Officials and scientists for the Smithsonian National Zoological Park are playing a guessing game about whether the 10-year-old giant panda is pregnant or simply going through a pseudopregnancy,a common state in which pandas exhibit hormonal changes and behaviors that indicate they are pregnant when they're not.
Lisa Stevens,curator of primates and giant pandas for the zoo,said Mei Xiang will likely either deliver a cub or come to the end of a pseudopregnancy within the next few days. Scientists artificially inseminated the panda in March with semen from Tian Tian,the zoo's adult male panda.
Mei Xiang and Tian Tian had a cub,Tai Shan,in 2005. Tai Shan also lives at the National Zoo.
Stevens said scientists have been watching for signs of pregnancy by monitoring her behaviors and the progestin levels in her urine.
“She's been showing all the pregnancy behaviors: she's been nesting,she's been grooming her paws and her body,she's been sleeping,she's been slow and lethargic,” Stevens said.
Scientists have been performing ultrasounds on Mei Xiang,but ultrasounds cannot reach a panda's entire reproductive tract. Though an ultrasound can sometimes detect a cub if it is there,it often can't. So far,the ultrasounds have been inconclusive. That's in part because panda cubs weigh about 3 to 5 ounces at birth and are about the size of a stick of butter. Mei Xiang weighs 250 pounds.
Stevens said scientists wonder if Mei Xiang's continual cooperation with the ultrasounds is a sign that she may not be pregnant. The ultrasounds require the panda to move to a certain part of the room. About two weeks before she gave birth to Tai Shan,she stopped cooperating with the ultrasounds,acting withdrawn and aloof.
This year,she hasn't been behaving that way.
“We know we're coming to the end,because we're monitoring her hormone levels,” Stevens said. “Her behavior has been inconclusive and her ultrasounds have been inconclusive.”
Zoo spokesman Matt O'Lear said the speculation has kept employees busy – particularly the pandas' handlers. They've been going through a crash course in how to take care of a panda cub.
If twins are born,zookeepers will care for the rejected cub and later switch the two cubs in and out of the room with Mei Xiang so they would both bond with her.
Mei Xiang's pregnancy – or not – has kept other employees busy in different ways. Stevens said the zoo handled a lot of phone calls after the Web site's “pandacam” malfunctioned and stopped streaming video Wednesday night and Thursday morning. The Web site warns that if Mei Xiang gives birth,the pandacam will be turn off. Stevens said employees had to explain to a lot of excited panda lovers that it was a false alarm.
Though work at the zoo has been busy,it might get even busier,O'Lear said.
“When something like this happens,it has a ripple effect that affects us all in one way or another,” O'Lear said. “For most of us,that work would come after a cub is born.”
O'Lear said the panda habitat is built to hold one more panda – it has an extra room inside,and one of the outdoor yards can be split in two.
The pandas are on a 10-year loan from China and are scheduled to return in 2010.