In Brazil, U.S. Scientist Thinks He’s Close to Finding Huge Sloth Thought to Be Extinct : Wildlife: Several people have reported seeing a creature more than six feet tall, weighing more than 400 pounds, in the Amazon wilderness. Skeptics say it’s a myth.

A U.S. scientist who has spent 17 years studying Amazon wildlife says he is close to discovering a giant ground sloth that is bigger than most men, stands on its hind legs and tears palm trees apart with its powerful claws.

David C. Oren, a zoologist with a doctorate from Harvard, said in a telephone interview Tuesday that in a monthlong expedition in the western Brazilian state of Acre, he found strong evidence of the sloth’s existence.

Oren plans another expedition in late May to search for what he said could be the largest mammal in the Amazon, survivor of a species thought to have become extinct thousands of years ago.

On his latest expedition, which ended last week, Oren said he talked to several people who reported seeing animals fitting the description of an extinct ground sloth: more than six feet tall, weighing more than 400 pounds, with dark or reddish fur.

Indians, rubber tappers and prospectors who live in the forest say the animal is shy but can be fierce when confronted by people, Oren said, adding: “Everyone we talked to was absolutely, utterly terrified of this animal. Where these things are reported, people don’t go anymore.”

A gold prospector told him a “giant monkey,” its upright body covered with reddish fur, charged at him in the forest. The man said he shot the beast in the face, then fainted in fear. The man led Oren’s scientific expedition back to the spot.

“He did probably hit it,” Oren said. “There was a pool of blood.” Oren and his party searched the forest around the spot but found no animal remains. They did find large, round paw prints with marks of clawed toes pointing inward, characteristics that Oren said would fit a ground sloth.

“No known mammal makes tracks like that in the Amazon,” he said, adding that he found another set of similar tracks more than 100 miles away. And he said he heard a strange, roaring sound that he believes is the creature’s call.

He heard it first in the afternoon. Then, when staying at a jungle hut two days later, he heard it again at night, “three more times, just after the moon rose.”

It was, he said, an “extremely strong” sound with a steady pitch for up to 45 seconds, “like jets flying over low.”

Oren, 40, works at Emilio Goeldi Museum of Natural History, a prestigious research institution in the city of Belem, at the mouth of the Amazon River. After he first came to the Amazon region in 1977, he began hearing tales of a large, manlike forest animal, sometimes called Mapinguari.

Skeptics label Mapinguari a mythical creature, like the Himalayan Yeti or Bigfoot of the Pacific Northwest. But the more Oren heard, the more he wondered if it might be a sloth.

At least eight different genera of ground sloths existed in the western Amazon 50,000 years ago, when the region apparently was more of a sparsely forested savannah than a jungle. Fossil remains of those animals indicate that some were bigger than today’s elephants.

The animal Oren is seeking would be the descendant of a smaller, more recent mylodontid ground sloth, generally thought to have been extinct for about 8,500 years, he said. No ground sloths are known to exist today.

Oren’s research on the possibility of living ground sloths began nine years ago. In December, Scientific American magazine published a summary of his findings and his theory that a small population of the sloths may still live deep in the sparsely populated, little explored Amazon forest of western Brazil.

He said descriptions of Mapinguari are consistent: Unlike Brazil’s small tree sloths, it can move rapidly on all fours or on its hind legs; it is clubfooted, with a large, heavy tail; its face is “monkey-like,” and it eats forest fruits and palm hearts. “Its very powerful claws twist the trees to the ground,” Oren said.

He said that on his next expedition, he has “every hope” a ground sloth will be seen and perhaps captured. “The evidence is continuing to grow and grow, and we are getting very close,” he said. “Reports in the area where we are planning on going are very, very strong.”

Guilherme Maia, director of the Goeldi Museum, told a Brazilian newspaper that Oren is a “brilliant” researcher and “would not get into this if he did not have sufficient proof that he will find the animal.”

If the expedition finds a giant ground sloth, it will prove not only the survival of a remarkable animal, long thought to be extinct, but would also serve as a dramatic example of why many scientists feel strongly that the Amazon rain forest must be preserved for study.

“The take-home message is how little we know of the biological wealth of the Amazon,” Oren said. “What else does the Amazon have that we are not aware of?”