The Beetles That Clean Up the World

The story

Here is a question you may never have thought to ask. All over the world, animals eat, and eat, and eat. Elephants, horses, sheep, deer, cows. And every animal that eats must also poo. Mountains of it, every single day. So why is the world not buried under it all?

Because the world has cleaning crews, and some of the busiest members are small, shiny, armoured beetles called dung beetles. To them, a fresh pile of dung is treasure. Some are rollers. They carve off a ball bigger than themselves, stand on their front legs, and push it away backwards with their back legs. Some are tunnellers, who dig straight down under the pile and pull the dung deep into the soil. Others simply move in and raise their babies right inside the pile.

And all that busy digging does the world a favour. Buried dung feeds the soil, the way compost feeds a garden. The beetles' tunnels let air and rain into the ground. And when the dung is cleared away fast, the flies that breed in it have far fewer places to lay their eggs.

Australia found out just how much dung beetles matter. Australia's own dung beetles had spent ages tidying up after kangaroos and wombats, which leave small, dry droppings. Then settlers brought cattle to Australia, and over time the herds grew into the millions. Cows leave big, wet pats, and the local beetles mostly could not break up and bury them. So the pats sat on the fields for months, and flies bred in them in enormous buzzing clouds that made life miserable. Scientists at Australia's national science agency, called CSIRO, had an idea: bring in dung beetles from lands where cattle have lived for ages. Over many years they released dozens of kinds, more than twenty settled in, and the beetles set to work burying the problem. The countryside got cleaner, and the clouds of flies shrank.

There is one more thing about dung beetles, and it may be the most astonishing of all. Some rollers work at night, and they push their ball in a straight line by looking UP. Scientists studying one night-rolling dung beetle found that it can steer by the glow of the Milky Way, the great river of stars across the sky. To test it, the scientists gently fitted some beetles with tiny cardboard caps that blocked their view of the sky. The capped beetles lost their way and wandered about, while beetles who could see the starry sky rolled their balls along beautifully straight paths. The scientists even brought beetles into a planetarium, a theatre with stars projected on the ceiling, and under the glow of the Milky Way alone, the beetles still rolled along lovely straight paths. A little cleaner of the ground, finding its way by the stars.

So the next time you see a beetle trundling along the ground, give it a nod. Some of its cousins are out there keeping whole grasslands clean, feeding the soil, beating the flies, and rolling their treasure home under the light of the Milky Way.