Rarest of the Rare - conservation of the Javan rhinoceros
Dense stands of bamboo commingle with spiny rattan and an occasional small tree to form a low, prickly jungle. This is an area almost devoid of trails, much less anything so accommodating as a road.
In the dry season, the land is parched. During the other 9 months of the year, the heavens dump rain continually, creating swamps in the lowlands and steamy, slick hillsides elsewhere. And oh, those hills--not high so much as endlessly undulating. Traversing them puts a constant strain on leg muscles.
Mosquitoes ply their blood-sucking trade, in the process often infecting trekkers with the infectious agents responsible for dengue fever, malaria, or Japanese encephalitis. Huge leeches stealthily attach themselves to passersby, hoping to crawl up to a warm meal on someone's leg or perhaps neck. At bedtime, as rare travelers string their hammocks in this jungle, a snarl might pierce the dark, signaling that a tiger is on the prowl.
Surveying this area on foot is not most people's idea of a walk in the park. Yet that's exactly what conservation biologists and park guards sign up for when they come to Cat Loc, a portion of Cat Tien National Park in southern Vietnam.
Those who patrol this formidable terrain are protecting what is arguably the most endangered mammal on earth. In this 6,200-hectare portion of the park resides the last surviving remnant of Javan rhinos outside Indonesia.
Following the Vietnam War, scientists assumed that this subspecies was extinct--until the carcass of a poached animal turned up in a local market stall in 1989. Since then, scientists have been trying to protect Vietnam's elusive pocket of survivors.
There aren't many Javan rhinos in the park, and in fact, none of the intrepid conservationists has ever seen one here in the flesh. Last year, an indirect census based on hoofprints pegged Vietnam's population at only five to eight rhinos. Still, that may constitute almost 15 percent of the species' global population--and a sizable share of its biodiversity.
Several conservation groups and government agencies, including the U.S. Fish and Wildlife Service, argue that there's an urgent need to safeguard this rhino from further threats. All acknowledge that the effort will be an uphill battle. At a minimum, government officials and biologists must weigh some politically charged tradeoffs if they hope to spare this creature from extinction.
The Javan, or lesser one-horned, rhino (Rhinoceros sondaicus) once thundered throughout Vietnam, Laos, Cambodia, Thailand, Burma, and Indonesia. Primarily a lowland dweller, populations even extended into India. In the mid19th century, "this rhino could be found 20 kilometers from where Calcutta is now," notes Java-based conservation biologist Nico van Strien of the International Rhino Foundation (IRF), with headquarters in Cumberland, Ohio. He and other biologists were invited by the Vietnamese government to develop a rhino-conservation plan.
Today, all rhinos are endangered owing to centuries of hunting--both to fill trophy cases and to supply folk medicine's demand for rhino horns, which traditional Oriental healers still prescribe as an aphrodisiac (SN: 11/17/79, p. 346). In the most dire condition are the Javans, barely holding on with some 60 animals, and the Sumatran rhino (Dicerorhinus sumatrensis), with perhaps 300 individuals, all in Indonesia.
Poaching of both rhinos is now largely under control, so human encroachment and poor habitat are emerging as leading constraints on each species' recovery. Nowhere is this more evident than in Vietnam.
At about the same time the Vietnamese government made Cat Loc a rhino refuge in 1992, it designated this and the surrounding forested region a "new economic zone." In essence, the authorities invited citizens, especially ethnic minorities from crowded regions in northern Vietnam, to farm the area. People responded in droves, notes IRF program director Tom Foose.
Some immigrants took up rice farming; many others cut down forest to establish cashew plantations. Though illegal, rattan harvesting in the park also developed into a thriving trade.
Villagers' migration and activities have reduced the rhino's habitat to about 15 percent of its area in 1990, Foose reports. Some 16,000 people now live right outside Cat Loc's forest--which, he notes, is the only area of Vietnam where rhinos remain. Another 200 people have actually moved inside the park's rhino territory, reports Gert Polet of the World Wildlife Fund-Vietnam, speaking by phone from Cat Tien, 150 kilometers north of Ho Chi Minh City.
These local farmers tend to be very proud of the rhinos, says Polet, who heads the Cat Tien Conservation Project. Unfortunately, he adds, "the farmers are also very poor, and their making a living these days involves cutting down forest."
What remains of the forest is no picnic for the animals, he adds. Javan rhinos prefer to eat shrubs, small trees, and the occasional mouthful of grass. Defoliants sprayed by U.S. planes during the Vietnam War, however, largely eradicated what had been the rhino's dietary staples. The bamboo and rattan, which quickly filled in the forest, remain.
On the basis of hoofprint measurements, Vietnam's rhinos are only about two-thirds as big as members of their species in Java's Ujung Kulon National Park. While this difference might be genetic, Polet notes that the diminutive stature of Vietnam's rhinos may also reflect their poor diet.
Though Polet would love the opportunity to measure a Vietnamese rhino, he'd settle for just laying eyes on one. To date, he and others working at Cat Loc have had to content themselves with poring over low-contrast, mostly nighttime flash photos of the animals captured by cameras set up last May.
Polet's team identified 10 places in the park where rhinos were likely to wander, based on habitat and dung sightings. On strategically placed trees at each site, they mounted cameras and infrared sensors that trigger the shutters.
Every 2 weeks, park guards laboriously trek to each camera to exchange film. The first rolls from four of the cameras yielded a total of seven portraits--the first-ever photos of live Vietnamese rhinos. In the intervening months, however, none of the cameras has caught another rhino on film. It almost appears, Polet says, as if the cagey critters are out to sabotage the system. Where hoofprints appear, they're now behind the trees bearing cameras. Several infrared sensors have also been roughed up and shoved out of alignment, presumably by the rhinos.
Polet's hope is that photos from cameras placed in varying locations eventually will provide a noninvasive means of surveying the population over time, offering not only portraits of individuals, but also information on size, gender, and reproduction.
In the next few months, dung should also emerge as a rich source of information on these elusive populations, according to Don J. Melnick of Columbia University in New York City.
For the past several years, Melnick has been fingerprinting DNA from the dung of rhinos and other endangered species. Not only do these data identify an animal's gender, but they also permit analyses of the degree to which individuals' genetic blueprints diverge.
Conservation biologists have begun using such analyses to help them manage disappearing pockets of various endangered animals. Under a U.S. Fish & Wildlife Service grant, researchers in Melnick's lab are working out methods to analyze dung from Javan rhinos. They are working with dung from Indonesia and have arranged for specimens to be sent from Vietnam within the next few months.
"There are two measures of a population," Melnick explains. A census tallies how many individuals exist. As important to species conservators managing recovery of populations is the effective population size--how many animals have relatively dissimilar sets of genes. If the same individual fathered many of the animals in a group, the effective population size would be significantly smaller than the census indicates.
Melnick notes that conservators often are tempted to move animals between groups to maximize their reproduction. If almost all of the seven or so Vietnamese rhinos prove to be male, for instance, biologists might consider airlifting in a few females from Java's Ujung Kulon reserve.
Yet, important adaptations to endemic diseases or other aspects of each population's local environments may underlie any genetic distinctions between the two populations--already considered separate subspecies of R. sondaicus. Introducing genes from one group to the other might therefore render future generations of this beleaguered species even less fit, Melnick worries.