Army ants, croaking frogs may tell story of vanishing jungle life

Long after most civilized souls have gone to bed in these parts, you can find Lee Harper on his hands and knees trying to woo a three-yard-long column of Amazon army ants into a 20-gallon plastic trash bucket.

Wilson Spironelo spends the eight hours of his workday shoveling up dirt from the forest floor.

Barbara Zimmerman, for her part, is best known hereabouts for padding about the jungle and pointing a microphone at the muck to record frog calls.

Left to themselves, each one of these young researchers would probably emerge from the woods several months from now with the makings of a weighty tome destined for the annals of some esoteric scientific journal.

But together this trio, plus about 35 colleagues and forest hands from the United States, Canada, South America, and Europe, represent what has been called the largest and perhaps the most ambitious scientific experiment ever conducted in a tropical rain forest.

Their turf is nearly 60 square miles of the central Amazon in northern Brazil.

And their research could be a scientific key to understanding what appears to be a grim future for the jungle.

''If you fly over Brazil or most anywhere in the world, what you see is that the forest is being divided up into smaller and smaller patches,'' says Richard O. Bierregaard, a young Ivy League-trained ornithologist, who started this massive in vivo jungle experiment with a bit of seed money five years ago.

''This is the trend worldwide,'' he says. ''Now obviously most of these areas are not going to be protected wilderness reserves. What we have to do is prepare for that fact.''

Working under the auspices of the Washington-based World Wildlife Fund and the Brazilian National Institute for Amazon Research, Bierregard and his team of researchers - ranging from university undergraduates to PhDs - work in five deep-forest camps located a punishing three-hour jeep ride from this Amazon port city. A musty ranch-style house in residential Manaus fitted with an Apple II computer and dozens of makeshift wood file boxes doubles as project headquarters and a bungalow for mud-caked workers on liberty. Mr. Bierregaard coordinates it all.

Today, Bierregaard can say with some confidence that the project, inspired by Amazon bird researcher and World Wildlife Fund vice-president Thomas Lovejoy, may begin to answer riddles about the world's most complicated ecosystem. ''This is the first time we will have concrete data about how to maintain species of plants and animals in the forest,'' says Paulo Nogueira Neto, Brazil's special secretary of the environment, who will soon issue orders protecting the experimental reserve.

''This is of enormous ecological interest to Brazil and to the world,'' he says.

Titled originally ''Minimal critical size of ecosystems,'' the project was inspired by a debate that has roiled conservation science for the better part of a decade: How small can a wilderness area be before animal and plant species begin to die off or disappear?

''There are a couple of ways to go about resolving this debate,'' Mr. Bierregaard says. ''You can walk around for a few years, noting down everything you see, if you have the time. Or, you can isolate parts of the forest, that is, perturb it in a systematic way, and then see what happens.''

So Bierregaard and Brazilian authorities approached the pioneer farmers in the area, who agreed to cooperate.

The farmers cleared their pasture lands in a way that left several patches of isolated forest ranging from 2 1/2 to 2,500 acres. And for the past 4 1/2 years, Bierregaard's charges have tramped throughout these living laboratories - digging, measuring, taking temperatures, and just watching and waiting for results.

Just this year, observations have turned into hard data. And some of the results have been surprising.

More than 21,500 bird captures indicate that, when confronted with ''trespassers,'' a number of dominant bird species in the cramped forest patch perish or flee. Apparently the birds spend so much of their time defending their turf they have no time to feed themselves.

Although scientists expected tree reproduction to slow down or, at worst, stop in isolated reserves, findings from one smaller forest area have been startling:

A three- to fourfold fatality rate, evidently caused by the severe effects of extreme exposure to sun and wind.

In one 2/2 acre reserve, ''We watched two Saki monkeys starve to death in a very short time,'' Bierregaard says.

The monkeys had exhausted the mature fruit in the suddenly truncated area and ate ''greener and greener fruit'' rather move to another spot.

''We are probing some basic biological questions here. Why do some species survive and some perish?'' Bierregaard says.

Participants in the jungle project are convinced that their findings will do more than edify the scientific establishment.

Wilson Spironelo's soil samples, for example, may hold clues to why this lushly vegetated forest is apparently so unstable in nutrients - information that could prove invaluable for Brazil and other countries pushing to colonize the Amazon and other tropical forests.

And Lee Harper's army ant colony, transferred to a species-poor woods area, could be the instrument for preserving certain birds that feed off insects stirred up when army ants are present but that vanish when army ants do not live in the area.

Likewise, governments and wildlife managers will be able to present hard data in their effort to establish and design national parks.

Most of all, the experiment could be science's only way to brace for what looks to be an inevitably drastic future.