Martha's equanimity around people may have been genuine, but she died just 18 days after her capture. It was then that zookeepers discovered that she had been pregnant. But they could not determine her cause of death. The handful of other saolas that have been taken into captivity also perished quickly. In June 1993, hunters turned over two young saola to Tuoc and his colleagues in Hanoi. Within months, the pair succumbed to infections.
The saola's baffling fragility underscores how little is known about its biology or evolutionary history. Robichaud and conservation biologist Robert Timmins have proposed that saola were once widespread in the wet evergreen forests that covered Southeast Asia until several million years ago. These forests receded during cool, dry ice ages, leaving just a few patches suitable for saola. "If we leave the saola alone," says Tuoc, "I think—no, I hope—it will survive."
Other scientists argue for hands-on assistance. Pierre Comizzoli of the Smithsonian's Center for Species Survival says a captive breeding program is the only option left to save the saola from extinction. He teamed up with scientists from the Vietnamese Academy of Science and Technology in Hanoi on a survey late last year to find possible locations for a breeding site.
"It's a sensitive topic," he acknowledges. "But captive breeding doesn't mean that we are going to put saolas in cages, or do industrial production of saolas." Instead, he envisions putting an electric fence around a select swath of saola habitat, perhaps half an acre. "They would have access to their natural environment and could feed themselves, and at the same time we could start to study them," says Comizzoli, adding that something as simple as fresh dung would be "fantastic" for research purposes.
After fording the river, Tuoc and my family and I hike to a ranger station. The next leg of our journey is on motorcycles. Their make, Minsk, is emblazoned in Cyrillic on the gas tank. Our sons, sandwiched between my wife and a ranger, have never ridden a motorcycle before, and they squeal with delight. For several miles, we tear uphill on an empty, curvy road faster than this anxious parent would like. At the end of the road, we hike into the misty hills on our quest to spot a saola.
Preserving this habitat will help a host of other rare creatures, including the two other new mammals in Vietnam that Tuoc helped uncover, both primitive kinds of deer: the large-antlered muntjac, in 1994, and the diminutive Truong Son muntjac, in 1997. Strange beasts continue to emerge from these forests, including the kha-nyou, a rodent identified in 2006 as a species thought to have been extinct for 11 million years. "If we lose the saola," says Long, "it will be a symbol of our failure to protect this unique ecosystem."
At Pu Mat, the late morning sun is burning off the mist. With the spry Tuoc leading the way, we clamber up a slick path until we reach Kem Waterfall. Tuoc grabs a handful of broad, dark-green leaves near the entrancing falls. "Saola like to eat these," he says. "At least, we have seen bite marks." These Araceae leaves, I realize with a pang, may be as close as I ever get to a saola. Tuoc, too, has no delusions. "Maybe I'll never see one in the wild," he says.
Richard Stone is the Asia editor for Science magazine. He lives in Beijing.