26 Jan 2013

African dung beetle can navigate by the stars

6:04 am on 26 January 2013

Like sailors of old and Saharan nomads, it turns out the African dung beetle can navigate by the stars. It's the first insect known to be able to do this.

A study by Marie Dacke of Lund University, Sweden, is reported in the journal Current Biology.

A BBC science reporter says it shows the insects will use the Milky Way to orientate themselves as they roll balls of muck along the ground.

"The dung beetles are not necessarily rolling with the Milky Way or 90 degrees to it; they can go at any angle to this band of light in the sky. They use it as a reference," Dr Dacke told BBC News.

Dung beetles like to run in straight lines. When they find a pile of droppings, they shape a small ball and start pushing it away to a safe distance where they can eat it, usually underground.

Getting a good bearing is important because unless the insect rolls a direct course, it risks turning back towards the dung pile where another beetle could get its ball.

Dr Dacke had previously shown that dung beetles were able to keep a straight line by taking cues from the Sun, the Moon, and even the pattern of polarised light formed around these light sources.

She took the insects (Scarabaeus satyrus) into a planetarium in Johannesburg, South Africa, where she could control the type of star fields a beetle might see overhead.

The beetles were put in a container with blackened walls to be sure the animals were not using information from landmarks on the horizon.

The BBC reports the beetles performed best when confronted with a perfect starry sky projected on to the planetarium dome, but coped just as well when shown only a diffuse bar of light that is the plane of our Milky Way Galaxy.

"These beetles have compound eyes," she told the BBC. "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."