In one of Asia's most isolated jungles — the Foja Mountains of western New Guinea — naturalists have discovered a vast unexplored preserve of exotic species new to science.

During a 15-day expedition in December, the researchers found hundreds of rare birds, more than 20 new species of frogs, five kinds of previously unknown palms, four new breeds of butterfly, and giant rhododendrons with white blossoms the size of bread plates — believed to be the largest on record.

All told, the 3,700 square miles of mist-shrouded tropical forest may be the most pristine natural area in Asia and the Pacific, Conservation International announced in Indonesia yesterday.

"It is as close to the Garden of Eden as you're going to find on Earth," said expedition chief scientist Bruce Beehler.

Under the forest's lush canopy, animals hunted to extinction elsewhere were so plentiful and unused to human contact that they approached the naturalists unafraid, allowing themselves to be handled easily and photographed.

Blazing trails with pink and yellow flagging tape, the field team spotted 40 rare species of mammals, including six kinds of kangaroo. They also encountered a bizarre spined, egg-laying, hedgehog-like mammal called the long-beaked echidna so docile that the scientists picked up a pair and carried them back to camp for study.

It was a journey that had taken a decade of planning.

"The politics and the environmental constraints of western New Guinea are changing all the time," Beehler said. "It is difficult to get permits. By some miracle, everything came together."

The expedition was organized by Conservation International in Washington, D.C., and the Biology Research Center of the Indonesian Institute of Science.

The researchers received financial support from the Swift Foundation, the Gordon and Betty Moore Foundation, the National Geographic Society and the Global Environment Project Institute.

The custodians of the forest, which has been designated a national wildlife sanctuary, are the local Kwerba and Papasena tribes. But they rarely venture any deeper into the wilderness than its fringes, where wallabies, giant crowned pigeons, wild boar and cassowaries are abundant.

By the expedition's best estimate, more than 300,000 hectares of the old growth tropical forest have never been visited by humans.