Waste makes haste for dung beetles, indispensable specialists in recycling

January 19, 1992|By New York Times News Service H

In the vast world of beetles, they have the stamp of nobility, their heads a diadem of horny spikes, their bodies sheathed in glittering mail of bronze or emerald or cobalt-blue.

The ancient Egyptians so worshiped the creatures that when a pharaoh died, his heart was carved out and replaced with a stone rendering of the sacred beetle.

But perhaps the most majestic thing about the group of insects known romantically as scarabs and more descriptively as dung beetles is what they are willing and even delighted to do for a living.

Dung beetles venture where many beasts refuse to tread, descending on the waste matter of their fellow animals and swiftly burying it underground, where it then serves as a rich and leisurely meal for themselves or their offspring.

Each day, dung beetles living in the cattle ranches of Texas, the savannas of Africa, the deserts of India, the meadows of the Himalayas, the dense undergrowth of the Amazon -- any place where dirt and dung come together -- assiduously clear away billions of tons of droppings, the great bulk of which comes from mammals such as cows, horses, elephants, monkeys and humans.

Scientists have long appreciated dung beetles as nature's indispensable recyclers, without which the planet would be beyond the help of even the most generous Superfund cleanup project.

But only recently have they begun to understand the intricacies of the dung beetle community and the ferocious inter-beetle competition that erupts each time a mammal deposits its droppings on the ground.

Researchers are learning that every dung pat is a complex microcosm, a teeming habitat not unlike a patch of wetland or the decaying trunk of an old redwood, although in this case the habitat is thankfully short-lived.

For scarabs, it may be said that waste makes haste, and entomologists have discovered that as many as 120 different species of dung beetles and tens of thousands of representatives of those species will converge on a single large pat of dung as soon as it is laid, whisking it away within a matter of hours or even minutes.

"If it weren't for dung beetles," said Dr. Bruce E. Gill, a scarab researcher at Agriculture Canada, a government agency in Ottawa, "we'd be up to our eyeballs in you-know-what."

The diversity of beetles that will flock to a lone meadow muffin far exceeds what ecologists would have predicted was likely or even possible, and scientists are being forced to rethink a few pet notions about how animals compete for limited goods and what makes for success or failure in an unstable profession like waste management.

They are learning that beetles have evolved a wide assortment of strategies to get as much dung as possible as quickly as possible, to sculpt it and manipulate it for the good of themselves and their offspring, and to keep others from snatching away their valuable booty.

Researchers are also realizing that chance and good fortune play a far greater role than they had thought in determining who reaches a prized resource first and who is able to make the most of it.

The knowledge they are gleaning about the dung beetle community also applies to their understanding of how species compete for more conventional resources, including plants or prey animals.

"I'm fascinated by the enormous diversity of dung beetles that you can see in one dung pat," said Dr. Ilkka Hanski of the University of Helsinki in Finland. "I don't know of any other insect community where such large numbers could be seen in such a small area. It is extraordinary."

Many findings have been gathered into a new book, "Dung Beetle Ecology," edited by Dr. Hanski and Dr. Yves Cambefort and published by Princeton University Press.

The book is intermittently technical and arcane, but it nevertheless manages to accomplish the seemingly impossible task of transforming a beetle that one previously might have preferred not to dwell on at all into an insect of such worthiness, respectability and even charm that one would like to immediately order a few hundred thousand to help clean up the streets of one's home town.

Dung beetles, it turns out, are among humanity's greatest benefactors. Not only do they remove dung from sight, smell and inadvertent footstep, but by burying whatever they do not immediately eat they add fertilizing nitrogen to the soil.

"Experiments have shown that by burying the dung underground, the beetle increases the amount of nitrogen getting from the dung and into the soil, as opposed to being lost in the atmosphere," Dr. Gill said.

Like earthworms, the beetles churn up and aerate the ground, making it more suitable for plant life. Dung beetle larvae consume parasitic worms and maggots that live in dung, thus helping to cut back on micro-organisms that spread disease.

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