The smaller of a two twin panda cubs born on Saturday at the Smithsonian's National Zoo in Washington, D.C. has died, the zoo announced on Wednesday.
"This is a hard loss for us," zoo director Dennis Kelly said at a press conference.
"It's hard to keep these tiny creatures thriving," Kelly said.
Giant panda Mei Xiang gave birth to the twin cubs on Saturday night. Zoo officials said at the time that the cubs were vulnerable given their size, but both appeared to be healthy.
Giant pandas have twins about 50 percent of the time. In general, panda mothers have difficulty in caring for two babies at once so they leave the other cub to die.
“These cubs are very fragile,” said Don Neiffer, the zoo’s chief veterinarian.
“Pandas don’t have a great track record at trying to raise twins,” Neiffer said.
Zoo keepers tried to switch the twin cubs and place one of them in an incubator every four hours to allow Mei Xiang to nurse and bond with them one at a time.
Last night the smaller cub was with its mother and throughout the night it is reported that the baby was nursing and showing no signs of distress.
"Mei Xiang was doing everything right," said Neiffer.
However, this morning, after swapping the cubs for feeding with her mother, zoo officials discovered that the smaller cub was struggling.
"We are sad to report that the smaller of the two panda cubs has died," the zoo announced on Twitter.
The zoo said the larger cub appears to be strong, robust, and behaving normally.
No official cause of death has been revealed, but a necropsy will determine the exact cause of death, zoo officials said.
Seventeen-year-old Mei Xiang has given birth to two other surviving cubs - Tai Shan, who was born in 2005 and returned to China in 2010, and Bao Bao, who is 2.