Despite Romance, No New Panda Cub
Thursday, August 14, 2008
The timing is right. Both parties are interested. There's even the proper pillow talk. The problem, according to panda breeding experts at the National Zoo, is one of "alignment."
And when the zoo's giant pandas fail to mate naturally, as they did this year because they're not sure how, the zoo must resort to artificial insemination, which works only about half the time.
As a result, disappointed zoo officials said yesterday, their female panda, Mei Xiang, will not have a cub this year.
It was the second time in two years that the zoo's efforts to produce a cub failed, and the announcement ended a tense two weeks in which there were signs that the outcome might be different.
Zoo officials said yesterday that although the panda showed signs that she might be pregnant, they were not sure whether she conceived. Pandas can exhibit all the signs of pregnancy without becoming pregnant -- a pseudo-pregnancy, they said. But the panda might have conceived, and the embryo might never have developed.
The science of giant panda reproduction is complicated, and the alignment problem has cropped up before. Steven L. Montfort, the zoo's associate director for conservation and science, said the zoo will try again next year. Giant pandas generally ovulate once a year.
"People have just worked so hard and so well together here to make everything possible go right," Montfort said at the zoo yesterday. "We feel like we did everything we possibly could. Obviously, we're very disappointed. It's a terrible letdown, as you wait and you wait and you wait."
Till the end, there were strong behavioral signals that a birth might be imminent, he said, "but it wasn't to be."
Giant pandas, native to China, are endangered. There are only about 1,600 in the wild and slightly more than 200 in captivity. Panda reproduction in captivity has been problematic despite the zoo's big success in 2005, when Mei Xiang gave birth to Tai Shan.
The 230-pound Mei Xiang was artificially inseminated at 2:45 p.m. March 19 with sperm from the zoo's adult male panda, Tian Tian, who fathered Tai Shan. And as in previous years, over the succeeding months, Mei Xiang began exhibiting prenatal behaviors.
But zoo officials urged caution, saying that panda pregnancies, and those in all bears, are difficult to predict.
After ovulating, a panda almost always undergoes changes associated with a pregnancy in case she conceives, zoo experts said. Even when there is conception, a panda embryo might "float" for a time before implanting in the uterus or be reabsorbed into the panda's body and disappear. The zoo said there were some changes in the panda's uterus that could have indicated a pregnancy, but ultrasound tests never showed a fetus.