National Zoo's panda -- not pregnant

The National Zoo announced Wednesday morning that its female giant panda, Mei Xiang, is not pregnant.

The conclusion was reached, the zoo said, after experts studied an 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 issued about 9:30 a.m.

The zoo had placed the panda on 24-hour pregnancy watch on Friday, and officials had high hopes that Mei might be pregnant. She was artificially inseminated twice in January. Although indications were trending against pregnancy, zoo officials still held out hope Tuesday.

“There’s still a smidge of hope,” zoo spokeswoman Pamela Baker-Masson said Tuesday.

But zoo scientists realized later Tuesday that Mei was not pregnant, the announcement said.
The chief clue 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’s hormone levels dropped to baseline late last week, and when no cub appeared, the zoo realized she was not pregnant. Pandas go through a pregnancy cycle whether or not they are actually pregnant.

The disappointment comes in the wake of the departure in February of the zoo’s giant panda favorite, Tai Shan, who was born at the zoo in 2005. Tai 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.

Baker-Masson, the zoo spokeswoman, said: "We're hugely disappointed. It's a very significant, collaborative effort...My colleagues go through herculean efforts when it comes to panda reproduction, so it's very puzzling and extremely disappointing that we didn't have a cub this year."

The adult giant pandas are here on a 10-year lease from China that expires in December.

Mei Xiang has had numerous pseudopregnancies in the past, and in ten years has produced one cub, Tai Shan.

“It’s a disappointment for all of us,” said zoo reproduction physiologist Pierre Comizzoli. “We are obviously disappointed. But we just keep trying.”

-- Michael E. Ruane