Dung beetle is one of nature’s most surprisingly sophisticated navigators. On a clear night in the African bush, a dung beetle rolls its ball of dung in a perfectly straight line away from the dung pile, never circling back, never veering. For a long time nobody knew how it managed this. The beetle is small, its eyes are simple, and it is navigating across featureless ground in the dark.
The answer, confirmed in 2013 by Marie Dacke at Lund University and her colleagues, is that dung beetles use the Milky Way as a compass. They are the first animals demonstrated to navigate by the galaxy rather than by individual stars. On moonless nights, when the Milky Way is the brightest feature in the sky, beetles fitted with tiny cardboard caps that blocked their view of the sky lost their straight-line orientation immediately. Remove the cap, and they corrected course.
The straight line matters because dung is a contested resource. Other beetles will steal a ball if given the chance, so the beetle that rolls its ball directly away from the pile, as fast as possible, in a straight line, gets the most distance between itself and the competition in the shortest time. The navigation is not about finding a destination. It is about escaping a starting point as efficiently as possible.
Dung beetles are ecologically important in ways that are easy to underestimate. They bury dung, which aerates soil, cycles nutrients, reduces parasite loads in livestock, and suppresses fly populations that breed in surface dung. Studies in South Africa have estimated the economic value of dung beetle services to the cattle industry at hundreds of millions of dollars annually. An animal that navigates by the Milky Way is also doing the unglamorous work of keeping pastures functional.
The Dung Beetle’s Ball: Food, Shade, and Water
The dung ball is not just food. It is also a thermoregulation tool. On hot days, dung beetles climb on top of their balls to get their feet off the hot ground, using the cooler surface of the ball as a temporary refuge. They have also been observed wetting their faces with fluid from the ball to cool down through evaporation. The ball they are rolling to eat is also their shade and their water source on a hot African day.
Male dung beetles that produce larger balls attract more females, because ball size signals the male’s ability to provide food resources. Females assess ball size before deciding whether to accompany a male, and in some species the female rides on top of the ball while the male rolls it — which is either romantic or practical depending on your perspective.
The Diversity of Dung Beetles
There are over 6,000 species of dung beetle worldwide, found on every continent except Antarctica, feeding on the dung of a remarkable range of animals. Some species are highly specialized, feeding only on the dung of specific host species. Others are generalists. The diversity of the group reflects millions of years of coevolution with the mammals whose dung they process, and the decline of large mammal populations in many parts of the world has been accompanied by declines in the dung beetle communities that depended on them.
How the Milky Way Compass Works
What makes the dung beetle’s celestial navigation especially remarkable is that it does not require identifying individual stars. The beetle detects the broad luminous band of the Milky Way as a whole — essentially using the galaxy’s light gradient as a fixed reference line across the sky. This is a fundamentally different strategy from the star-compass navigation documented in birds and seals, which rely on star patterns or the rotation of specific constellations around the celestial pole.
Researchers tested the beetles in a custom-built planetarium in Johannesburg, projecting the full starry sky, the Milky Way alone, or a starless sky in turn. Beetles under the full sky and Milky Way-only conditions both navigated effectively. Under a starless sky they lost their direction. The conclusion was clear: the diffuse band of galactic light was sufficient for orientation, even without identifiable star points. You can read more about the original research at Lund University.
Three Lifestyles, One Family
Not all dung beetles roll balls. The family Scarabaeidae is divided into three broad functional groups based on how they handle dung. Rollers are the ones that form a ball and push it away from the source. Tunnellers dig directly beneath the dung pile and bury it underground without moving it far. Dwellers simply live and breed within the dung pile itself. Each strategy has its own competitive advantages and ecological consequences, and different environments tend to favour different groups.
The tunnellers are arguably the most important for soil health. By burying dung directly, they move large quantities of organic material and nutrients into the subsoil rapidly, improving water infiltration and reducing surface evaporation. In heavily grazed grasslands, the presence of active dung beetle communities has been shown to measurably reduce the need for synthetic fertilisers. For more on the natural world’s unlikely ecological heroes, visit the Wild Wonders Daily Blog.