There Xiang Xiang learned to build a den and mark his territory. Zhang says the animal also started becoming aggressive toward humans, howling and biting just as a wild panda would.
"This is the first time a captive-bred panda has been trained and released into the wild," said Marc Brody, a panda conservationist and National Geographic Conservation Trust grantee.
Brody is the founder of the consulting group U.S.-China Environmental Fund (USCEF), which is working with Chinese researchers to conserve wild pandas and their habitat in the Wolong Nature Reserve and the surrounding area.
"Xiang Xiang spent two years on a hillside above the Panda Center developing [his] wild behaviors," Brody said.
He says the animal's handlers quickly noticed a change in his behavior. Instead of having docile eyes, he would look at the keepers and stare them down.
A marked improvement in Xiang Xiang's vitality and general health was also noted.
Brody says the panda was released in the western end of the Wolong Nature Reserve, a mountainous region covering 770 square miles (1,994 square kilometers) with a hundred peaks more than 16,400 feet (5,000 meters) high.
"It's an area that's known to be frequented by other pandas," Brody said. "One doesn't know whether a dominant male in the area is going to come down and kick [Xiang Xiang's] ass or not."
"This is a test case," he added.
If Xiang Xiang's release proves a success, other captive-bred panda releases may follow.
"In the future, instead of having a single training ground, we may have eight or ten," Brody said. "We might get to a point in a few years where we are releasing 15-plus pandas a year."
Such releases could help boost the genetic diversity of the wild panda breeding pool, conservationists say.
"Due to habitat fragmentation and smaller panda populations, [conservationists] are concerned about the lack of genetic diversity in pandas in the wild," Brody said.
Brody says a reintroduction program may also help return giant pandas to their former range.
Supported by funding from the National Geographic Society, USCEF and research institutes are working to identify potential new giant panda habitat in the Sichuan Giant Panda Sanctuary.
(Related news: "Pandas' Natural Habitat Must Expand, Experts Warn.")
This 3,700-square-mile (9,583-square-kilometer) area surrounding the Wolong Nature Reserve has the largest contiguous block of giant panda habitat in the world.
"We hope to map and monitor pretty much all of the sanctuary," Brody added.
Researchers would then calculate the optimum panda population for the region, using captive-bred pandas to increase numbers where needed.
"You have this large area of potential habitat which is not fully utilized by pandas," Brody said.
"We're going to try to improve and restore habitat, create corridors to link panda populations, and then, where possible, we'll be able to repopulate those areas.
"We may be able to approximately double the wild panda population," he said.
However, Brody says, the longer term question isn't, Can we train a panda to be released into the wild?, but, Is there going to be a wild for the panda to live in?
Road building and development fueled by panda tourism and China's fast-growing economy pose the major threat to giant pandas, says the World Wildlife Fund (WWF). The international conservation group has the famous black-and-white creature as its symbol.
"Even if captive-bred pandas are successfully released into the wild, WWF does not believe that captive breeding alone is an effective conservation method to save giant pandas," said Dermot O'Gorman, WWF China's country representative.
"Protecting the pandas' habitat is the most important step in giant panda conservation," he said.
Free Email News Updates
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
SOURCES AND RELATED WEB SITES