How dung beetles are guided by the Milky Way

Dung beetles invest quite a lot of time and energy shaping a nice round ball from a much larger pile of elephant dung. If they don’t get it safely away to their burrow, other dung beetles will fight them for it, rather than bothering to make their own.

If the beetle can’t navigate in a straight line, it’s quite likely to accidentally roll in a circle back to where it started from. Researchers from Lund University in Sweden have known for a while that dung beetles can use both the Sun and the Moon for navigation, but the puzzle was that they were still able to plot a straight line, even on a moonless night.

By testing beetles in a planetarium and selectively turning on and off different celestial light sources, they found that the beetles were using the strip of light from the Milky Way as their navigational cue.

There are still times of the year when the Milky Way lies too close to the horizon to be useful for navigation, but by combining it with their Moon compass, they minimise the number of nights where they are running blind.