Photo taken on May 4, 2017 shows giant panda Mao Er at the Chengdu Research Base of Giant Panda Breeding in Chengdu, southwest China's Sichuan Province. A pair of giant pandas, male He Xing and female Mao Er, will head to Copenhagen for collaborative research between China and Denmark. They will live in Copenhagen Zoo for 15 years, according to the agreement signed between the Chinese Association of Zoological Gardens and the zoo. (Xinhua/Xue Yubin)