New research shows dung beetles use the stars and the Milky Way to help them keep a straight course.
Dung is a valuable food for the dung beetle, and when it finds fresh faeces it collects and rolls a ball home to eat without fear of other beetles stealing it. It’s important for the dung beetle to be able to stay on course – without a reference point, it could end up accidentally rolling its dung back to the dung pile!
The beetles push their ball with their hind legs, allowing the upward pair of eyes (they have two pairs) to take in light from the sky. Previous research had shown that dung beetles could navigate by the sun and the moon, but had also found the beetle Scarabaeus satyrus could keep a straight course on moonless nights. To find out how they were using the night sky, researchers put S. satyrus in an arena and gave some tiny hats (because who says science can’t be cute?).
Beetles wearing tiny hats were just as poor at rolling in a straight line as those rolling in overcast conditions. But dung beetles have such small eyes – what exactly were they seeing? By simulating the night sky in the Johannesburg planetarium, the team found that beetles were using the stripe of the Milky Way to guide them home. Beetles in the only-Milky-Way condition crossed the arena in the same amount of time as those in the star-filled-sky condition. But when exposed to only the brightest stars (and no Milky Way), the beetles got lost.
“This is the first time where we see animals using the Milky Way for orientation,” said lead researcher Marie Dacke (Lund University, Sweden). “It’s also the first time we see that insects can use the stars.” She believes this ability will be found in many other animals, commenting, “I think night-flying moths and night-flying locusts could benefit from using a star compass similar to the one that the dung beetles are using.”
Photo credit: Marcus Byrne.