“Little Beetle, Big Horns”
by Roberta Kwok
Science News for Kids [now Science News for Students], May 15, 2007
Kwok notes: I think I had interviewed Moczek once, and he agreed to let me visit his lab for beetle observations. This was the first time I had pitched Science News for Kids. In retrospect, I probably didn’t need so many scatalogical references; the editor noted in his assignment email that the story can’t contain any language a teacher would object to, so words like “crap” are out.
Dung beetles don’t get much respect. After all, they eat dung.
But dung beetles have a secret weapon: they can grow enormous horns. They use their horns to grab other beetles, throw them off trees, and flip them on the ground. “They beat the crap out of each other,” says Armin Moczek, a biologist at Indiana University at Bloomington.
No one knows how dung beetles first started growing horns. Moczek wants to find out.
He looks for beetles in pastures by picking up pieces of old dung. Underneath, he finds tunnels where the beetles are hiding. “You just need to get over the poop factor,” he says.
Recently, Moczek discovered that beetle horns aren’t just weapons. Baby dung beetles grow inside thick, hard shells called larval capsules. They use their tiny horns like can openers to poke themselves out of the capsule.
When some male beetles grow up, their horns disappear. These hornless males don’t have a chance against horned bullies.
So instead of fighting, they use “sneaking behavior.” A horned male will guard the entrance to a female’s tunnel, ready to fight intruders. The hornless male waits until the
guard isn’t paying attention. Then he runs into the tunnel, mates with the female, and runs out again before the guard notices.
Dung beetles have invented other clever tricks as well. They will do anything to get their favorite food: dung. In the South American rainforest, dung beetles grow a special claw that lets them hang onto a monkey’s fur as it leaps from tree to tree.
“Preferably on their butt,” says Moczek. “They wait for the monkeys to take a dump, and the moment they do, they drop with it. I’m not kidding.”