Net work: Scott Loarie of Stanford, left, weighs birds, while Costa Rican Dionisio Paniagna-Castro tags them at Las Cruces. All photos by Chris Hildreth.
Net work: Scott Loarie of Stanford, left, weighs birds, while Costa Rican Dionisio Paniagna-Castro tags them at Las Cruces. All photos by Chris Hildreth.

Where the Exotic Meets the Academic

In Costa Rica, scientists revel in biological drama and ecological mysteries through the Organization for Tropical Studies, now celebrating its fortieth anniversary.
August 1, 2003

Nature rules this place, and with a mahogany fist. She has decreed this forest to be no gentle glade, but a biological battleground, where each species fights for her favor. All the creatures great and small employ their own offensive tactics. Strangler figs wrap their roots around the mammoth trees, thrusting branches upward toward the light. The trees duel for their place in the sun, crushing younger offspring with massive plummeting branches and stifling them beneath light-blocking foliage. And the animals—goldenrod-yellow eyelash vipers, ghost-like jaguars, inch-long bullet ants, and deceptively dainty poison dart frogs—all wield their own weaponry to protect and to kill.

Even the water seems a liquid life form. Like an insect metamorphosing from egg to larva to adult, moisture here can transmute from a steamy, smothering humidity, to a gently pattering shower, to a roaring deluge that drenches the forest. In mere hours, the downpour can turn a river from a placid stream into a roiling brown flood that sweeps away massive logs as if they were twigs.

This is La Selva Biological Station of the Organization for Tropical Studies (OTS)—3,900 acres comprising a diversity of life that is a microcosm of the awe-inspiring ecological wealth of the tropics, in general, and Costa Rica, in particular. The scientists here revel in La Selva’s biological drama—and in its profound scientific mysteries. Living within the station’s thick forests are 1,700 plant species—460 species of trees alone; more than sixty species of bats; 463 species of birds; and 600 species of ants. The station boasts some 7,000 species of butterflies and moths, fully half the number of species in the entire North American continent north of Mexico.

Lighting bugs: Jadranka Rota selects specific moths for specimens at a collecting station in La Selva

Lighting bugs: Jadranka Rota selects 
specific moths for specimens at a collecting station in La Selva.

As a sprawling international consortium of some sixty-five universities and research institutions, OTS is among the world’s most successful organizations for fostering tropical research and education. The center’s biological stations attract hundreds of visiting scientists every year to study tropical ecology. And OTS sponsors courses to teach students, park managers, and policymakers about tropical ecology and conservation science and policy. OTS has maintained its U.S. headquarters at Duke since 1976, when Donald Stone, now professor emeritus of biology, became the organization’s executive director. Under Duke’s agreement with OTS, recently extended for another half-century, OTS staff members are classified as Duke employees, and the organization’s researchers can hold adjunct positions at the university.

La Selva is one of three Costa Rican research stations operated by OTS. The others are at Las Cruces and Palos Verde. The organization is also planning a new academic center at the University of Costa Rica and is looking for ways to export its model of research and teaching to countries in Africa and Asia by joining with local universities, wildlife parks, and conservation organizations.

At all of OTS’s biological stations, visiting biologists do science across the breadth of space, time, and technology. They take scientific measurements throughout its thickly forested landscape, hoist themselves into its treetops, and sink cores deep into its sediments. They rouse themselves as the earliest morning light filters down through the luxuriant green foliage and work long into the night, their puny headlamps attempting to hold back the utter blackness that shrouds a nocturnal rain forest. And, they use implements ranging from the most basic rubber boots to the latest in digital computer imaging.

The discoveries they have made here range from the poetically inspiring—a new butterfly or ant species—to the darkly disquieting: hints that the global increase in carbon dioxide could decimate tropical forests.

GARY HARTSHORN, President, Organization for Tropical Studies

“Many ecologists have learned that long-term data sets that span decades are extraordinarily valuable. We have projects that have been going on here at La Selva for up to forty years.”

