SCIENCE

Why We Don’t Have a Baby Panda

April 7, 2009

Here in Washington, D.C., we’re a bit obsessed with our pandas. We wait with bated breath for them to mate (which usually ends with an attempt at artificial insemination), wait more for word if Mei Xiang is pregnant (“we’re not sure” is the usual answer) and wait again for a potential birth (and are often disappointed).

An article in Sunday’s Washington Post Magazine explains why we were so disappointed last year.

On the morning of March 19, two lusting pandas were released into the outside yards. As if some hackneyed sitcom writer had thought up the scene, droves of schoolchildren on their spring break were just arriving at the zoo as Tian Tian's carnal instinct was cresting. He pursued his mate in the yard that morning with vigor. Occasionally, Mei Xiang would stop in place, allowing Tian Tian to thrust about her while he emitted high-pitched bleating sounds of a neck-hair-raising variety….

From a fenced-in view on the opposite side of the exhibit, Lisa Stevens remained stoic as she watched minutes of hapless humping turn into hours….

Only once, for a flickering moment, did it look like an actual copulatory event might occur, when Mei Xiang lifted her tail and backed up toward Tian Tian. But he happened not to be paying attention as she did this, and when he finally took notice, she had already pancaked to the ground. Undeterred, her mate proceeded to climb on her back, aiming himself at her side and then her back paw.

"He's only a foot or so off," Stevens said, trying to hide her frustration. "You just want to move him into position."

Tian Tian isn’t so great a lover, apparently, because he gets only one shot at this each year. In the wild, he would have opportunities with several female pandas, but with Mei Xiang his only mate and because she is only fertile for 48 hours or less each year, Tian Tian doesn’t get much practice. Even after several years, our pandas are like teenagers still trying to figure out each other’s bodies.

You might think, then, that the solution would be artificial insemination.

In analyzing the collected hormone data over the months that followed, Dave Kersey brought something to the staff's attention. His readings suggested that peak ovulation time might be later than expected, if only by a few hours. In December, he left Washington to become an assistant professor of reproductive physiology at Western University in Pomona, Calif. But if Kersey was on to something, he may have left the National Zoo with a breakthrough.

Even after 37 years of having pandas in the United States, we’re still not sure when peak ovulation occurs, which seems to make artificial insemination more of a hit-or-miss than a sure thing. We did get Tai Shan, though, out of all these efforts, and the zoos in San Diego and Atlanta have also had some luck. We’re not as completely hopeless at panda breeding as Tian Tian and Mei Xiang are.

What will this year bring?

The theory was put to the test in January, when Mei Xiang went into heat two months earlier than the previous year…. And so, on Jan. 15, Mei Xiang and Tian Tian engaged in their annual, ineffectual fling in the yards. Two days later, Jo Gayle Howard artificially inseminated Mei Xiang with Tian Tian's sperm. Howard performed two inseminations with anesthesia, as opposed to one, to take advantage of Kersey's discovery.

A cub could still be born this year, but as spring approached, Mei Xiang was keeping everyone guessing.

Will we get another Butterstick this year? We’ll just have to wait and see. As usual.