WASHINGTON, D.C.: A rare giant panda called Mei Xiang gave birth to twin cubs at the Smithsonian National Zoo in Washington on Saturday, apparently surprising delighted zoo officials who had expected just one baby. A first tiny cub—pink, hairless and only about the size of an adult mouse—was born at 5:35 pm (2135 GMT) and Mei Xiang reacted by tenderly picking up the cub. Pandas are famously challenging to breed in captivity, but just when conservationists thought they had heard all the good news, the zoo tweeted just a few hours later: “We can confirm a second cub was born at 10:07. It appears healthy. #PandaStory.” The birth of the twins appeared to be a surprise, as the zoo’s Twitter feed had only previously referred to the expected birth of a single cub.