GARY HARTSHORN, President, Organization for Tropical Studies

Last April, OTS’s leaders and researchers gathered to observe the organization’s fortieth anniversary with a banquet, a symposium on the future of tropical science, and a “rubber boot camp” field experience. One boot camp found a group of timorous, amateur biologists trailing a stalwart young graduate student into the forbidding gloom of a tropical night to trap bats. The mission was to track the bats’ movements and hunting and feeding habits. The nocturnal excursion gave a fascinating taste of what it takes to be a bat researcher, which includes some rather unexpected skills. The novices learned to untangle a wispy “mist net” and string it across a trail in the pitch-black darkness, as if preparing for some exotic, tropical badminton game. But in this case, the shuttlecocks were squirming, squeaking balls of fur, ill-tempered at being interrupted on their nightly feeding flights by becoming tangled in a net—extremely tangled, in many cases. The novices had to learn the delicate art of extricating a bat from a snarl of fine nylon while avoiding the creature’s angry nips.

The effort yielded a fantastic harvest—dozens of gorgeously ugly bats for examination by the group. There were tiny, snowball-like, Honduran white bats, which spend their days nestled beneath banana leaves, whose veins they snip to fold over themselves like sleeping bags. And there were the sharp-toothed vampire bats, masters of the stealthy art of gliding up to animals and opening a tiny wound to drink their blood. Each of the bats was measured and weighed, and then offered a dollop of banana baby food as recompense for the indignity of capture. They stuck out tiny, unexpectedly pink tongues to lap up the treat. Afterward, they were carefully transferred to a nearby branch, where they hung like bizarre ornaments on an Addams Family Christmas tree, until they recovered and flew away.

Water world: Dorothy Boone of Emory gets her feet wet collecting snails in Palos Verde


Water world: Dorothy Boone of Emory gets her feet wet collecting snails in Palos Verde.

At the OTS’s fortieth-anniversary symposium, the group celebrated such educational and research successes, but also pondered how to apply twenty-first-century science and education to the massive challenges of understanding and saving the planet’s tropical ecosystems. “The last several decades have revealed that the diversity of life is far greater than we had even imagined,” said E.O. Wilson, a renowned biologist and one of OTS’s founders, speaking at the symposium. The vast majority of species are concentrated in tropical forests, he said, and are being destroyed at an alarming rate, potentially “inflicting a heavy price on future generations in economics, in security, and in spirit.”

He and his fellow biologists are proposing a massive international “systematics” project to catalogue the approximately 90 percent of the millions of Earth’s species that remain unknown. The result of the multi-decade effort, which he hopes will be funded by governments worldwide, would be an online “encyclopedia of diversity.” Without such a catalogue, Wilson said, we have no way of even knowing what we are in danger of losing.

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Fang face: the vampire bat, one of nearly 
65 bat species in Costa Rica.

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Red menace: the strawberry poison dart 
frog, whose deadly toxin is used on hunting arrows.

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Danger under glass: a scorpion is examined 
in the safest possible way.

To OTS President Gary Hartshorn, OTS and its scientific stations will play a central role not only in cataloguing species, but also in understanding their role in the intricate web of ecology. A fundamental advantage of such stations is their longevity, he says. “Many ecologists have learned that long-term data sets that span decades are extraordinarily valuable. Because of the initiative of OTS and of individual researchers, we have projects that have been going on here at La Selva for up to forty years, and these are hugely important and very valuable.”

A prime example of the value of such long-term data is the record of the growth of La Selva’s massive trees, maintained by ecologists David and Deborah Clark for nineteen years. “If someone new wants to work on trees at La Selva,” Deborah Clark says, “she or he doesn’t have to come in and start from scratch and say, ‘What is this species? When does it produce seeds? Who eats it? What does it need to regenerate?’” Instead, researchers “can come in and build that fundamental knowledge base in a very quick time frame and get to what we often say are the much more interesting ecological questions there.”

