The dung beetle as celestial navigator
Only humans, birds, and seals are known to navigate using stars. But the dung beetle does use the Milky Way to chart its path, say scientists.
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From the experiments, "we thought that they could be using the stars [for orientation], but dung beetles have such small eyes that they don't have the resolution, or sensitivity, to see individual stars," Dacke said.Skip to next paragraph
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So the researchers moved their setup into a planetarium to tease out the information the beetles were extracting from the starry sky. They repeated the experiment under several different conditions, such as showing only the brightest stars, showing only the diffuse band of the Milky Way and showing the complete starry sky. The beetles took about the same amount of time to cross the arena when only the Milky Way was visible as when they could see a full star-filled sky. And they were slower to cross under all other conditions.
Previous experiments showed another dung beetle, S. zambesianus, is unable to roll along straight tracks on moonless nights when Earth's galaxy, the Milky Way, lies below the horizon, Dacke noted. Taken together, these results suggest dung beetles navigate using the gradient of light provided by the Milky Way. However, this technique would only work for beetles living in regions where the Milky Wayis distinct. "What they are doing in the Northern Hemisphere [of Earth], I don't know," she said.
The researchers are now trying to determine the relative importance of the different sky cues dung beetles use. "If they have the moon, polarized light and the Milky Way, will they use all cues equally?" Dacke said.
The research is published online (Jan. 24) in the journal Current Biology.
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