ATLANTA (AP) — Surprise! Three young giant pandas born at Atlanta's zoo that were thought to be males are actually females.

Actually, it's not so surprising.

"When they're born, there's really not much external difference to note," Zoo Atlanta deputy director Dwight Lawson said, explaining why four of the five cubs born at the zoo have initially had their gender misidentified.

The zoo announced Friday that 3-year-old Po and 4-month-old twins Mei Lun and Mei Huan are females, rather than males as originally thought. Mei Lan, the first panda born at zoo Atlanta, was originally thought to be female, but was later determined to be male. Five-year-old Xi Lan is the only one whose gender was correctly identified.

Staffers from the Chengdu Research Base of Giant Panda Breeding in China examined each of Zoo Atlanta's pandas shortly after their birth and announced their gender. But mistakes are common because there are virtually no external indicators. They also have only one cub at a time — or, in the case of the twins, two of the same gender — so officials don't have a basis for comparison.

Under a deal between China and the U.S., all giant pandas originally from China are loaned to foreign zoos. They and any cubs they produce must all return to China eventually.

Xi Lan and Po are set to leave for China at some point in the next few months. It was during a pre-shipment examination that veterinarians began to suspect that Po might actually be female.

"We said enough of this, let's do the genetic testing and confirm everybody and see where we stand," Lawson said.

The DNA testing revealed Po and the twins are female. There are no plans to change their names.

The fact that the three pandas are female is actually good news, Lawson said.

"Certainly in China, they're considered of more value for increasing the population," he said.

The entire panda population in captivity is managed genetically and demographically, and if Lun Lun, the mother of all five pandas born at Zoo Atlanta, had more boys, they would have had fewer breeding opportunities, Lawson said.