Giant panda "Yang Yang" (up) mates with giant panda "Su Shan" at the Bifengxia base of the China Conservation and Research Center for the Giant Pandas in Ya'an City, southwest China's Sichuan Province, April 14, 2016. The center captive-breeds the world's largest panda population -- 218 as of the end of 2015. Twenty-six female pandas have been selected in this year's mating plan. (Xinhua/Xue Yubin)