RIO DE JANEIRO, Brazil -- It haunts the Amazon jungle with a giant bear's body and a monkey's face, clad in dark red fur and trailing a cloud of flying beetles. Its stench is disabling, its upright bulk disconcertingly human-like and its roar like endless thunder.
"When you hear it, you want to move in the other direction," said ornithologist David Oren. "It's absolutely terrifying."
To rubber tappers and Indians in the forest's remote western fringe, the creature is the Mapinguari, the Amazon's version of the legendary Bigfoot. No scientist has ever seen it, but Dr. Oren may be on the verge of proving the mythological animal actually exists.
Scientists in the United States and Germany this month are performing DNA tests on hair and feces that Dr. Oren collected in Brazil's remote Acre state. And if his suspicions are correct, the tests will reveal a biological shocker: The fabled monster is actually a species of giant ground sloth believed extinct for 8,500 years.
"I have every confidence we have found it," Dr. Oren said last week from his offices at the Emilio Goeldi Natural History Museum in Belem, where he is recovering from malaria contracted during his search in November and December.
If he's right, the sloth, believed to weigh more than 600 pounds and stand 6 feet tall, would be the largest land mammal in South America. It also would be powerful evidence of the kind of mysteries the still largely unexplored Amazon basin holds.
"The prospects of finding megafauna like this are intriguing," said Peter Clearly, a spokesman for the Washington-based Nature Conservancy, which seeks to preserve habitat in the Amazon rain forest. "There's no question it would strengthen the arguments for conservation of rain forests in general."
Dr. Oren first heard stories of the Mapinguari 10 years ago while tracking birds in remote regions of the western Amazon.
Rubber tappers, Indian hunters and others told remarkably similar tales about a giant nocturnal red or black creature, proportioned like a man and with a human-like face.
It had backward-turned clawed feet, skin capable of withstanding shotgun blasts and a horrible smell that emitted from a "second mouth" in its stomach.
"Several said they had come face-to-face with the devil itself," Dr. Oren said. "And there are classic stories about it being an Indian shaman who discovered the secret of immortality, but paid for it by being transformed into this horrible monster."
Initially, Dr. Oren laughed off the stories. But the first time he heard an eyewitness account from a reliable source, "a light went off in my head," he said. "It could only be a ground sloth."
For nine years, Dr. Oren kept his suspicions about the Mapinguari to himself. "I'm the first one to admit the whole idea is rather absurd," he said.
But after Amazon dwellers year after year described to him stories of mothers with offspring, the creatures' seasonal movements to find water and even what their feces looked like, he said, "it became quite clear it would be irresponsible as a scientist not to follow up these leads."
So last year, he set off to find the elusive sloth. He never saw one. But he shot videotape of clawed trees, taped what he believes are the creature's minute-long thunderous roars, and made molds of round footprints with backward-facing claws. He also collected hair and 22 pounds of feces, which are being analyzed.
Norman Doggett, a molecular biologist at Los Alamos National Laboratory in New Mexico, says DNA in the hair could be 'D compared to DNA from the blood of living sloths or other cousins of the giant ground sloth .
Based on known mutation rates, researchers could then predict how closely the DNA of the giant ground sloth would resemble its modern kin, and check to see if those resemblances hold up in the sample, Dr. Doggett said.
But Malcolm McKenna, a paleontologist at the American
Museum of Natural History in New York City, says the DNA won't necessarily prove beyond a doubt whether the creature is a giant ground sloth.
The sample could prove adequate only to show it is some kind of sloth, or simply a mammal. And of course the hair itself could be a fake planted for Dr. Oren to find, noted the self-professed skeptic.
"I'd be delighted if he found [the sloth]. I'd love to see one led in here on a leash," Dr. McKenna said. "But until it happens, I have to be cautious. I feel it's important for us to have a division between what might be out there and what actually is."
Still, strange new mammals have turned up before, he said. Twenty-five years ago another South American researcher discovered the Roman-nosed peccary in Paraguay after hearing natives talk about a third type of peccary when only two were scientifically known.
The African okapi also was documented for the first time only at the turn of the century. And a new species of antelope was discovered recently in Vietnam.