Scientists at the Smithsonian’s National Zoo detected the start of the decline in urinary progestin levels in the Zoo’s female giant panda Mei Xiang (may-SHONG). This hormone decline indicates that Mei Xiang’s reproductive cycle will be concluding fairly soon. Animal keepers report that she has been spending more time in her den and cradles objects as she would a cub. Staff do not know whether Mei Xiang is pregnant or experiencing a pseudopregnancy, or false pregnancy, which is common in giant pandas.
Since May 2, Zoo volunteers have been monitoring Mei Xiang on the panda cam 24 hours. The Panda House is closed until further notice. Visitors may view the Zoo’s two male pandas outside from early morning until 3 p.m. daily.
Zoo scientists artificially inseminated Mei Xiang with semen from the Zoo’s male giant panda Tian Tian (t-YEN t-YEN) Jan. 17 after they determined that she had come into heat three months earlier than usual.
Since the artificial insemination, scientists have conducted weekly and biweekly hormonal analyses on daily urine samples from Mei Xiang. Zoo veterinarians are conducting biweekly ultrasounds on Mei Xiang to monitor any changes in her reproductive tract and look for evidence of a fetus. So far, they have not seen evidence of one. Panda fetuses do not start developing until the last weeks of a gestation period. Again, Zoo veterinarians stress that it is still too early to determine if Mei Xiang is actually pregnant or experiencing a pseudopregnancy. In 2005, in the last weeks leading up to the birth of Mei Xiang’s only cub Tai Shan, she would not cooperate for her weekly ultrasounds, and it was not possible to definitively determine if she was pregnant.
There is no conclusive study that indicates what causes panda ovulation. Although scientists know that giant pandas mostly breed in late winter to early spring, it is not known if the onset of reproductive activity is triggered by increasing day length, temperature or some other environmental factor. This year’s unusually early onset of reproductive activity should allow Zoo scientists to shed new light on what triggers the reproduction in this endangered species.
This is the eighth year the National Zoo has tried to breed the giant pandas. Mei Xiang gave birth to Tai Shan in 2005. Mei Xiang, 10 years old; Tian Tian, 11 years old; and Tai Shan, 3 years old, live at the Fujifilm Giant Panda Habitat at the National Zoo.
On Friday, May 1, Tai Shan underwent a physical and colonoscopy. On Saturday morning, veterinarians and animal keepers confirmed that he ate his entire breakfast meal, went into his exhibit yard to eat bamboo shoots and promptly fell asleep. He has made a full and complete recovery from Friday’s procedure.
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