It's a boy! The panda cub born at the San Diego Zoo last month has grown to 2.8 pounds and his mother, Bai Yun, finally left the den on Thursday, allowing veterinarians to examine the cub for the first time and reveal his gender. According to senior zoo veterinarian Geoff Pye, the cub has reached his "initial cute stage" and is "very roly poly." Its black-and-white markings are just beginning to show. The cub was Bai Yun's fifth, and her third with longtime consort Gao Gao, making the pair one of the most reproductively successful panda couples ever. In accordance with Chinese tradition, the new boy won't get a name until 100 days after its August 5 birth. Hopefully he'll have hit an "advanced cute stage" by then.