Seven-year-old giant panda Kelin gives birth to twin female cubs at the Chengdu Research Base of Giant Panda Breeding in Southwest China’s Sichuan province, June 22, 2015. The tiny cubs are the first set of twin giant pandas to be born this year. In 2013, Kelin reached a state of sexual arousal but refused natural sex. Researchers had to show her a video of pandas mating. (Photo provided by Chengdu Research Base of Giant
