Sailors don't need to read the stars anymore—they've got GPS. But dung beetles do not have GPS. And it now appears that they use the Milky Way as a compass.

Dung beetles need a keen sense of direction so they can roll their dung patties away from the communal dung pile, and feast in peace. Ten years ago, Marie Dacke at Lund University in Sweden and her colleagues discovered that some dung beetles use polarized moonlight to keep a straight course. But what’s their plan on moonless nights?

Dacke tracked the beetles as they successfully rolled dung away from the center of a circular sandbox. Then she blocked the beetles' starry view with tiny cardboard hats, and set 'em loose again. Without stars to guide them, the beetles traveling twisted, circular paths. Those findings appear in the journal Current Biology. [Marie Dacke et al., Dung Beetles Use the Milky Way for Orientation]

The beetles' tiny compound eyes probably aren't sharp enough to make out individual stars. In a planetarium, for example, when only 18 bright stars were illuminated, the beetles got lost. But the faint streak of the Milky Way seems to be just enough light to point them to a dung dining hole—no reservations required.

—Christopher Intagliata

[The above text is a transcript of this podcast.]

Also see Dung Beetles Follow the Stars