Since 1953 when the first living giant panda was discovered and rescued in Chengdu, Sichuan Province, China has embarked on a difficult road to preserve this endangered roly-poly icon.

The Chengdu Panda Base established in 1987 has expanded from six giant pandas, all rescued from the wild, to 111 today - all bred in captivity. The total number of captive-bred giant pandas in China is 328, according to experts from the Chengdu Research Base of Giant Panda Breeding. The number in the wild is not known, though estimates range from 1,600 to 2,000 or more.

None has been successfully reintroduced to the wild. Ten attempts in the early 1980s failed.

But one "wilded" giant panda named Taotao is expected to be released into the wild soon, according to an announcement early this month from the Sichuan Provincial Forestry Bureau. He is to be released into the Liziping Nature Reserve in Simian County, Sichuan Province. A date has not been set yet.

Taotao, 26 months old, was born in a "training field" for wilding in Sichuan's Wolong Nature Reserve. He is now in a second enclosure that simulates the wild.

Six other young captive-bred pandas are in the first stages of training in a "semi-wild" preserve. They are not ready yet to go it alone. They are considered strong enough to fend for themselves and young enough to learn and adapt.

"To return the pandas safely to the wild is our ultimate goal," says Dr Zhang Zhihe, director of the Chengdu Panda Base, who recently visited Shanghai to launch a global search for three international panda ambassadors or Pambassadors.

"Our hope is to make sure they can survive the wild," he says.

Since his birth more than two years ago, Taotao has never seen a "human being," as all staff in the nature reserve area always wear panda costumes. He is with his mother. There is no more human intervention, such as feeding or regular surveillance, but if the panda is seriously ill, researchers will intervene.

Today Taotao is not only able to move about, climb trees and look for food, but he also has developed a sense of alertness and ability to avoid enemies, primarily human poachers. Because of its size, the panda has few natural enemies, but it must watch out for takin, very large goat-antelopes that can injure by kicking.

In other wild areas at higher elevations, predators include wolves, Asian golden cats, jackals and yellow-throated martens - leopards and martens can seize baby pandas. But pandas are big, with strong jaws and teeth and can fight back.

Pandas, which live on low-nutrient bamboo, have low metabolism and are not very active. They are basically docile and live companionably with other animals, such as goats, pheasants and small creatures.

"To return them safely to the wild is a slow and long process. It's really hard to say how long it will take. It could be 10 years; it could be 50 years or longer," director Zhang says.

To be successfully released, not only must a wilded panda fend for itself, integrate into the wild and coexist with other wild animal groups, but it must also breed.

"Most important is that it be able to reproduce in the wild," Zhang says.

Since the early 1980s, China has made around 10 attempts to return giant pandas to the wild, but all failed.

Giant panda Beibei was released into the wild in 1984 but found its way back to and died two months later.

Sanshan lost 25kg during four months in the wild and found its way back to the base at last in 1991. Xiangxiang was found dead after a fight with wild pandas in 2006.

The biggest problem was lack of survival skills and dependence on regular feeding.

"To protect giant pandas does not mean keeping them in an artificial environment in the care of human beings," Zhang says. "Real protection means they can live free and be strong in the wild world."

With the increasingly density of captive-bred giant pandas at the base - and the increasing risk of cross infection among them - it's essential to return them to nature. Some will be gradually reintroduced after wilding training.

"To return some to the wild gradually at the proper time can not only increase the number of healthy pandas, but also strengthen their ability to adapt to a changing environment, unpredictable, random events and improve genetic structure and diversity," Zhang says.

In 2010, construction began on a wilding training area that simulates the wild. The first phase was completed in January and the first group of six young giant pandas were moved to the base for survival training and research on pandas in the wild.

The entire Dujiangyan Giant Panda Wild Conservation Base and Research Center is expected to be completed by 2020. It will cover 1.4 square kilometers and be home to 30 to 40 giant pandas and 50 to 100 panda cubs, as well as companion animals such as goats and pheasant.

The six pandas - two males and four females - aged from 2 to 5 years, will learn how to find food - bamboo shoots. Then they must learn to strip off the leaves and shoots and eat them. Pandas have been known to eat other vegetation and they are genetically carnivores, with a carnivore's digestive system, despite their bamboo preference,

They must learn how to build secure nests with natural materials in the area, avoid enemies and many other skills.

Each panda has a GPS tag on its neck and researchers will monitor them and using GPS.

Human contact will be reduced and finally eliminated. Caretakers are not allowed to feed the pandas; refined fodder enriched with vitamins will be gradually reduced until the pandas live entirely on bamboo. The terrain has been planted in advance with different varieties of bamboo, so that some bamboo is always green.

After these first six master the basic wild living skills, the pandas will move to a larger wildness-training zone that perfectly simulates the wild environment and does not contain any manmade structures. They will be on their own, moving around and foraging.

Researchers will record their rest times and meal times; blood and feces will be collected and tested to determine their physical condition. Pandas will be observed to see whether they develop typical wild behavior or behave abnormally.

"But we have to admit that this project of returning the captive-bred giant pandas to the wild is still in the infant stage and may have risks," director Zhang says. "We have made emergency plans and if necessary there will be human intervention."

Over the past nine months, the six pandas have adapted well to the new environment and are growing healthy. Soon they will be ready for further wilding training, Zhang says.

The Chengdu Panda Base is the world's largest captive-bred giant panda base and has raised five panda generations. Since it was established in 1987 with six wild pandas, which were sick or wounded and rescued from the wild, it has not accepted any more wild pandas. Introduction of new pandas could also introduce many infections from the wild.

However, since pandas have been removed from their natural habitat for more than two decades, it remains to be seen if some can be reintroduced into the wild and survive.

"We've spent 50 years rescuing this endangered animal and we hope we can return them to the wild in another 50 years or less," director Zhang says. "The main driving force to save the giant panda, an species that dates back more than eight million years, is you, me and everyone."