The hunters carry AK-47s. Along stream beds, unexploded ordnance pokes through the encroaching jungle. Villagers use shell casings for planters and have made fish ponds in the craters left by 500-pound bombs that blew up long ago.

Back then, the paths that wound through the Annamite Mountains were known as the Ho Chi Minh Trail--the backwoods supply train for communist insurgents during the Vietnam War.

Today, the Annamites, which mark the border between Vietnam and Laos, are rapidly gaining notice for another reason. Since 1992, scientists working there have found six large mammal species that had either never been seen before except by local people or were believed to be extinct.

In a world that supposedly had few such secrets left, the Annamites are rapidly becoming a zoological El Dorado: "It's always amazing to find a big animal that nobody's ever seen," said the Wildlife Conservation Society's George Amato, who conducted DNA testing on many of the new species.

"In these remote areas of Asia, mostly because of the war, we don't have any surveys," Amato continued. "Perhaps the Annamites shouldn't have been such a surprise, except that it's such a large number."

The discoveries began in 1992, when Western scientists in the central Vietnam Annamites heard about a 200-pound cow-like animal unlike any other on Earth. Others have since been reported in Laos, and several have been captured. Laotians call them saola--or spindlehorns. This "false oryx" represented an entirely new mammal genus.

Since then, scientists on both sides of the border have documented the existence of three other species never before seen outside the region: a striped hare; a giant muntjac, or barking deer, that weighs about 75 pounds; and a much smaller Truong Son muntjac, from the Truong Son range of the Annamites, that weighs about 35 pounds.

In addition, researchers have rediscovered Roosevelt's muntjac, first described during a 1929 hunting trip by former president Theodore Roosevelt's sons, and a wild pig, known as a warty pig or yellow pig, reported by a missionary at the end of the 19th century.

To give a sense of the significance of these discoveries, scientists note that the number of new or lost large mammal species encountered in the Annamites in the past decade equals the number found in the rest of the world during the entire 20th century.

"And it's not just that they're new, it's that what we're finding is very different," said Josh Ginsberg, Asia program director at the Wildlife Conservation Society. "These are very unusual animals."

The World Wildlife Fund's Steve Osofsky, senior program officer for species conservation, said the recent successes are largely "an access issue," noting that Vietnam and Laos were closed to Western scientists until recently. The Laotian government did not let outside researchers into the country until 1992.

Also, continued Osofsky, Vietnam and Laos have become interested in conservation and wildlife habitat in recent years. He noted that the first photographs of Vietnam's rare Javan rhino, taken by tripwire camera in a game preserve north of Ho Chi Minh City last summer, prompted a huge outpouring of national publicity.

Still, Ginsberg said, access is not everything: "The critical question we're kicking around is whether we are finding species only because [the region is] unexplored, or is there something interesting about the Annamites?" Ginsberg said. "I think the answer is both."

The Wildlife Fund's Eric Wikramanayake, one of the researchers who reported the discovery of the Truong Son muntjac last year, explained that the Annamites have areas of lowland dry forest interspersed with areas of highland rain forest that over time have isolated pockets of habitat for individual species.

The Annamites, rising to more than 8,000 feet in some places, extend for more than 700 miles down the spine of Indochina along the entire length of the Laos-Vietnam border.

Wikramanayake said scientists theorize that during ice ages beginning about 1.8 million years ago, the mountains alternated between relatively cool and dry periods when the sea receded, followed by warmer and rainier periods when the ice melted and the sea level rose.

During the wet periods, animals migrated freely; during the dry periods they were stuck in their mountain oases: "As climates fluctuate over time, sometimes species that were more widespread become more isolated," Amato said. And in isolation there is genetic drift and differentiation, leading to new species.

Alison K. Surridge, of Britain's University of East Anglia, noted that a rabbit similar to the striped hare she described in August in the journal Science has a distant cousin in Sumatra, as does the warty pig, suggesting that the two species may have had common ancestors when land bridges linked what is now Indonesia to the Asian mainland.

During the Indochina wars, the Annamites were the target of bombings as the Western allies tried to halt the flow of weapons and supplies from North Vietnam to guerrilla insurgents fighting in the South.

Today, Wikramanayake said, evidence of the war is everywhere, with craters, downed trees and unexploded ordnance dotting the countryside. Hunters have ready access to assault rifles but use them sparingly because of a shortage of ammunition, he said. Instead, they kill their prey with snares and tripwire deadfalls along mountain game trails.

Ginsberg said the region is under considerable stress. Hunters from more populous Vietnam are crossing the border into Laos to capture animals to ship to China or to kill and export body parts for use in Asian folk medicine.

In underpopulated Laos, the animals fare better, except that many of the highland people still practice slash-and-burn agriculture, torching sections of old-growth forest to plant upland rice and other crops. Saola and barking deer thrive on fruit-bearing trees in the old forest.

Furthermore, the Annamites are "a very poor area and the people have to hunt the animals to feed themselves," Surridge said. "Local people are traveling farther and farther into the forest to find food."

Indeed, although live striped hares have been photographed in camera traps, the first samples found by Surridge's researchers were hanging in a local meat market. Wikramanayake identified the Truong Son muntjac from dried skulls tacked up on the walls of a hunter's cottage.

And the Wildlife Conservation Society's George B. Schaller bought part of a warty pig hanging in a mountain smokehouse, ate it for dinner, saved the bones, had them tested and rediscovered a long lost species. A live adult warty pig has never been documented in the wild.