THE dung beetle, with a brain the size of a grain of rice, is the first animal proven to navigate by the Milky Way.
South Africa has about 800 species of dung beetle, out of a global total of 6,000, says Marcus Byrne, a professor of zoology and entomology at Wits University.
About 10% of those 800 roll balls of dung — with the others simply burying themselves in it — and a few species out of those 80 do so at night.
In a paper written by Lund University’s Emily Baird, co-authored by Prof Byrne and published in online science journal Plos ONE, Prof Baird explains: "An interesting feature of dung beetle behaviour is that once they have formed a piece of dung into a ball, they roll it along a straight path away from the dung pile.
"This straight-line orientation ensures that the beetles depart along the most direct route, guaranteeing that they will not return to the intense competition (from other beetles) that occurs near the dung pile," the paper says. "Before rolling a new ball away from the dung pile, dung beetles perform a characteristic ‘dance’, in which they climb on top of the ball and rotate about their vertical axis."
"We think that (when they dance) they’re getting a celestial fix, and responding to navigational queues," Prof Byrne says.
This latest research, which will be published in Current Biology, shows the dung beetles use the Milky Way to keep in a straight line.
"Although their eyes are too weak to distinguish individual constellations, dung beetles 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 university says.
However, Prof Byrne notes there is a hierarchy of preference, in terms of celestial bodies, so if the moon is visible, dung beetles will use the stronger light source.
He also says the dung beetle is not singular in its use of the Milky Way as a navigational tool.
"There are absolutely other animals, but you can’t measure it," he says. "Dung beetles are such co-operative animals. You don’t have to train them or coax them. Give them poo and they behave."