The lungs of the 6-day-old cub were “poorly developed and likely caused her to have insufficient oxygen,” according to a necropsy.
The mortality rate for pandas in their first year in captivity is estimated to be 26 percent for males and 20 percent for females, zoo officials said.
“We are working with our colleagues in China to answer questions about giant pandas that will ensure the best care in captivity and that will help bolster the species’ numbers in the wild,” the zoo said in a statement. “The information about how this cub died will add to the scientific body of knowledge about giant pandas. The zoo will continue to work closely with its Chinese colleagues and share the information it has learned about giant panda reproduction and cub health.”
The Sept. 16 birth of the panda, which had yet to be named, made it an instant celebrity in the nation’s capital, but excitement turned to grief after the cub, about 4 ounces, died less than a week later.
The cub’s mother, Mei Xiang, is “almost completely back to her old self,” the zoo said. Mei Xiang and Tian Tian, on loan from China until 2015, are among Washington’s most popular tourist attractions.
Another cub was born at the National Zoo to the pair in 2005. That cub, Tai Shan, was sent to China in 2010.
But five cubs were born between 1983 and 1989 to a different pair of pandas — now deceased — at the zoo, and none of those lived more than a few days. Giant panda cubs are highly susceptible to infection.
Three other U.S. zoos have pandas: San Diego, Atlanta and Memphis. Only 1,600 giant pandas remain in the wild and a little more than 300 live in captivity.