Dung beetles navigate by the stars - research

Photo / Emily Baird

Oscar Wilde's famous quote "we are all in the gutter but some of us are looking at the stars" could not be more true of the humble dung beetle.

South African and Swedish scientists have discovered the insects use the Milky Way for orientation - the first time an animal has been proven to use our galaxy to navigate.

Although their eyes are too weak to distinguish individual constellations, the researchers found dung beetles use the gradient of light to dark created 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," said Professor Marcus Byrne from Wits University in Johannesburg.

The researchers' findings have been published in the journal Current Biology.

Previous studies from Byrne and his team had proved that dung beetles use the sun, the moon and polarised light for orientation. However the researchers were intrigued the critters were still able to maintain their straight courses even on clear moonless nights, so took their experiments into the Wits Planetarium.

Using a simulated night sky projected onto the planetarium dome, the researchers found the beetles performed best with a projected perfect starry sky, but were able to adequately orientate themselves with just the Milky Way.

Dr Marie Dacke of Lund University, Sweden, told BBC News it is the bar of light of the Milky Way rather than the individual points of light created by stars that is important.

"These beetles have compound eyes," Dr Dacke said. "It's known that crabs, which also have compound eyes, can see a few of the brightest stars in the sky. Maybe the beetles can do this as well, but we don't know that yet - it's something we're looking at.

"However, when we show them just the bright stars in the sky, they get lost. So it's not them that the beetles are using to orientate themselves."

The scientists suspect the beetles have a hierarchy of preference when it comes to available light sources - if the moon and the Milky Way are visible at the same time, the beetles probably use one rather than the other.

A few other animals have been proven to use stars for orientation, such as some birds and seals, but the dung beetle is the first animal proven to use the galaxy.