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Dung beetles use stars to navigate - study

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By John Yeld

Cape Town - So what’s a dung beetle’s favourite celestial object? Why, Uranus, of course.

But that’s not quite as crude a joke as it may sound, because a Wits University scientist and his research partners have just published their discovery that these fascinating little creatures can navigate using stars (Uranus is a planet, of course) or, more correctly, groups of stars, as they undertake their Sisyphean task of transporting balls of dung.

The experiments show that despite their tiny brains and minimal computing power, the beetles can use the relatively dim light of the Milky Way (dim compared to the sun and moon) for orientation – the first species proven to have this ability.

“They therefore have the potential to teach humans how to solve complex visual processing problems,” says Wits University’s Professor Marcus Byrne, who works on the “Visual Orientation in Dung-breeding Scarabs” project with colleagues from Pretoria University and Lund University in Sweden.

Byrne, who teaches zoology and entomology, explains that although dung beetles’ eyes are too weak to distinguish individual constellations, they use the gradient of light to dark provided by the Milky Way to ensure they keep rolling their balls in a straight line and don’t circle back to competitors at the dung pile.

“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,” he says.

In earlier experiments, he and his team fitted beetles with “caps” that blocked light from reaching their eyes while proving that these specialised creatures use the sun, moon and polarised light for orientation.

They also discovered that the beetles climb on top of their dung balls to perform an orientation “dance” during which they locate light sources to use for orientation.

Now, their latest experiments, conducted under the simulated night sky of the Wits Planetarium, have shown that the beetles are also able to use the “mohawk” shape of the Milky Way to navigate.

Byrne says he and his research partners have a great time working with the fascinating little creatures which “present some light relief in their single-minded approach to life and its challenges”. - Cape Argus

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