Hua Mei, 15, enjoys a treat at the Ya'an base of the China Conservation and Research Center for the Giant Panda in 2012. Hua Mei is the first panda born overseas and returned to China. [Photo/China Daily]

Feeling at home

A cub will be quarantined for a month after it returns to the base.

"It takes two weeks for the cub to adapt to the new environment because the bamboo species that the bears eat in China are slightly different from those overseas. The temperature and humidity levels are also different," Zhang said.

A panda matures sexually from 5 to 7 years old and may get pregnant during this time.

Hua Mei, 15, is the first panda born overseas and returned to China. Born in the San Diego Zoo in the US in 1999, it returned to Wolong in 2004.

After the Wolong base was destroyed in the magnitude-8.0 Wenchuan earthquake in 2008, Hua Mei was transferred to the center's Bifengxia base in Ya'an.

Six months after Hua Mei returned home, she gave birth to twin cubs. One of the cubs is Tuan Tuan, one of the two pandas sent to Taiwan in 2008 as ties between the mainland and the island warmed, heralding the relaxing of travel and trade restrictions.

The other cub sent to Taiwan is Yuan Yuan. Together, the duo's names embody the hopes of reunification.

In 2005 and 2007, Hua Mei gave birth to twins twice. She later gave birth to three cubs - in 2009, 2010 and 2013.

"Hua Mei has given birth to nine cubs. She is considered a hero," Zhang said.

As part of preparations to return Hua Mei's latest cub to the natural environment, the center allows the year-old female bear to live with its mother until it no longer needs to be breast-fed.

"A wild panda stops breast-feeding her cub when the latter is between one and a half years and 2 years old. We used to separate cubs from their mothers when they were six or eight months because cubs can sexually mature earlier after they are not breast-fed. The purpose was to enlarge the captive panda population," Zhang said.

"Because there are enough captive pandas to prevent the extinction of the endangered species, the center is preparing for cubs to be released to the wild to enlarge the wild panda population. Hua Mei's cub will enjoy her milk as long as a wild cub does because the center is preparing for her release into the wild," he said.

About 1,600 giant pandas live in the wild in China, mostly in Sichuan and the northwestern provinces of Shaanxi and Gansu. Another 376 are in captive-breeding programs.

Pandas do not breed well outside their natural habitats and not all the nine pandas aged 4 to 15 have been sexually active.

"As Tai Shan has never mated, researchers have collected and frozen his sperm to apply artificial insemination to a suitable female panda," said Wang Chuandong, head of the center's animal hospital.

Mei Sheng, 11, was born in the San Diego Zoo. The male bear is the only panda in the world whose name has two meanings in Chinese - "born in the US", and "beautiful life".