For Release: September 15, 2004
Peper Long (202) 673-0209
Zoo Confirms Panda Pseudopregnancy
The National Zoo's giant panda Mei Xiang is not pregnant.
Zoo scientists confirmed her pseudopregnancy today, after weeks of hormonal analysis, ultrasound examinations and behavior monitoring.
On May 2, after the giant panda pair did not successfully mate, Zoo staff vaginally inseminated Mei Xiang, using a previously frozen sample of Tian Tian's semen. Vaginal insemination is different from other methods of artificial insemination. For example, uterine insemination deposits sperm directly into the animal's uterus—a non-surgical procedure that requires anesthesia. This vaginal insemination required no anesthesia, but used significantly less sperm than other methods of artificial insemination, and Zoo researchers thought it less likely to produce a cub.
Female giant pandas always undergo pseudopregnancies when they ovulate but fail to conceive. During a pseudopregnancy, hormonal changes and behaviors are identical to a true pregnancy, which makes it very difficult to determine if a panda is pregnant. Weekly ultrasound examinations did not confirm the presence of a cub but did yield what could be important data on the physiological changes associated with giant panda pseudopregnancies.
On September 5, Mei Xiang's level of urinary progesterone (a hormone associated with pregnancy) began to decline. Upon reaching a normal baseline level, this decline would end in either a cub birth or an end of a pseudopregnancy. Based on this information, Zoo researchers have determined that Mei Xiang experienced a pseudopregnancy.
Female giant pandas ovulate once a year, in the spring, and give birth between 90 and 180 days after mating. This wide gestation range is due to a reproductive phenomenon known as delayed implantation, or the delay from when conception occurs until implantation in the uterine wall.
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