The latest discovery by the Clarks, who are ecologists at the University of Missouri-St. Louis and former scientific directors of La Selva, dramatically illustrates the scientific value of such data. Every year since 1984, the Clarks and their Costa Rican and U.S. colleagues have made painstaking measurements—precise to less than a millimeter—of the growth of La Selva’s giant trees.

These measurements recently revealed a startling discovery: During warmer years, the trees grew less and expelled more carbon dioxide. “A major, tacit assumption, I think, of 90 percent of us working at La Selva was that we were working in a tropical rain forest, which means equitable climate, which means every year’s the same,” says Deborah Clark. However, the new finding “made it very clear to us that, if our forest is very sensitive to small, inter-year differences in climate, it’s certainly going to be affected with these global changes going on right now.” The world’s climate could be entering what she calls “very scary territory,” in which the rise in global temperature, along with accompanying drought, could inflict enormous damage to tropical forests and increase the amount of carbon dioxide in the planet’s atmosphere.

Many ecologists had assumed that tropical forests would grow faster with higher levels of carbon dioxide, buffering the global increase in the greenhouse gas. In contrast, the scenario the Clarks’ research hints at has been ominously named the Armageddon Model. More research is needed to understand how old-growth trees take up or release carbon, and that is one way that a facility like La Selva is invaluable, she says. “The long-term nature of our research means we simply could not have done it outside of a long-term, protected site like La Selva. And a lot of the things that we discovered could only have been done with the kinds of tools that are available at La Selva.”

These tools include the usual scientific amenities such as air-conditioned analytical laboratories, computers, and high-speed Internet connections. Also, surprising to visitors, who only perceive a confusing tangle of forest, La Selva is meticulously surveyed, with some 3,000 marker posts that enable researchers to locate and correlate their study subjects precisely.

A computerized geographical information system makes it possible to overlay data from one scientist—on tree species, for example—onto data from another on, say, ant populations. These correlations could yield important insights into the weave of the intricate web of tropical ecology, in which one organism may affect the survival of another. The presence of ants in a certain area, for example, could give insights into the ecology of vegetation, and vice versa.

Many visitors are also startled by another anomalous feature of La Selva—concrete sidewalks winding their way through the thick forests. The sidewalks have proved a highly useful component of La Selva’s scientific infrastructure, says Hartshorn, the OTS director. They enable scientists to pedal the station’s bicycles far into the forest depths to carry scientific equipment and collect data. And, oddly enough, the concrete sidewalks prove less damaging to the environment than the vegetation-crushing, muddy trails researchers had to slog in the past.

In the future, less visible forms of data collection will become available when the station installs a planned wireless computer network, enabling remote instruments to “report in” by themselves, thus making it unnecessary for a technician to retrieve data in the field. Hartshorn and his colleagues plan to use this technology to the fullest in such new research efforts as the Tropical Ecology Assessment and Monitoring (TEAM) project, which will involve years, possibly even decades, of detailed ecological measurements across La Selva and into the neighboring Braulio Carrillo National Park. “There are major and exciting scientific questions about how forest structure and composition change with elevation, and how animals might migrate across large regions,” says Hartshorn..

In addition to the latest in computer technology, tropical biologists are eagerly adopting the latest in genomic research. In fact, the forensic experts of TV’s popular Crime Scene Investigation (CSI) might soon be rivaled by those at “TSI”—Tropical Scene Investigation. Tropical biologists are beginning to use the same genetic-fingerprinting techniques to identify new species that CSI sleuths use to nab criminals. Individual insect parts, feathers, scales, toenail-clippings, and other minute tissue samples can be analyzed to pinpoint the genetic identity of an animal, said Pedro Le--n, a tropical biologist, at the OTS symposium. With social insects, which live in interdependent colonies, “this is quite nice, because you can sample a few animals without being concerned about major impact on the population,” said Le--n, a University of Costa Rica professor and former chair of the OTS board of directors. This kind of data will enable researchers to identify how individual animals and plants are related to one another, and how they spread. The genetic data can also help organize the multitude of species on the phylogenetic tree of life by comparing genetic data among them.

