Tuesday, February 17, 2009

You horny devil, you


Let me share with you this charming illustration from a recent issue of Nature (February 12). Four dung beetles of the same species. At the upper right, the female. At upper left, the alpha male, with an outsized horn. Below him, the beta male. And to his right, below the female, the hornless gamma male. Yes, three levels of macho. You can surely guess which one the female prefers. And which poor fellow must rely on more subtle strategies of seduction. Isn't nature grand?

And this for a creature who pitches his mansion in "the place of excrement."

Dung beetles were venerated as gods by the ancient Egyptians. And in this day when recycling is all the rage -- indeed, a moral imperative -- dung beetles should be venerated again as recyclers par excellence. Without them we would be up to our...

Never mind. Let J. Henri Fabre, the famous turn-of-the-century French entomologist, have the say. He spent years studying the lives of these "dealers in ordure," as he called them. He filled cages with the insects, and bribed local children with lollipops to bring him heaps of excrement gathered from the fields and roads. And he watched. Watched as the dung beetles cut the excrement into balls, rolled them away, and buried them.

The dung-balls serve as food for adult beetles and for larvae. "Out of filth, she creates the flowers," rhapsodized Fabre, "from a little manure, she extracts the thrice-blessed grain of wheat."

The curious ball-rolling habits of these insects evolved tens of millions of years ago. Several entomologists have suggested that hordes of dung beetles followed dinosaurs around, cleaning up behind. It makes perfect evolutionary sense. The mountainous droppings of the lumbering dinosaurs were rich in nutrients -- an ecological resource not to be wasted. A triceratops plop must have seemed like manna from heaven to the earliest dung-scavenging insects.

Today, thousands of species of dung beetles clean up after large animals worldwide. They inhabit pastures, paddocks, roadsides and prairies-anyplace animals graze. They come in all sizes, from ant-sized beetles that roll pea-sized balls, to beetles bigger than a baby's hand that cut spheres the size of baseballs from elephant dung.

Both males and females harvest ordure. Like Cinderella and her Prince Charming, a pair is likely to meet at the ball. Together, they cut and roll -- the female sometimes rides the ball while the male pushes it along with his back legs. When they find a suitable place, the male buries the ball by digging the earth from underneath, and the female sinks along with their treasure. Underground, the pair feeds upon the ball, then mate. It is a quaint nuptial rite, one of nature's more charming courtships, a fecal fairy tale.

Much has been learned about these insects since Fabre huddled over his cages. Dung beetles clean up messes that would choke out plant life upon which the mess-making animals depend. They fertilize and aerate the soil. They remove breeding sites for disease organisms and flies.

And with what athletic skill! Entomologists Bernd Heinrich and George Bartholomew watched African dung beetles roll balls at rates as fast as 40 feet per minute. Ball stealing is another activity studied by the entomologists. Apparently, some beetles would rather commandeer a ready-made ball than fashion one of their own. The ensuing battles for possession contain more grappling and body tosses than a World Wrestling Federation Royal Rumble. A big horn may help.

It is inspiring to think of all those generations of entomologists, down on their knees, clothespins on their noses, studying the habits of the ball-rolling beetles. These day, scientists get government grants to go where the elephant plops abound -- the cost of research has gone up since Fabre distributed lollipops. As Fabre had it, "Notwithstanding their disgusting occupation, dung beetles are of a very respectable standing."