"Individual lemurs, under study for many years, would be there one day and gone the next," commented Deborah Overdorff, a primatologist at the University of Texas in Austin, who has worked alongside Dollar in Madagascar.
"The threat of predators is a key selection pressure on primates," she added. By studying the island's most significant lemur predator, Dollar has helped put together the entire picture of threats those primates are facing.
Understand and Conserve
Since 1996 Dollar himself has had many encounters with the fossa in Madagascar's Ankarafantsika National Park. For the last eight yearswith help from graduate students and volunteers provided by the conservation charity Earthwatch Institutehe's perfected methods for capturing the animals with both automatic cameras and wire cages.
Trapping fossas gives the team opportunities to weigh and sex the animals, and give them a quick health checkup. Diseases, such as rabies, introduced to the island with domestic dogs and wild cats, now threaten the fossa.
Radio collars reveal how far fossas range (up to 25 kilometers or 16 miles a day). And genetic and scat analysis provide further data on what a fossa's diet consists of, for example.
The data Dollar's team has collected is being used not only to better understand but also to conserve the endangered animal.
Just 8 percent of the intact forest that existed before people arrived on Madagascar remains today. Fewer than perhaps 3,000 fossas cling on in these undisturbed habitats, according to Dollar's estimates.
Currently Dollar is focusing on the competitive threat that two introduced predatorsan undetermined species of wild cat and the Indian civetare posing to the fossa and other native carnivores.
Fossa research has also generated spin-offs in the form of local development and ecotourism, Dollar said. These activities bring money into the poverty-stricken region (where most people survive by subsistence farming) for perhaps the first time. Local people are this year building bungalows in the park, which will provide the first permanent lodgings for tourists to stay in, he said.
Humans have had a profound impact on Madagascar since they first began to arrive from Asia and Africa approximately 2,000 years ago. The huge island is around twice the size of Arizona and sits east of Mozambique in the Indian Ocean.
Madagascar's unique history goes some way toward explaining its unusual collection of 200,000 or more plants and animals. Many of the island's creaturesincluding the fossa, smaller carnivores, and around 35 species of lemurare found nowhere else on Earth.
The viverrid family (to which the fossa belongs) is an ancient line of carnivores. Viverrids are thought to pre-date wolves, cats, hyenas, and other lineages of meat-eatersnone of which are natives of Madagascar, Dollar said.
"Madagascar has been called the eighth continent, and biologically speaking, that's a great name," said Stuart Pimm, Dollar's supervisor and the Doris Duke Chair of Conservation Ecology at Duke University. "The species are not just varieties of African birds and plants but entirely new families," he said. "Madagascar really is a whole new world."
The island is thought to have broken away from Africa and South America, which were joined as a single continent 150 million years ago, carrying with it an assemblage of primitive plants and animals. Early carnivores, primates, and other mammals may have drifted ashore on rafts of vegetation in the years that followed and evolved in virtual isolation until relatively recently.
Madagascar's first explorers, who arrived some 2,000 years ago, would have encountered a ten-foot-tall (three-meter-tall) flightless bird, along with lemurs as big as gorillas and baboons.
Most of these giants became extinct soon after man's arrival, said Pimm, who is also a member of National Geographic's Committee for Research and Exploration. "What we see today is only the remnants of a diverse and fascinating group of animals."
These long-gone wonders might explain why the people of Madagascar are often afraid of the fossa today, Dollar added, though the animal presents little threat to humans.
Bones and other remains show that another larger species of fossa once prowled the forests of Madagascar. That tiger-size mongoose relative (Cryptoprocta spaelia) would have weighed more than 225 pounds (100 kilograms) and "could definitely have taken people," Dollar said.
Dollar still sets up camera traps in remote and unexplored patches of forest in the "wild hope" he might yet discover one alive.
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