Las Cruces: the place for dining at dusk

Las Cruces: the place for dining at dusk.

Stepping lightly: a leaf-footed bug

Stepping lightly: a leaf-footed bug.

Hot stuff: the flower of a torch ginger in Las Cruces

Hot stuff: the flower of a torch ginger in Las Cruces.

Yellow means caution: the eyelash viper, one of the most poisonous snakes in Costa Rica

Yellow means caution: the eyelash viper, one of the most poisonous snakes in Costa Rica.

Perhaps most dramatic, said Le--n, will be the “shotgun approach” to genomic identification of organisms. Scientists can take a soil sample and isolate the DNA of a multitude of unknown species. By analyzing the genes contained in the DNA, eventually the scientists will be able to determine the identities of the unknown organisms.

The necessarily abbreviated rubber boot camps held during OTS’s fortieth anniversary celebration provided a tantalizing taste of the experiences of undergraduate and graduate students who attend summer- and semester-long field courses in tropical biology and ecology sponsored by OTS at all three of its stations.

For biology major and Duke senior Jennifer Rainey, the OTS tropical biology course she took in the summer of 2002 was a rigorous lesson in the realities of field research. As her independent-study project, she had chosen to record how white-faced capuchin monkeys at the Palo Verde station care for their young. Little did she suspect that the monkeys would be so, well, active.

Reflecting on the eight-hour days of chasing after monkeys, she declares that it “was really fun and grueling at the same time. At Palo Verde, it gets up to a hundred and twelve degrees, sometimes. So, we’d be out in long pants, long-sleeve shirts running after monkeys through acacia trees and thorns, and it was a mess. You’re not reading about someone who had to work really hard to follow monkeys and get this data—you’re the one getting this data. You’re the one who’s picking the ants off your arms. You’re the one who’s driving yourself out of bed at 4:30.”

Like her fellow students, however, Rainey learned that the effort yielded the kind of immersion in nature that forges scientists out of students. “It’s really neat to be in the park and watching how all the different organisms interact with each other.”

The course crystallized Christopher Martin’s lifelong interest in biology. “I’ve always wanted to be a biologist since I was two years old catching tadpoles,” says Martin, also a senior. He says he was worried that his experience in the wilds of Costa Rica might prove too grueling, that “maybe it’ll be too hot or whatever, but none of that’s true. I’m still a hard-core biologist.”

So hard-core, in fact, that for his research project, Martin explored, with painstaking care, the feeding habits of the ant lion—a peculiar insect that lurks at the bottom of a tiny pit it has dug, waiting for ants to drop in for dinner. “I wanted to look at what makes an ant lion most effective at catching its prey,” he says. “And the main thing I did was to go around with a tweezers and drop an ant in each pit, record whether the ant escaped or was eaten, and then measure the diameter of the pit to get an idea of how big the pit was and measure the size of the ant lion.” While his results did not prove any dramatic theory of ant-lion behavior, they did give him a fascinating glimpse into a peculiar corner of nature.

Martin’s project also gave him some modest notoriety as a talented imitator of the insects—a not-ready-for-Vegas act that involves opening his mouth wide in a perfect imitation of an ant lion waiting for its prey.

For Hartshorn, and many other tropical scientists like him, the education and research afforded by La Selva are only part of the explanation for the lure of the tropics. Thirty years ago, while living in the single crude cabin, La Selva’s only facility at the time, he decided that the rain forest was a place he had to make his home. “I don’t know quite how to explain it,” he says. “For some reason, the La Selva forest just captured me. I became immediately enamored.” And so, he hopes, will countless future generations of students, scientists, and political leaders who hold the fate of the tropical rain forest in their hands.