A panda was born last night at the National Zoo in Washington, DC. It marks the third birth for Mei Xiang, a 25-year-old giant panda, who picked up and began cuddling her cub immediately after it was born. Conceiving cubs in captivity has been a continued struggle — Mei Xiang's pregnancy only came as a result of an artificial insemination back in March — and giant pandas continue to remain on the endangered species list in part because of it. As of 2004, there were only believed to be 1,600 remaining.

The pregnancy was only determined earlier this month

The National Zoo says that the newborn is doing well, and it plans to further examine the cub's health at some point today. But while the zoo has been closely monitoring Mei Xiang over the summer, it wasn't actually certain that she had become pregnant until recently: short of developing a fetus, female pandas almost always exhibit all of the symptoms of pregnancy after ovulation, in what's called a pseudopregnancy, reports LiveScience. The National Zoo says that ultrasounds are the only way to definitively determine if a pregnancy is real — but even as of Mei Xiang's most recent ultrasound, taken on August 5th, the zoo still wasn't able to tell.

Only when Mei Xiang's water broke on August 7th could the National Zoo confirm the pregnancy. The Washington Post reports that following the birth of her first cub in 2006, Mei Xiang experienced a false pregnancy during each of the next five years. A second cub was born last year, but it died just a week after birth. Among the difficulties in getting a panda to conceive is the precise timing that's required: Animal Planet reports that there's only a single 24 to 36 hour period each year that female giant pandas are fertile. Fresh and frozen semen from two separate males were used to inseminate Mei Xiang, and the National Zoo still has to determine which of the two is the father.

The birth was streamed live online over the same cameras that the National Zoo has been using to monitor Mei Xiang's health since her water broke. The zoo is encouraging viewers to post any screenshots of the newborn onto a Flickr group, which so far has collected about a dozen photos of the cub. Though the streaming cameras are expected to be down at some point today, once they're back online viewers should be able to continue watching Mei Xiang and her newborn around the clock.

Update 8/24: Two attempts were made to perform a checkup on the newborn cub today, but neither were successful, reports the Associated Press. Mei Xiang was reportedly cradling the cub, prevented zookeepers from examining it. A third attempt is now planned for Sunday.

Update 8/25: Mei Xiang gave birth to a second, stillborn cub. The National Zoo says that the cub wasn't fully formed and had never been alive. Mei Xiang reportedly groomed the second cub for 17 minutes before dropping it on the ground, where zoo staff retrieved it. The first cub appears to remain well for now, and it was said to be squealing throughout the ordeal.

The National Zoo says that giant pandas have a 50 percent chance of giving birth to an additional cub, and zookeepers had been on the lookout for a second birth throughout yesterday. However, 16 hours after the first cub was born, the zoo noted that it was "extremely unlikely" for a twin to be born at that time.