National Zoo's giant panda Mei Xiang is artificially inseminated

They closely monitored her hormone levels, watched her behavior to make sure the time was right and set up a quiet night with a mate.

But it didn't do the trick. So on Saturday, the Smithsonian's National Zoo performed an artificial insemination on giant panda Mei Xiang.

There is only a short window of opportunity for a giant panda to breed, so scientists at the National Zoo have been trying to make the most of it. When putting Mei Xiang and male Tian Tian together overnight didn't result in breeding, the scientists decided toinseminate Mei Xiang with sperm collected from Tian Tian.

Last year, Mei Xiang gave birth to a female cub that lived only about a week.

Both giant pandas are at the zoo under a research and breeding agreement with the China Wildlife Conservation Association. They are among about 300 pandas that live in zoos and breeding centers around the world. Only about 1,600 giant pandas remain in the wild.

In an update on its website, zoo officials said they were hopeful that their efforts would be successful this year.

"We're encouraged by all the behaviors and hormonal data we've seen so far," said Dave Wildt, head of the Center for Species Survival at the Smithsonian Conservation Biology Institute.

The zoo promised to provide updates on Facebook and Twitter.