Giant pandas remain an endangered species despite the births of 23 cubs in Chinese zoos over the past two months, a leading panda researcher in southwest China's Sichuan Province said Thursday.

Since the boom, the total number of giant pandas in captivity at zoos worldwide had topped 300, a target Chinese scientists set in 2002, said Zhang.

"It's good news, but the number is still not big enough for the bears to be taken off the endangered list," said Zhang.

China's panda experts believe the 300 pandas in captivity are the minimum viable population for the species to reproduce and sustain in 100 years to come.

To achieve that goal, Zhang and his colleagues have worked to expand the panda population by helping the sex-shy animal breed since the Chengdu base was founded in 1989.

"The growth in the number of artificially-bred pandas, however, was inevitably accompanied by a decline in the quality and genetic diversity, as many captive pandas are blood relations," said Zhang. "This will hinder the species' survival in the long run."

While all the captive-bred pandas were offspring of the 46 wild pandas who were first kept in zoos, he said 61.4 percent of them were offspring of four giant pandas -- Pan Pan and Dong Dong at the Wolong China Giant Panda Protection and Research Center, and Ha Lan and Lin Nan at the Chengdu base.

Pan Pan alone had 107 offspring, said Zhang. "It's hard to avoid inbreeding when so many pandas share the same blood."

Panda researchers have therefore shifted their focus to from quantity to quality, he said. "We're no more satisfied with the mere expansion of the species. Rather, we are aiming to improve the quality of the breeding."

Zhang said Chinese zoos had been working to avoid inbreeding by swapping either pandas or their frozen sperm since 2004.

Meanwhile, wild training of zoo pandas has topped the agenda at the Chengdu base and the Wolong center, China's top two panda research bodies, in the hope the bears will eventually return to the wild.

In May, the Chengdu base began building a wild training center for captive-bred pandas at Majiagou, of Yutang Town in the city of Dujiangyan City. The 135-hectare area will host 40 to 50 giant pandas raised in captivity for wild training.

In August, a captive-bred giant panda gave birth to a male cub in a near-wild environment in forests of Wolong. Another three pregnant giant pandas are expected to delivery this year.

"The wild training is essential to improving panda's survival skills in the wild environment," said Zhang Zhihe. "If the training proves successful, it will eventually help pandas' restore their wild nature and save the species from extinction."

Under both programs in Chengdu and Wolong, pandas under training are expected to live in the wild on their own, while zoo workers will observe them through surveillance cameras.

If they need help, the workers will show up dressed in costumes that make them look like giant pandas, in order to reduce the animals' reliance on humans.

At the Wolong center, the expectant panda mothers under wild training are expected to give birth in the forest, covering some 20,000 square meters, and will live there until the young pandas are three or four years old.

The Wolong program is the second phase of a plan to gradually release captive-bred giant pandas into the wild.

The first phase of the scheme, launched in 2003, suffered a setback when Xiang Xiang, a 5-year-old male giant panda, was found dead in 2007, 10 months after he was returned to the wild. He had apparently been attacked by wild pandas.

According to Li Desheng, deputy director of the Wolong center, Xiang Xiang's case proved that wild panda communities were very reluctant to accept male outsiders.

Researchers, however, refused to be discouraged by the setback.

"The ultimate goal of panda breeding research is not to raise them in captivity, but to release them to the wild," said Zhang Zhihe.

Giant pandas are the world's most endangered species. About 1,600 live in the wild. (Xinhua)