National Zoo’s Giant Panda Is Not Pregnant

Staff at Smithsonian’s National Zoo confirmed today that female giant panda Mei Xiang(may-SHONG) is not pregnant but was experiencing a pseudo, or false, pregnancy during the past several months.

National Zoo scientists, veterinarians and keepers were keeping a close eye on Mei Xiang, monitoring her hormone levels and behavior, as well as conducting weekly ultrasound exams in an attempt to determine if she was pregnant. On April 20, Mei Xiang’s level of urinary progesterone (a hormone associated with pregnancy) began to decline. Upon reaching normal baseline levels, this decline would end in either the birth of a cub or the end of a pseudopregnancy. Based on this information, and not having seen a fetus during the ultrasound exams, Zoo researchers have determined that Mei Xiang experienced a pseudopregnancy.

Female giant pandas almost always undergo a pseudopregnancy when they ovulate but fail to conceive. During a pseudopregnancy, hormonal changes and behaviors are identical to those of a true pregnancy, making it very difficult to determine if a giant panda is actually pregnant or not. This is the fifth time Mei Xiang has had a pseudopregnancy. She had her only cub, Tai Shan, in 2005. Giant pandas ovulate once a year—Zoo scientists will determine whether Mei Xiang should be considered for breeding again in 2010.

National Zoo staff expect Mei Xiang to return to normal, hormonally and behaviorally, in the coming days, which includes an increase in appetite and activity level. The Fujifilm Giant Panda House will also reopen today. It had been closed to provide Mei Xiang with a quiet environment in the event that she did give birth.

Yesterday, veterinarians anesthetized male giant panda Tian Tian (t-YEN t-YEN) for scientists to collect semen to freeze and store as part of the Zoo’s collaboration with the worldwide giant panda breeding program. Giant panda semen production peaks in April and May. Giant pandas are critically endangered; scientists estimate there are around 1,600 remaining in the wild.

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SI-232-2009