How dung beetles use stars to find their way home

Swedish researchers find that the bugs can use the heavens to correctly orient themselves

They may have bad taste in sustenance, but dung beetles sure are resourceful at night.
(Image credit: Martin Harvey/CORBIS)

Long before GPS and radio, seafarers relied on the stars to guide them to their destinations. In the animal kingdom, birds and seals have demonstrated a similar capacity for celestial navigation. And now there's one more living creature we can add to the list: The humble dung beetle.

Yes, the feces-eating bug joins more exalted company thanks to new research from Lund University in Sweden. In order to feed themselves and their offspring, male beetles seek out fresh piles of guano, roll some of it into a ball, and quickly push it home with their hindlegs before a competitor can snatch their prize away.

In a previous experiment, neuroethologist Marie Dacke was astonished when she observed beetles seemingly finding their way home at night without any other visual cues readily available save for starlight. Indeed, the path they took home was not just accurate — it was virtually a straight line.

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To test if the bugs were using the stars to guide them, Dacke and her colleagues set up a meticulous outdoor experiment. They constructed high-walled arenas to remove all the beetles' visual cues except for the night sky. After leaving piles of dung and sending the beetles out to scavenge, the team discovered that the bugs could correctly orient themselves and push their balls home without any trees, plants, or other terrestrial landmarks. (Repeated experiments indicated the bugs didn't need the moon, either.)

Researchers, in this case, think they're able to accomplish this thanks to special photoreceptors in their eyes. While beetles lack the visual acuity to pick out individual stars, they can see blobs of blurry star patterns, which function as a "good enough" reference point to set their internal compass in the right direction.

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