There is news today from the panda pregnancy watch at the National Zoo: The female, Mei Xiang, is not expecting.
The zoo's pair of giant pandas did not mate successfully this year, and Mei Xiang was given a type of artificial insemination on May 2. Zoo scientists said they did not think it would work, and officials said today that hormone tests proved that it had not.
Instead, they said Mei Xiang had a "pseudopregnancy," in which she ovulated but failed to conceive, resulting in hormone changes that resemble those during pregnancy. This is common in giant pandas, and makes it difficult to tell whether the animal truly is pregnant.
The panda had been having weekly ultrasound examinations, which showed no evidence of pregnancy. Zoo officials added an extra evening shift of volunteers this month to watch for pregnancy-related behaviors.
Mei Xiang's level of one hormone, urinary progesterone, began declining on Sept. 5, signaling either that a birth or end of false pregnancy was near, zoo officials said.
Mei Xiang and her hoped-for mate, Tian Tian, arrived from China on a 10-year loan in December 2000.
Pandas are unreliable breeders -- among other things, the female is in heat for only two days a year. The National Zoo pandas mated briefly last year, but no pregnancy resulted. They attempted to mate this year, but did not.
As their mating window closed this year, zoo scientists vaginally inseminated Mei Xiang with Tian Tian's sperm. The procedure used much less sperm than in natural mating, and is less effective than depositing sperm directly into the uterus, which would have required anesthesia. The method that they tried this year did not require anesthesia because the female panda has been trained to accept some medical procedures.