SCIENCE WEDNESDAY -- August 28, 2013 at 2:31 PM ET
New Technology Demystifies Panda Pregnancies
Mei Xiang delivers a panda cub on August 23. Video by Smithsonian's National Zoo.
On Friday afternoon, a live panda cam captured giant panda Mei Xiang at the moment her water broke, and two hours later, a healthy panda cub entered the world with a loud squawk. Mei Xiang immediately picked up her squealing 4.8 ounce cub and began cradling it.
The zookeepers breathed a tremendous sigh of relief. They were devastated last year when another cub, a female, died unexpectedly six days after her birth due to liver damage caused by underdeveloped lungs.
When it comes to reproduction, the odds are stacked against pandas. There is a narrow 36-hour window each year when the panda can conceive. The pandas prefer solitude, seeking others' company only during that breeding period. If the pandas fail to mate on their own, the zoo staff uses artificial insemination to increase their chances of getting a cub.
Plus, panda pregnancies are notoriously difficult to monitor because the animals show spikes in hormones whether or not the pregnancy is viable. In September 2012, the NewsHour reported on the many challenges of panda pregnancies, from conception to birth.
But in just a year, panda scientists have developed a new arsenal of tools to better detect and monitor panda pregnancy.
"Our expansive panda team has worked tirelessly analyzing hormones and behavior since March, and as a result of their expertise and our collaboration with scientists from around the world, we are celebrating this birth," said Dennis Kelly, director of the Smithsonian's National Zoo in a statement on Friday.
Mei Xiang has been under intense scrutiny since an artificial insemination procedure in March, said Pierre Comizzoli, reproductive physiologist at the Smithsonian's National Zoo. Following the procedure, the staff watched the panda closely for signs of a potential pregnancy. And the signs were there. She built a nest, began cradling her toys and her appetite waned, all indications that she was preparing to give birth.
But it's not that simple. After pandas mate, the fertilized egg doesn't implant itself in the uterine lining for weeks, even months, which means zookeepers never knew when to expect a cub.
Chief veterinarian Suzan Murray examines newborn giant panda cub on Sunday. Photo by Courtney Janney/Smithsonian's National Zoo.
"Panda watch" at the National Zoo began in early August, after Mei Xiang's progesterone showed a second spike, an indicator that the fertilized egg had implanted in the uterus -- though it also could have been signs of a pseudo pregnancy.
But this year, the veterinarians at the zoo had one advantage over past years: a due date. Twice a week for about a month, zoo staff froze urine samples collected from Mei Xiang's den, and sent them to their partners at the Memphis Zoo. There, scientists analyzed the urine for prostaglandin, a lipid compound that promotes contractions during labor. By tracking the prostaglandin levels, scientists could better predict when Mei Xiang was getting ready to give birth, said Andrew Kouba, director of conservation and research at the Memphis Zoo.
The test has been pretty accurate so far, give or take a day, he says. The prostaglandin assay predicted the July 15 birthdate for Zoo Atlanta's twin panda cubs "right on the nose," and estimated Mei Xiang's due date for August 24. (She delivered her cub on August 23.)
"It's really telling us if something's going to happen, it's going to happen in those two or three days, which is kind of convenient," Comizzoli said. "It's one more element for the explanation of this complex pregnancy phenomenon of the panda."
Having a due date gives the panda staff time to get ready, Kouba said. It gives the staff the time to bring in specialists to help monitor and prepare for the cub. And, he added, it focuses precious staff time and attention.
"A lot of man hours go into watching pandas, waiting for them to give birth. If you have a better idea when it will happen, you may not have to have people watching around the clock for weeks on end," he said.
But the prostaglandin peak will also occur in the case of a pseudopregnancy. Again, proof that nothing when it comes to panda reproduction is simple.
Beth Roberts, research fellow at the Memphis Zoo, who developed the prostaglandin test and made the predictions about giant panda due dates at Zoo Atlanta and the Smithsonian's National Zoo. Photo by the Memphis Zoo.
Also for the first time this year, panda scientists at the National Zoo inseminated Mei Xiang with semen from two males. In the coming weeks, a paternity test will determine whether Tian Tian, the National Zoo panda, or Gao Gao from the San Diego Zoo is the father. Another new technology emerging in the field is thermal imaging, which has allowed the San Diego Zoo to see twins, even triplets, in their panda Bai Yun's pregnancies. (The National Zoo has not yet adopted that technique.)
The Memphis Zoo has also been in the process of developing what could be the first panda pregnancy test. Fetuses are invisible to ultrasounds until two or three weeks before birth, Kouba said.
But Memphis Zoo researcher Erin Willis found that elevated levels of ceruloplasmin, a protein affected by inflammation, in the panda's urine could determine whether the animal was pregnant as soon as one week after conception. Using this test, Zoo Atlanta and Edinburgh Zoo found out they were expecting cubs this summer, Kouba said.
Thermal imaging technology shows when two fetuses, shown here in red, may be present. Photo by the San Diego Zoo.
But he cautions that the test can't predict a healthy cub. And for a few moments on Saturday night, the zoo staff feared that history was repeating itself when they saw a still, silent cub on the floor of Mei Xiang's den. The second stillborn cub, born 26 hours after the first, had horrible deformities, missing parts of its skull and brain.
Comizzoli said the surviving cub appears healthy, but the next six months are still high risk for the newborn.
"We are crossing our fingers and hoping for the best," he said.
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