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Weird Animal Question of the Week

Dung Beetles Roll With It

How do starry-eyed dung beetles get around during the day?

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On a roll! Dung beetles use cues from the sky to roll their dung balls in a straight line away from the dung hill. 


As much as we love GPS, everyone has a story of digital directions gone wrong. Comedian Ross Noble once told a story about driving across Australia’s Nullarbor Plain with the directions: "Drive forward for two days. Then turn left." But in the end, the road was so long that without further prompting, he missed the turn.

If only we had a dung beetle's knack for navigation.

In 2013, National Geographic reported on a study in the journal Current Biology showing that African dung beetles were able to navigate using the Milky Way to orient themselves, the only animal species known to show this ability. (See video: African Dung Beetle)

The beetle's star trek prompted commenter jtbean in Rhode Island to ask our Weird Animal Question of the Week: "How do dung beetles navigate in Alaska in summer when the sky is never dark and the Milky Way can't be seen?"

Sunny Outlook

Eric Warrant, a biologist at the University of Lund, Sweden, and co-author of the study, said via email that there are indeed dung beetles at such latitudes, but they are a different species than the ones that roll balls of dung, which are the only ones likely to steer by the stars. If the ball-rolling beetles did live that far north, Warrant says, they would probably be active during the day and would use other cues, such as the pattern of celestial polarized light.

Celestial polarized light produces a fixed, compass-like pattern in the sky, not visible to us but evident to the beetles and other insects. It comes from the "scattering of light in the atmosphere around the sun or the moon," Warrant says. There is also a pattern around the moon at night by which nocturnal beetles can navigate, though it's a million times dimmer.

What might the polarization patterns look like if we could see what the beetles can? Diagrams of the phenomenon show concentric circles, broken up like dashes and ringing the planet.

Light-headed

The patterns of polarized light might be invisible to us, but they are used by many other creatures. "Insects are particularly well-adapted to use this signal," says Katy Prudic, an entomologist at Oregon State University. "They use it to navigate and for sexual signaling, to attract mates." A 2003 study published in the journal Nature showed that polarized light reflecting off the iridescent wings of Heliconius butterflies is a signal that attracts males to females.

And dung beetles, she says, are peculiar in that they shun landmarks used by other insects to find their way. Moths, for example, will orient themselves to the moon at night but will use the physical landscape to navigate by day. Beetles, however, won't take a left at the red barn or the tree stump—they're focused on the sky.

A study co-authored by Warrant in 2012 says that beetles will lose their straight-line navigation abilities under overcast conditions or if they can’t see the sky, yet their steering isn't affected by altering landmarks.

But nevermind the impracticality of that intense focus. Take it from the beetles: Just because you're surrounded by dung doesn't mean you can't have your head in the stars.

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