Baby watch for one of the most watched females in Washington has begun.

The National Zoo said its female giant panda, Mei Xiang, was artificially inseminated Thursday. Now experts at the zoo will closely monitor her, as they wait three to six months to know whether she’ll bear a cub.

Getting a panda pregnant isn’t easy.

For starters, giant pandas are in estrus for only 24 to 72 hours each year. Because the window is so short, zookeepers have to be ready. Plus, they often have false pregnancies, triggering elation but then disappointment among panda watchers.

Officials said zookeepers had been monitoring Mei Xiang’s behavior and hormones since mid-March and noticed she was “entering her breeding season.” Hormone reports showed her estrogen levels peaked Wednesday evening — a sign that she was ovulating.

Mei Xiang had been acting as a panda that’s ready to breed does: getting restless, vocalizing, playing in water, wandering her yard and marking her scent. As a female panda is about to reach peak estrus, experts said, these behaviors increase in frequency.


Pierre Comizzoli, right, a reproductive physiologist at the Smithsonian Conservation Biology Institute, and Don Neiffer, chief veterinarian at the National Zoo, prepare for artificial insemination on giant panda Mei Xiang on Friday. (Roshan Patel/ National Zoo)

Her keepers noticed, as did the zoo’s adult male panda, Tian Tian. He “vocalized to her and constantly tried to keep her in his sight for the past week,” according to a statement from the zoo. Over the past few days, he spent most of his days at the “howdy window” that separates their two yards. But Mei Xiang played hard to get and didn’t “respond positively” to his courting.

“Every giant panda breeding season is slightly different, but Mei Xiang and Tian Tian have been displaying very clear and strong behaviors this year,” said Steven Monfort, the zoo’s director. He said the pair made it “extremely obvious to us that they were preparing for breeding.”

Mei Xiang was inseminated using semen from Tian Tian. Now it’s time, as Monfort said, “to wait and see.”


Mei Xiang has a bit of bamboo. (Skip Brown/National Zoo)

The zoo’s panda team said they won’t know for several months whether the insemination worked. The anticipation could lead to disappointment: Over the past two years, Mei Xiang has experienced false pregnancies.

Ultrasounds will track Mei Xiang over the next three to six months. A female panda may act as if she’s pregnant: nesting, eating less and not liking noise. So experts said they won’t know for sure whether she’s pregnant until they see a developing fetus on an ultrasound. But even this isn’t easy: Giant pandas are only about the size of a stick of butter at birth.

Mei Xiang will be 21 this summer and is getting close, experts said, to the end of her reproductive life cycle, though they’ve said it is still possible for her to get pregnant.

She has given birth to three surviving cubs: Tai Shan, Bao Bao and Bei Bei. Two of her panda cubs — Tai Shan, who was born in 2005, and Bao Bao, who was born in 2013, went to China last year. Bei Bei, who was born in August 2015, is set to move to China by the time he turns 4.

China, home to giant pandas, leases the animals to zoos around the globe. Giant pandas are listed as “vulnerable” by the International Union for Conservation of Nature. Experts said there are about 500 in captivity and about 1,800 in the wild.