The death of a six-day-old giant panda cub at the National Zoo in Washington - an agonizing blow to wildlife conservation efforts - could be linked to an abnormal liver, the zoo's chief veterinarian said on Monday.
A day after the zoo's staff failed to revive the cub with lifesaving measures, including CPR, the initial results of an examination showed the panda was likely a female whose body displayed no obvious signs of trauma or infection.
"Her coat was beautiful. It was in very good condition," veterinarian Suzan Murray said at a press conference.
The cub was born on September 16 but had not yet been given a name, in line with a Chinese tradition that pandas are not named for 100 days. The arrival was cause for celebration among zoo officials and wildlife conservationists given the daunting odds for the endangered species reproducing in captivity.
Fewer than 1,600 giant pandas are known to exist in the wild, and about 300 live in zoos and wildlife centers around the world. Breeding is a critical challenge. One in five cubs born in captivity die in their first year of life, the National Zoo said on its website.
Preliminary results of an examination of the cub show the tiny animal had a discolored liver, which was hardened in some areas, Murray said.
"This can suggest there was a liver component to the death," Murray said.
Another unusual finding, according to Murray, was fluid in the cub's abdomen, normal for adult pandas but odd for a juvenile. Pathologists were analyzing the fluids, Murray said.
"The amount appears moderate to increased for such a small cub," she said, adding that further testing was necessary to confirm a cause of death.
The body of the cub weighed about 3.5 ounces (100 grams).
Zoo officials said they were concerned about the reaction of the cub's mother, Mei Xiang, who had given birth after years of failed efforts at conception, including five "pseudo pregnancies" in which her hormone levels and behavior indicated she was carrying a cub when she was not.
Her first cub, Tai Shan, was born July 9, 2005. Tai Shan is now at the China Conservation and Research Center for the Giant Panda in Wolong.
The zoo has used a Panda Cam to monitor Mei Xiang, who appeared to sleep well Sunday night and who ate her regular diet of bamboo, fruit and biscuits, the zoo said on its website.
"Watchers noticed her cradling an object, as she did before the birth of the cub. Scientists and keepers believe this is an expression of her natural mothering instinct," according to the zoo's website.
The cub's death was discovered Sunday morning after panda keepers and zoo volunteers heard a distress sound from Mei Xiang.
"We want to make sure that her behavior adjusts back to normal," said zoo spokeswoman Emily Grebenstein.
(Editing by Barbara Goldberg and Philip Barbara and Claudia Parsons)