Scientists at the Smithsonian's National Zoo confirmed a secondary rise in urinary progesterone in its female giant panda Mei Xiang. The slow rise, which started around mid-July, indicates that she will experience the end of a pseudopregnancy or give birth to a cub in 40 to 55 days. Mei Xiang was artificially inseminated twice March 30 after natural breeding attempts with the Zoo's male panda, Tian Tian, were unsuccessful.
During the first procedure she was artificially inseminated with fresh as well as frozen sperm collected from Tian Tian in 2003. During the second procedure she was artificially inseminated with frozen then thawed sperm collected from Tian Tian in 2003 and frozen sperm from the San Diego Zoo's male giant panda, Gao Gao. Tang Chunxiang, chief veterinarian of the China Conservation and Research Center for the Giant Panda in Wolong, performed the artificial inseminations alongside a team of Zoo scientists, veterinarians and keepers.
Since the artificial inseminations, the Zoo's panda team has monitored Mei Xiang closely. Zoo scientists will continue to monitor her hormone levels through daily hormone analyses. Veterinarians are conducting ultrasounds regularly as Mei Xiang chooses to participate in them, to monitor changes in her reproductive tract and evaluate for evidence of a fetus. Giant panda fetuses do not start developing until the final weeks of gestation, making it difficult to definitively determine if there is a pregnancy. It may be too early to detect a fetus.
Keepers are also monitoring Mei Xiang's behavior closely. She has begun nest building, which is consistent with a rise in urinary progesterone. The area of the David M. Rubenstein Family Giant Panda Habitat closest to her den will close soon to provide quiet for Mei Xiang, who shows extra sensitivity to noise during the final weeks of a pseudopregnancy or pregnancy. Panda fans can watch Mei Xiang on the upgraded panda cams, sponsored by the Ford Motor Company Fund. The cams in Mei Xiang's den, where she will be spending much of her time for the next month, have also been replaced with high-definition cameras. Visitors to the David M. Rubenstein Family Giant Panda Habitat will see Tian Tian in his yard and inside the panda house as usual and Mei Xiang when she chooses to go into her outdoor exhibit.
Mei Xiang has given birth to two cubs, both as a result of artificial inseminations. Her only surviving cub, Tai Shan, was born as the result of an artificial insemination July 9, 2005. He now lives at the Bifengxia Panda Base in China. Her second cub, a female, was born Sept. 16, 2012. The cub died one week later as a result of lung and liver damage. The poorly developed lungs likely caused the cub to have insufficient oxygen, which was consistent with changes in the liver. Tian Tian sired both cubs.
Both pandas are at the National Zoo as part of the Giant Panda Cooperative Research and Breeding Agreement signed in 2011 by Chinese and Zoo officials. The agreement extends the Zoo's giant panda program through the end of 2015.
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