Giant pandas Yi Bao and Jin Xin are the first pair to mate naturally at the Bifengxia Panda Base in Ya’an City this year, according to officials at the base. Vice-director Luo Bo said that it takes a long time for pandas to mate, but good progress has been made this year with another panda pair also mating successfully. Female pandas are only fertile for up to 36 hours in the spring every year, so the window of opportunity is very short. Credit: YouTube/iPanda Channel