Panpan, the world's oldest male panda, is seen at the China Conservation and Research Center in Dujiangyan, Southwest China's Sichuan province, on July 15, 2016. Wild pandas can live 15 years on average and captive ones 22 years. Like human beings, giant pandas also face growing risks of diseases, including cancer, dysfunction in digestive tract and decaying teeth, with growing age. [Photo/Xinhua]