One of the National Zoo’s giant pandas has given birth to a cub. Mei Xiang, who at 22 is the oldest panda mama in the country, started licking her body on Friday afternoon in a sign of labor. At 6:35 p.m., as so many people logged onto the zoo’s panda-cam that it crashed, the little one arrived. The zoo said on Twitter that Mei Xiang is “caring for her newborn attentively. Positive mothering behaviors include nursing her cub and cuddling it close.” Zoologists had said at her age, Mei Xiang had only a 1 percent chance of a healthy birth after she was inseminated with thawed sperm from her mate. She’s had three other cubs, all of whom were sent to China when they were 4 years old as part of an agreement with the U.S.