She chewed his ear, trying to wake him up. He batted her with his paw. She broke away and scratched herself with her hind leg. He sat up, yawned--and toppled over to snooze some more.

Adorable even when they sleep, two new giant pandas are a sensation at Zoo Atlanta, which is paying China $10 million over the next decade to exhibit them. When Lun Lun (she) and Yang Yang (he) arrived three weeks ago, they were greeted at the airport by an applauding crowd and escorted to their designer habitat by police motorcade. The governor stopped by to visit, and one couple drove several hundred miles to see them for a few hours at a party for $1,000 donors. The fuzzy black-and-white pair went on public display last weekend, and zoo attendance has as much as tripled since then.

"We're a small zoo, but we have big ideas, and the giant panda is the biggest idea of all," said zoo director Terry L. Maple, who helped rebuild a facility once so shabby that it lost its accreditation in the early 1980s.

On the other side of the country, pandas also are bringing joy to zoo-keepers in San Diego, where a female cub was born three months ago to another rented panda couple. But at the National Zoo, the mood is more melancholy: Hsing-Hsing, the surviving male of a pair given to the institution about 27 years ago, is dying of kidney failure. Officials there want another pair, but their request to China is stalled, partly because they have not offered as much money as other zoos.

The arrivals at Atlanta and San Diego are part of an extraordinary burst of activity in the international campaign to save the rare giant panda. Scientists in the United States and China have made several breakthroughs they hope will encourage the finicky breeders to reproduce in captivity. In the wild, Chinese authorities are cracking down on poaching, have banned logging that has reduced panda habitat and are conducting the first census of pandas in more than a decade.

Still, the survival of China's national symbol remains precarious. There are only 127 in zoos around the world and an estimated 1,000 in the rugged mountains of China. Some wonder whether American zoos, which can make major profits from panda exhibits, will be aggressive enough in pushing China to spend the millions raised in panda rental fees on the most essential wild panda preservation projects.

"We are making progress," said Ginette Hemley, vice president for species conservation of the World Wildlife Fund. "Things are getting better. But we are at a critical juncture. This is big money in conservation terms. It could easily slip in a wrong direction."

In Atlanta, the 2-year-old pandas inhabit a $7 million living space with several times more square-footage than the average American home. Edged by rocks, it has a trickling stream, pond, shady cave and wooden climbing structure. Scattered throughout are 14 video cameras connected to the Web site www.accessatlanta.com/pandas.

The pandas adapted to their new home quickly, zoo officials say. After initially scorning bamboo from Savannah, they now chow down heartily on Atlanta-grown bamboo. They roll around together, nuzzle and frolic on the grass. She is a little more high-spirited; he is more relaxed.

"The playful activities they have engaged in are a prelude to mating behavior," Maple said. "These animals look like they will be good breeders later in life."

Zoo researchers plan to study Lun-Lun and Yang-Yang to see how their diets, physical condition and behavior change as they grow from young adults to breeding-age adults. They are trading information with San Diego and, to a lesser extent, with the National Zoo.

Atlanta encouraged China to break with tradition and let Yang-Yang stay with his mother at the Chengdu Research Center, where he was born, until he was more than a year old. Captive pandas usually are taken from their mothers at six months so that the mothers will breed again soon. But senior research associate Rebecca Snyder said that the longer they stay with their mother, the more social skills they learn that could help them later--especially when it comes to breeding.

Atlanta's giant pandas won't be ready to mate for three years or so, and any cub they produce would belong to China.

"We'd like to keep them for their whole lives," Snyder said, "if we can."

Acquiring a giant panda is an enormously complicated venture. It took Atlanta 15 years, lots of money and help from former president Jimmy Carter, among others. Now, the National Zoo is engaged in similar negotiations--while facing some different obstacles.

San Diego and Atlanta raised a million dollars a year each to pay China's rental fees. The corporate donors--United Parcel Service, Coca-Cola and Turner Enterprises, among others--are emblazoned on the red lacquer door to the Atlanta exhibit. Atlanta raised its admission fee from $10 to $12 for adults to defray costs. San Diego's admission is $16 for adults.

But the tax-supported National Zoo doesn't charge admission. The Friends of the National Zoo, which already provides up to $1.5 million a year for a variety of zoo projects, has begun a capital campaign that includes raising $2.5 million to help in the panda acquisition effort. It plans to approach rich donors and offer various kinds of recognition. Still, a zoo source said, Washington does not have the deep corporate pockets that other big cities enjoy.

At this point, the National Zoo has offered China $2.5 million over 10 years, as well as hundreds of thousands of dollars in researchers' time to help Chinese scientists. In September, according to the zoo source, China made a counteroffer: $8 million over 10 years. Zoo officials don't plan to up their offer but will continue to make the argument that they are a special case.

