A giant panda surprised its keepers by giving birth to a stillborn cub at the Smithsonian National Zoo in Washington on Saturday evening, a day after the animal delivered a live cub, an official said.
The stillborn cub was born with "many abnormalities" and when a staff member retrieved it from the floor of its mother's den it was "very apparent it had never been alive," said zoo spokeswoman Pamela Baker-Masson.
The mother panda, 15-year-old Mei Xiang, while holding onto the firstborn cub, groomed the stillborn cub for 17 minutes before letting it down, Baker-Masson said.
"The fact that Mei never set down the first cub shows us, it demonstrates that she's a terrific mom," she said.
Giant pandas, which are one of the world's most endangered species, have their natural home in a few mountain ranges in central China. There are about 1,600 known to be living in the wild and another 300 in captivity, mostly in China.
About 50% of panda births are twins, but when midnight came and passed after the first birth, which occurred at 5:36 p.m. local time on Friday, officials at the zoo and a visiting panda expert from China believed there would be no second birth, Baker-Masson said.
But to everyone's surprise, the stillborn panda cub arrived at 7:29 p.m. local time on Saturday, she said.
The first born panda cub appears to be healthy.
A necropsy was under way on the second cub and officials at the National Zoo planned to provide more details on Sunday.