On the trail of the scientists who make the trails

Deep in the tropical rain forest, a small fruit-eating bat carefully nicks the veins on the underside of a philodendron leaf, causing the edges to fold down like a miniature tent. The bat curls up under its little tent and goes to sleep. Other bats don't make tents, why do these?

In "The Tapir's Morning Bath," journalist Elizabeth Royte follows field biologists into the rain forest with a similar question: Other people, after all, do not feel compelled to sit up all night being bitten by mosquitoes, ticks, and chiggers. Why do these?

The Panama Canal is made up of a channel leading inland from each coast, joined by an immense manmade lake that covers what was once a rain forest. Numerous islands dot the lake. In the 1920s, a group of foresighted scientists managed to have the largest, Barro Colorado, with its nearly intact tropical forest, set aside as a scientific preserve.

In these pages, the present-day researchers of Barro Colorado spring vividly to life. Royte follows a young biologist from UC Berkeley, as the biologist follows a troop of spider monkeys.

Studying monkeys like this entails long days of trailing the agile little creatures as they skitter through the treetops, clambering easily from branch to branch. For an earth-bound researcher, keeping up with the troop entails scrambling up steep ravines, pushing through tangled undergrowth, and skidding down hillsides slick with rain. The early weeks are especially frustrating, as distrustful monkeys shy away from the interloper.

Royte, a New York journalist, is as much an interloper on the island as this scientist is among the troop of monkeys. The scientists, after all, have paid their dues to get here. They have spent years in graduate school, and they reach Barro Colorado only after their laboriously planned studies survive rigorous review to be selected for funding.

But Royte ingratiates herself by offering to help. On the island, these scientists work long hours, and conversation can be larded with arcane jargon incomprehensible to an outsider. She's willing to wade through this - and the muck of mangrove swamps - to hang insect traps on branches and sit on the forest floor counting the number of leaf-cutter ants that march past.

As they whiz across the lake in a Boston whaler, Royte is determined to pursue her subject at full throttle, even as the distinguished biologist perched in the bow tries to net moths without falling overboard. He shares his excitement about the natural world in all its magnificent complexity.

For instance, he tells her, urania moths migrate annually. Some years, however, only a few hundred appear. Other years, several hundred million moths fly past the island. No one knows where they come from or where they are bound. In Royte's retelling, scientific enthusiasm is infectious. Soon we, too, want to know what drives these winged nomads.

Readers will come away from "The Tapir's Bath" with an appreciation of the way narrow research questions become the material from which useful knowledge is constructed. But don't read it for that.

Read it for the thrill of the chase. Will the young researcher from Berkeley who has trudged the forest for three days without so much as a glimpse of a non-human primate ever locate her spider-monkey troop? Will the German biologist whose sophisticated equipment fails manage to contrive an impromptu method to measure the effect of leaf-cutting ants on the trees they harvest? And will the PhD candidate from the University of Michigan astound his professors by synthesizing a new theory to explain why biological diversity decreases with distance from the equator, or fulfill their expectations by failing even to discover why bats make tents?

And just why does a tapir take a morning bath?

Diana Muir is the author of 'Reflections in Bullough's Pond: Economy and Ecosystem in New England' (University Press of New England).