For National Zoo's panda Mei Xiang, pregnancy proves elusive
Thursday, April 29, 2010
As early as Monday, the signs were not looking good. The National Zoo's female giant panda, Mei Xiang, was exhibiting some behaviors of pregnancy, but not all of them. The ultrasound scans of her uterus were inconclusive. And the level of certain hormones in her body were saying that her annual pregnancy cycle was over.
Plus, there was no cub.
The zoo announced Wednesday that, taking all factors into consideration, their panda was once again not pregnant.
The conclusion was reached, the zoo said, after experts studied the array of physical, behavioral and chemical clues.
"Based on current hormone analyses, and not having seen a fetus during the ultrasound exams, Zoo researchers have determined that Mei Xiang experienced a pseudopregnancy," the zoo said in a statement.
The zoo had placed the panda on 24-hour pregnancy watch Friday, and officials had high hopes that Mei Xiang might be pregnant. She was artificially inseminated twice in January. "There's still a smidge of hope," zoo spokeswoman Pamela Baker-Masson said Tuesday.
But zoo scientists realized later that Mei Xiang was not pregnant, the announcement said.
"This is very disappointing news, as you can imagine," Janine L. Brown, head of the zoo's endocrinology lab, said in an e-mail.
"Everyone puts their heart and soul into the reproductive management of these and other species," she said. "We had no reason to believe Mei's last artificial insemination would not be successful, but as so often happens, nature had other ideas."
The chief clue this week was the level of the hormone progesterone, which rises during the bear's pregnancy cycle then falls steeply back to "baseline." Once it falls back to baseline and stays there, scientists expect to see the birth of a cub within a day or so. If there is no cub, the pregnancy is declared over.
Mei Xiang's hormone levels dropped to baseline late last week. Pandas go through a pregnancy cycle whether or not they are actually pregnant.
The disappointment comes after the departure in February of the zoo's giant panda favorite, Tai Shan, who was born there in 2005. Tai Shan was sent to join a breeding program in China. In addition, the zoo faces the possibility that Mei Xiang and her mate, Tian Tian, may also soon depart.
The adult giant pandas are here on a 10-year lease from China that expires in December.
Mei Xiang has had numerous pseudo-pregnancies in the past and in a decade has produced one cub, Tai Shan.
"After all the months of hard work, it comes to nothing again," said Don Moore, the zoo's assistant director for animal care science. "The mood's kind of somber."