Animal keepers at Zoo Atlanta are sharing the burdens of motherhood with giant panda Lun Lun to help ensure that both of her recently born twins have the best shot at survival. (Watch the Zoo Atlanta Panda Cam.)

The cubs will be rotated between their mother and an incubator to make sure they are being adequately fed and nurtured.

The tiny duo were born approximately two minutes apart on Monday night at the zoo. The cubs—the genders of which have not yet been announced—are the fourth and fifth offspring for 15-year-old Lun Lun and are the first giant panda twins to be born in the U.S. since 1987. (See pictures of zoo pandas.)

While twin giant panda births have been rare in U.S. zoos, they are actually quite common: In the wild and at other zoos around the world, giant panda mothers give birth to twins about 50 percent of the time, explained Zoo Atlanta's curator of mammals, Rebecca Snyder.

However, due to the difficulty of caring for two cubs simultaneously, typically only one of the twins survives. Giant panda newborns are even more helpless than most other mammal infants because they don't open their eyes until they are about six to eight weeks old and don't move around until about three months.

"[The mothers] have to hold the cubs and position them for nursing in the first couple of weeks. Sometimes they're just not capable of getting them positioned and one of them fails," Snyder said. (See a video of a giant panda baby.)

Right now, the staff is focused on making sure the twins survive their first 72 hours, which is especially crucial for giant panda cubs.

"That doesn't mean that after 72 hours we're safe," Snyder said, "but it definitely means things are looking good if they're both doing well at that point."

Cub Swap

By swapping the cubs out every few hours, zoo staff will ensure Lun Lun is only nursing one cub at a time. The other cub will be placed in a nearby incubator until it's returned to its mother. (Also see "Picture Archive: Baby Giant Panda Su-Lin, Circa 1936.")

"If we're not able to swap them out as frequently as we want to, then we'll supplement them with a little bit of formula to make sure they're getting enough to eat," Snyder said.

The cub-rotation technique was developed by vets at China's Chengdu Zoo in the early 1990s after they noticed giant panda mothers having trouble raising both twins simultaneously.

The Zoo Atlanta staff is also helping make sure Lun Lun herself is adequately fed during this crucial time after giving birth. "We're offering her some water and food when we're alternating the cubs, so she did have some water yesterday after she gave birth," Snyder said. (Read about the costs of housing giant pandas in zoos.)

It's not uncommon for giant panda mothers to go days or even weeks without eating or drinking as they nurse.

"Unlike a puppy or a kitten, the cub is not moving around. [Lun Lun] can't lay on her side and just have the cub come up and find a place to nurse," Snyder said. "She has to cradle it for that to happen ... [and] she'll just hold the cub the whole time."