Zhao Qingguo, the Chinese official in charge of lending pandas to other countries, said money is one problem with the National Zoo's application. Getting an application approved is a complicated, time-consuming process because of difficulties getting an import permit from the U.S. Fish and Wildlife Service and because of the, until recently, sour relations between China and the United States.

"We're waiting until Atlanta is finished before we really go think about other arrangements," Zhao said. "It has been very difficult to arrange. We used a lot of time and energy to get it done."

"The experience at San Diego and Atlanta has taught us that [panda acquisition] is not a short-term quick fix," said McKinley Hudson, the National Zoo's deputy director. "We're here for the long haul, until someone clearly and unequivocally shuts the door on us."

Xie Zhong, the chief of China's Zoo Association, said several zoos in the United States, Japan and Germany have made requests to adopt additional pandas, but she declined to say which ones. Chinese zoos also are clamoring for the furry creatures. Major cities around the country, such as Harbin, Shenyang and Changchun, have no pandas.

"With pandas, there are never enough," she said.

Public displays of pandas bring in money and adulation, and zoo officials say it also builds support for conservation efforts. A new Fish and Wildlife Service policy adopted in 1998 insists that most profits from panda exhibits go to research to save the species in China and that federal officials approve the specific projects. The agency froze new panda import permits from 1993 to 1998 because more than 30 zoos were seeking short-term rent-a-panda deals.

David Towne, director of the Seattle zoo and head of the panda action plan for the American Zoo and Aquarium Association, said he is frustrated that U.S. zoos have not banded together to share money and come up with a unified panda research agenda. Instead, he said, they have let the Chinese play one against another, with pandas going to institutions that can raise lots of money and political backing. He wants the federal government to take stronger action to counter this.

"It is really getting kind of crazy," he said. "I'm not sure it's helping the pandas."

Washington, to be sure, has competition. The Memphis zoo is said to be readying an application for a pair of pandas. And the Las Vegas-based Mandalay Resort Group, which owns hotels and is building an aquarium, is exploring the idea of importing pandas but has not decided whether to apply.

Ken Stansell, the Fish and Wildlife official in charge of panda permits, says his agency is taking a tougher stance on pandas than with almost any other animal. "We are going much beyond [just issuing permits] in trying to encourage the conservation of a species in a foreign country," he said.

Panda conservation efforts in China have picked up in recent years, according to officials and conservation groups. So has the success of breeding captive pandas. The Chinese forestry ministry and World Wildlife Fund are conducting a census of giant pandas in the wild that will update the commonly used 1,000 figure and also assess the loss of habitat--considered the most critical threat to panda survival.

A logging ban imposed last year will protect some panda habitat, but conservationists are worried that poor villagers who depend on wood-cutting for income will turn to poaching. The World Wildlife Fund's Hemley said she has heard reports that authorities have confiscated 71 panda skins this decade alone in just one province.

In the captive population, the Chinese are now able to keep more newborns alive. About half of panda births are twins, and the mother often rejects one. With advice from a San Diego zoo nutritionist on how to hand-rear the rejected animals, one reserve that had a mortality rate of 60 percent or more only lost one cub of the eight born this year.

San Diego's attempts to produce a panda cub were disappointing at first. Shi Shi, the elderly male of the pair the zoo received in 1996, was not interested, although female Bai Yun clearly was. Zoo scientists tried artificial insemination last year--no go. They tried again this year, aided by research that helped pinpoint the most fertile few hours within the female's annual three-day period in heat. A cub was born Aug. 21.

The baby won't be out in public until early next year, and she won't get a name until Dec. 1, courtesy of a Chinese tradition of waiting 100 days. But her image is being seen by tens of thousands of people thanks to the zoo's Web site, www.sandiegozoo.org.

"There is all of this new information coming in every day," said Donald G. Lindburg, research behaviorist and panda team leader at the zoo. "Each day that passes, we set a record for survival of an infant in this country."

The only previous births in this country--five of them, including one set of twins--were at the National Zoo, to Hsing-Hsing and his mate, Ling-Ling, in the 1980s. None of the cubs lived more than a few days, and Ling-Ling died in 1992.

Hsing-Hsing, one of the oldest pandas in the world, suffered a bout with cancer in 1997 and had both testicles removed. This year, he was diagnosed with terminal kidney disease. His keepers have had tentative "what-if" talks about euthanasia should his suffering exceed his quality of life, but for now he, too, is on a Web cam at www.si.edu/natzoo.

"We benefited greatly by all the experiences that they have put out in the published literature," Lindburg said of the National Zoo. "We didn't have to start out with a blank slate."

Special correspondent Mike Laris in Beijing contributed to this report.