Scientists and veterinarians at the Smithsonian's National Zoo and Conservation Biology Institute are playing a game of chance.
On Thursday, they artificially inseminated a giant panda named Mei Xiang. Like all female giant pandas, she is only in estrus — able to get pregnant — for 24 to 72 hours each year.
Those aren't great odds, but Mei Xiang and her panda sperm donor, Tian Tian, are being carefully monitored. Her keepers first noticed she might be heading into her breeding season earlier this month when she started getting restless, pacing her enclosure and playing around in the water.
Tian Tian noticed, too. He started vocalizing in response, and always tried to keep his beau in sight by spending most of his time at a window that separates his yard from hers.
When the reproductive support team saw the two pandas' behavior change, they knew it was go-time.
"They made it extremely obvious to us that they were preparing for breeding," said Steven Monfort, the John and Adrienne Mars director of the Smithsonian's National Zoo and Conservation Biology Institute, in a press release on Thursday. "In turn we have been tracking Mei Xiang's hormones to make sure we didn't miss the optimal window for an artificial insemination."
Now, they wait.
"It's time to wait and see if we were successful," said Monfort. But it may take several months before they have an answer.
The problem is, the only way to tell if a giant panda is pregnant is to use ultrasound to see a growing fetus. Hormone testing alone won't work; the 20-year-old panda's hormones could mimic pregnancy, even if she has a false pregnancy, which has happened before.
If the pregnancy is successful, Mei Xiang will give birth to her fourth surviving cub, The Washington Post reports.
The zoo's research was approved by the China Wildlife Conservation Association and the U.S. Fish and Wildlife Service. Giant pandas, previously considered endangered, were downgraded to "vulnerable" by the International Union for Conservation of Nature in 2016.
Fans of the "it couple" can check the zoo's Twitter account for updates on the pregnancy, using the hashtag #PandaStory. Or they can try following Mei Xiang's personal account. But fans beware; her bio says she isn't associated with the Smithsonian's National Zoo and she isn't Twitter verified.