Human beings have long navigated by the stars. A new study shows that at least one member of the animal kingdom, the dung beetle, does so as well—using the Milky Way, as it turns out.
Some background: True to their name, dung beetles dine on other animals’ excrement. The males collect it by digging it out of a dung heap, fashioning that into a little ball that weighs up to 50 times more than they do, and rolling it away, according to National Geographic. It’s also not uncommon for them to collect a female along the way.
That’s where the Milky Way comes in. Not for romantic stargazing, but for a quick getaway, according to a study published this week by a research team from the University of Lund in Sweden headed up by biologist Eric Warrant. For self-preservation, this inches-long insect (it fits neatly across the palm of a researcher’s hand) must hightail it quickly from the dung heap lest its competitive counterparts nab the goods and make the beetle start all over again. Given that the shortest distance between two points is a straight line, it’s essential for the beetle to take this most direct route away from those who would steal its food.
Lots depends on the beetle’s astronomical acuity. The ball-rolling male and his mate bury the dung as food for their future offspring.
The mystery had already been stripped from the question of how the dung beetle manages a straight line during the day, National Geographic reported. Photoreceptors in their eyes allow them to detect polarized light that emanates in a symmetrical pattern from around the sun. But once the sun goes down, how do they do it? Warrant and his colleagues think they have found the answer.
Observing the dung beetle Scarabaeus satyrus in South Africa, the researchers conducted several experiments both outside and in a planetarium. After trying several variations of moonlight, “it occurred to us that maybe they were using the stars—and it turned out they were,” Warrant told National Geographic. This would explain why the beetles are able to navigate even when there is no moon. Further testing, which included the deployment of little star-blocking hats over the beetles’ eyes, revealed that the straight line guiding them was the streak of light that is our very own galaxy.