CHENGDU, July 6 (Xinhuanet) -- Giant panda Ying Ying has given birth to a set of twins, the first pair this year, in the China Wolong Giant Panda Protection and Research Center, southwest China's Sichuan Province, sources with the center announced here Tuesday.

    Although the delivery on Sunday at the Sichuan center took 13 hours, both mother and the cubs were doing well, said Huang Yan, an engineer with the center.

    One of the two cubs, weighing 141 grams, was taken away from the mother, as pandas usually only nurture one of their two cubs. Experts will initially hand rear the cub before returning it to Ying Ying's care. In this way, both of the cubs can be well nursedby their mother, experts with the center said.

    Previously, Ying Ying gave birth to eight cubs.

    A female panda normally becomes sexually mature at four to fiveyears old. They only get pregnant once a year, giving birth to oneor two cubs at a time. Panda gestation lasts 83 to 181 days. As pandas mate only in three or four days between March and May each year, they have a relatively low fertility rate.

    At the end of last year, 163 giant pandas were raised in captivity throughout China with more than half of them living at the Wolong center.

    The number of wild pandas in China is more than 1,590, while another 160 are kept in captivity worldwide.

    The Wolong Nature Reserve, founded in 1963, is the largest panda protection zone in China. Covering 200,000 hectares, the nature reserve is world-renowned as the home for pandas. Enditem