The National Zoo's giant panda Mei Xiang gave birth to a cub Sunday night. Zoo staff report they can hear the cub, but have not seen it yet. They say the sounds indicate the cub is healthy. "We are thrilled that Mei Xiang had a successful pregnancy since 2005," said Dennis Kelly, director at the Smithsonian's National Zoo, in a press release. "I'm cautiously optimistic as we haven't seen the cub yet, but we know Mei is a good mother. Like everyone else, I'm glued to the Panda Cam for my first glimpse of the cub." All photos courtesy WUSA.