like bees and wasps, will take little tours of their nests, but scientists haven't figured out why they do so.
Studying how insects navigate is important, said el Jundi, who wrote this paper with some of the same scientists who made the discovery that dung beetles can navigate by the light of the Milky Way. "What we do is basic science," he continued, but it will have other applications down the road—for example, for engineers who are trying to build autonomous vehicles and robots, and ensure that they go in a straight line.
"That's not our aim," he said, "but it's what people may use our results for."
And it's just further evidence of how amazing these little dung beetles are. They make a living off poop, and they're guided by the stars. It doesn't really get more poetic.
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