1998-01-26 04:00:00 PDT SAN FRANCISCO -- There's big news today from Madagascar.

Five rare and endangered lemurs that San Francisco zoo veterinarian Graham Crawford carried from America to release into the animals' ancestral jungle are thriving happily there.

They've taken up with their wild relatives, although not without some conflict and interhemispheric sexual confusion.

They've virtually given up their lifelong American diet of monkey chow for the abundant local forest fruits.

And they've left the ground to frisk high in the canopy of their tropical nature preserve, while learning to leap from branch to branch, and surviving falls from treetops as high as 60 feet.

All that is good news indeed for Crawford's human colleagues at the San Francisco zoo, including director David Anderson who hopes more captive-bred lemurs can be successfully returned to restore Madagascar's vanishing lemur population.

Anderson chairs the Madagascar Fauna Group, an international organization of zoos dedicated to saving the world's most endangered creatures that inhabit the island nation.

The San Francisco zoo's lemurs don't have tall trees to fall from, but crews are reconstructing the primate area and building a more accurate replica of their native habitat for them. Other fauna there are the two nocturnal aye- ayes, members of the lemur family, and officials are hoping to include endangered Madagascar reptiles and turtles in the exhibit.

In a unique experimental effort to preserve Madagascar's 32 vanishing varieties of lemurs, Anderson's international group has sponsored the first "return" of five captive-born black and white ruffed lemurs from America to the

Betampona Nature Reserve, a natural habitat of the species.

The five furry little primates were born and raised at the Duke University Primate Center in North Carolina, where the wildest terrain they ever saw was their "boot camp" in a small, fenced forest on campus.

In October, Crawford caged them for the 42-hour flight to Madagascar via Paris, and once at the 6,000-acre reserve, they were released into the forest.

Amply supplied with open containers of water and trays of civilized food placed on the ground and hauled high into the trees, the immigrants quickly learned where the wild lemurs naturally live and frolic and forage.

"We all hoped they'd stay up close at first so we could watch them carefully," Crawford said in San Francisco. "But they scrambled up into the trees right away, leaping from branch to branch.

"That was a leap of faith, too, because they faced a pretty steep learning curve where if you don't make it, you die."

To zoo director Anderson, Madagascar is "the conservation hot spot" of the world, where hundreds of animal and plant species found nowhere else on Earth are threatened by the rapid destruction of their habitat.

People of the impoverished nation in the Indian Ocean off the coast of Africa have little fertile land to till, so slash-and-burn agriculture is swiftly destroying the forests to make way for rice planting that in turn quickly destroys the soil's fertility.

The government has finally created a few national parks and nature preserves where the native wildlife can be protected, Anderson said.

And plans are under way to release more captive-born animals from zoos around the world, including San Francisco's -- if the first experiment with the five lemurs Crawford took to Madagascar succeeds.

"If we don't get started right away," Anderson said, "there'll be nothing left there to save."

So far, it appears, the first experiment is proving a big success.

The lemur cast that Crawford carried to Madagascar includes Zuben'Ubi, a 12-year-old male; Praesepe, an 11-year-old female; Sarph, Praesepe's 4-year-old son; Letitia, Praesepe's 6-year-old daughter; and Janus, Letitia's 18-month-old son.

In lemur society, incidentally, it's the females who rule the roost; they're the dominant ones.

Back in San Francisco, Anderson and Crawford and Eva Sargent, the zoo's director of conservation and science, have been receiving e-mail reports from the Madagascar Fauna Group's field workers on the scene.

According to the messages, Praesepe has encountered a wild lemur named Boot. But because she lived so long in North Carolina, she and Boot can't seem to hit it off.

Praesepe has just come into estrus, the proper term for heat, but it's the wrong season for Madagascar.

Back in North Carolina, female lemurs are receptive in January, but in Madagascar, it happens in June and July. So while Praesepe is ready, Boot is confused.

He has tried half-heartedly, but he really isn't ready and probably couldn't impregnate her anyway because his hormones aren't up to it, said Dean Gibson, a Duke University zoologist.

But Boot is still eagerly following Praesepe, even though she cuffs him on the nose when he comes too close. "He must be either confused or astounded at his good luck, although it's unlikely that he is in breeding condition," the reports say.

Meanwhile, Zuben'Ubi is quite ready to impregnate Praesepe, and has been busy fighting with Boot for the privilege.

At the same time, Praesepe has been observed fighting aggressively with other wild females in the area -- "but fortunately without much damage so far, although we're wondering what will happen when Praesepe's hormones get in synch with the local season," Gibson said.

Letitia and her son Janus are accustoming themselves more slowly to their new habitat, but they, too, have made themselves at home high in the trees.

In fact, Letitia has already succeeded in protecting her youngster against attack by a Madagascar hawk. The raptor buzzed the family, startling Letitia, but on the bird's next pass she chased it away with a noisy charge, Gibson said.

The field workers at the reserve have counted about 30 wild lemurs in the forest there, and by following the five newcomers closely, they have observed them ranging more and more widely in the home territory of the forest's native Sahabefoza lemur group.

"All five of the released ruffed lemurs continue to adapt very well to forest life, spending days foraging for food and resting, just as do their wild-born counterparts," said Charles Welch in an e-mail from the Betampona headquarters.

"Now our concern is that they don't bully their . . . relatives too much. Stay tuned."