A giant panda named Lun Lun has given birth at Zoo Atlanta to two cubs, the first twin pandas born in the United States since 1987. The zoo released a video of the mother and the tiny hairless babies in their enclosure. The twins were a surprise to zoo staff who had been expecting one cub. While pandas often give birth to twins in the wild, they are only able to raise one at a time - leaving the second twin to perish. But in a zoo setting, staff are able to incubate one cub while the mother takes care of the other, and then swap them out so she can have a chance at successfully raising both.