San Diego Zoo Giant Panda Duo Pair Up for Endangered Species Conservation

     Over the weekend, female giant panda Bai Yun began to exhibit signs of estrus and was paired with male Gao Gao on Sunday and again on Monday at the San Diego Zoo. Although the pair showed interest in each other on Tuesday, it did not lead to another coupling. In 2003, 2005, 2007 and 2009, the results of this match led each time to the birth of a single cub.

     The giant panda team, made of zookeepers, veterinarians, nutritionists, scientists and others, will monitor Bai Yun's behavior over the coming months, looking for signs of a possible pregnancy. If this week's breeding attempts successfully lead to a pregnancy, it would make 20-year-old Bai Yun the oldest-known female giant panda to give birth. If this occurs, a cub could be born in late summer or fall.

     Unfortunately, the 2011 breeding season was not fruitful. Last year, San Diego Zoo Institute for Conservation Research scientists observed increases in Bai Yun's progesterone levels typical of past pregnancies, and behavioral changes, such as activity levels and suppression of appetite, at levels similar to prior gestation periods. Thermal images last year revealed activity in both the left and right uterine horns; however, ultrasound images never revealed a fetus nor was a cub born.

     Bai Yun's behavior and hormone levels did not indicate that age contributed to a failed pregnancy in the 2011 breeding season. Medical exams of Gao Gao also offer no obvious age-related issues that would prevent conception. Because both pandas are in good health and both exhibited signs of breeding interest, the panda team allowed the pair to mate this year.

     Bai Yun has delivered five cubs at the San Diego Zoo. In 1999, her first cub, Hua Mei, became the first giant panda conceived by artificial insemination in the Western Hemisphere and the first in the United States to survive to adulthood. Four of Bai Yun's offspring are now in a breeding program in the People's Republic of China. Her fifth cub, Yun Zi, remains at the San Diego Zoo.

     Bai Yun was born at the China Center for Research and Conservation of the Giant Panda in the Wolong Nature Reserve on Sept. 7, 1991. She was the first panda to be born and survive at the breeding center. Bai Yun, who's name means "white cloud" in Chinese, arrived in San Diego in September 1996 on a research loan. Gao Gao, a 20-year-old rescued, wild-born giant panda, arrived at the San Diego Zoo in January 2003 from China after reintroduction efforts failed to keep him out of areas inhabited by humans.

     The San Diego Zoo is one of four zoos in the United States with giant pandas. The Zoo began its long-term giant panda conservation partnership with the China in 1996 to study this endangered species. As part of this long-term program, the Zoo is collaborating with the Chinese Academy of Science in studies of behavior, ecology, genetics and conservation of wild pandas living in the Foping Nature Reserve.