SCIENCE -- September 24, 2012 at 5:44 PM EDT
Panda Cub's Death Still a Mystery
Mei Xiang made distressed sounds at 9:17 a.m. on Sunday, alerting zookeepers that something was wrong with her baby. Video by Smithsonian's National Zoo.
The Smithsonian National Zoo hasn't yet confirmed what caused the death of the week-old panda cub, but an abnormal liver may have been a factor, according to the zoo's chief veterinarian.
The cub's tiny liver, which is smaller than a kidney bean, was an unusual color and hard to the touch, said chief veterinarian Suzan Murray at a press conference on Monday. This could be the result of a liver condition or disease, though more tests are needed to confirm that. The cub also had fluid in her abdomen between the gastrointestinal tract and the other abdominal organs, Murray added. Fluid in that region is not unusual for giant pandas but for such a small cub the amount appeared to be higher than normal.
The necropsy ruled out more common causes of cub death, like pneumonia. The cub, who appears to have been female, had a healthy heart and lungs, and the presence of milk in her stomach indicates that she had been nursing. There were no signs of internal or external trauma. They don't believe Mei Xiang, the mother, was at fault.
"We continue to mourn the loss of this cub," said Dennis Kelly, director of the zoo. "Every loss is hard. This one is especially devastating."
Meanwhile, animal keepers are closely watching Mei Xiang. The giant panda made distressed sounds Sunday morning, which alerted keepers that something was wrong with her baby. Zookeepers retrieved the cub using an emergency drill they had practiced: they distracted the mother while using a trash grabber to reach into the den and pull out the cub.
In their first year of life, pandas born in captivity have a high mortality rate: 20 percent for female cubs and 26 percent for males. And those numbers may be underestimated, said Pamela Baker-Masson, associate director of communications for the zoo. Of the seven cubs born at the National Zoo, Tai Shan is the only cub that has survived to adulthood.
Mei Xiang cradled a Kong toy throughout Sunday night, as she did during her pregnancies.
"I think it's very touching that she's cradling a Kong toy today," said Don Moore, associate director of animal care. "It's a mothering behavior, and we need to understand more about it."
This morning, Mei Xiang was interacting with zookeepers and beginning to eat bamboo, fruit and biscuits, all signs that she may be returning to normal behavior, Murray said. The Panda Cam was turned off while staff retrieved the cub, but is now back on so the public and zookeepers can continue to observe the pandas.
"Even though this cub didn't survive, this was a gift to everybody to be able to watch a carnivore in her den with her baby," Moore said. "Everyone got a glimpse into the secret life of pandas for a week, including us."