Snails favor the karst and absorb some of its calcium to strengthen their shells. Small beetles and cockroaches feed on the thick layer of guano deposited in the caves by bats and in turn serve as food for other predators.
Scientists have yet to identify a new fish found in shallow pools in a cave called Sungai with a tall, vaulted ceiling. The fish, which looks like a small catfish with clear skin, did not respond to flashlights and appeared to be blind.
Many species inhabiting the cool, dark caves have evolved deadly poisons to ensure that they catch their prey, the surveyors said.
"It's a straightforward carnivore system," Salas said. "Some of the most spectacularly horrendous insects live in caves."
Because of its inaccessibility, "most of this area isn't hotly contested," said Scott Stanley, the Conservancy's program manager for East Kalimantan. Still, the Indonesian government has authorized large logging concessions around the karst areas and failed to curb widespread illegal logging.
Conservationists say the logging, in addition to directly destroying habitat for many species, increases the risk of fires that compound the ecological damage. Once giant hardwood trees that top the canopy in lowland forests are cut down, the entire ecosystem changes, becoming less humid and more susceptible to fire.
The Conservancy is hoping to use evidence of the rich biological diversity here to encourage the government to develop and enforce a conservation plan.
Despite the effects of logging and fire, the remaining patches of old-growth rain forest outside the caves still house one of the most diverse arrays of species anywhere. Visiting researchers and several Indonesian scientists who joined the expedition have located dozens of insects that have never been catalogued.
"These are the animals that nobody's interested in," Vermuelen said. "But they make up the largest number of species in the world. Eighty percent have no name. Nobody's ever seen the things."
Scientists are concerned, however, that they have not found certain "indicator species" here. This could be a sign that the fires have permanently damaged the health of the fragile ecosystem. At one site along the emerald waters of the Marang River, the fires -- which flared again in 2002 in some areas -- destroyed the softwood trees favored by woodpeckers.
"Here, the only trees that are standing are those that have very hard woods," said Mas Noerdjito, an Indonesian biologist who studies birds at the government's national research facility. "There is only one species of woodpecker here." Also mostly absent were large dying trees whose hollow trunks provide nesting areas for some bird and bat species.
Nor were there many rats or squirrels -- which serve as "architects" by spreading seeds around the forest.
Environmentalists fear that one of the world's largest tropical rain forests, surpassed only by those in the Amazon and the Congo, is in great peril -- along with the array of plant and animal life it supports.
"This is probably getting hit the hardest in the world," Stanley said.
