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Dung Beetles Use the Sky to Navigate – but How Exactly?


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First time I read this I really thought this was a load of crap.  😃



The Milky Way shows the way

But the moon isn’t out every night. What then? Another potential cue came to Byrne and colleagues one night in 2007.

“After a great day’s work, the moon goes down, and we’re sitting and having a beer under the beautiful desert sky of the Kalahari, and there’s the Milky Way,” Byrne recalls. “And one of us said that, if we can see that, they must be able to see that.”

And they do. Although the insects’ eyes are too small and weak to navigate from single stars, a 2013 study revealed that they apparently see the brighter, wide band of light that the Milky Way draws across the night sky. In experiments with the dung beetle Scarabaeus satyrus under the simulated night sky of the Johannesburg planetarium, Dacke, Byrne, Warrant and colleagues found that the Milky Way’s path could steer the insects’ course — making dung beetles the first known animals capable of orienting themselves using this cue.

This presented a puzzler, however, since the researchers had earlier observed that the insects meandered on moonless nights. But when the worried scientists reviewed their notes, they found that these earlier experiments took place in months when the Milky Way was too low in the night sky for the beetles to see it.

By the sky only

One set of cues that dung beetles don’t rely on for navigation are landmarks or anything else on the ground. “We’ve created arenas with high walls and a 30-centimeter opening, and we thought, ‘OK, guys, solve this one, there’s only one way to get away from the dung pat’ — and they fully ignored it,” Dacke says.

In another study, the scientists filled half the arena with dung beetles tied to the floor. One might imagine that beetles rolling their dung balls would steer clear of their tethered brethren — “but no, they just rolled over the tied-down beetles,” Dacke says.

The scientists conducted still other experiments in which dung beetles wore broad-brimmed cardboard caps so they could not see the sky. The haberdashery caused the beetles to roll around in circles, “fully lost,” Dacke says — confirming their dependence on celestial cues. Since they don’t have permanent nests, instead regularly moving from one ephemeral dung pat to another, memorizing landscapes may not prove useful when they spend their life wandering about, says neuroethologist Emily Baird of Stockholm University.

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