During a naturally-occurring estrous cycle in March 2015, Zoo staff performed an artificial insemination procedure following unsuccessful breeding sessions with male, Gao Gao. Since the artificial insemination procedure, veterinarians, animal care personnel from the San Diego Zoo along with scientists and researchers at the San Diego Zoo Institute for Conservation Research have been tracking her hormone levels and watching for behavioral signs of pregnancy. In addition to the hormone tracking, ultrasounds and thermal imaging were conducted to check for any fetal development. All methods used for monitoring for a possible pregnancy are providing conclusive negative results. Female giant pandas experience estrus just once a year and it only lasts for 48 to 72 hours. If Bai Yun had been pregnant, she would have been one of the oldest giant pandas to give birth. Her mother currently holds that record.