Smithsonian National Zoological Park l Friends of the National Zoo



Panda Pact

A new agreement with China keeps pandas at the Zoo.

By Peter Winkler

Wind chilled the bones but not the spirits of the small crowd gathered at the panda habitat on January 20, 2011. The shivering guests, who included U.S. Secretary of the Interior Ken Salazar, watched intently as two men sat down at a table. Clad in dark suits and crimson ties, they were Dennis Kelly, director of the Smithsonian’s National Zoo, and Zang Chunlin, secretary general of the China Wildlife Conservation Association.

Snake receives eye injection.

Tian Tian and Mei Xiang, the Zoo's giant pandas. (Jessie Cohen/NZP)

Lying before Kelly and Zang on the red-draped table were a pair of black binders, each containing a copy—one in English, one in Chinese—of a new agreement between the two institutions. Behind the signatories cavorted the true stars of the day—Mei Xiang and Tian Tian, the Zoo’s giant pandas. The agreement confirms that the Zoo will likely remain their home for the next five years. (That likely is because there’s the possibility of exchanging pandas if our cub drought continues.) Any cub born at the Zoo will stay here for the first four years of its life, then head to China. In exchange for all this, the Zoo will contribute funds for conservation efforts in the bears’ homeland.

You won’t be surprised to learn that plenty of footwork led up that magic moment at the panda habitat. Kelly and other Zoo officials traveled twice to China to hammer out details of the agreement. Senior scientist Dave Wildt and his colleagues documented the Zoo’s long record of panda science, demonstrating to the U.S. Fish and Wildlife Service (which must approve the importation of any endangered species) that the Zoo’s pandas are serious research subjects as well as a popular animal attraction. After all, what Kelly and Zang signed was no mere loan deal. It was a Giant Panda Cooperative Research and Breeding Agreement. Three key words from that title—cooperative, research, breeding—describe both the Zoo’s panda heritage and its hopes for the future.


Each year for more than a decade now, wildlife biologist Bill McShea has spent two months in China. He ventures far out of the cities, into “the middle of nowhere,” to find wild pandas and their neighbors, such as Asiatic black bears and takin.

He doesn’t go alone. With him come Chinese wildlife workers eager to polish their skills. “You can’t go to school in China for wildlife management,” McShea explains, so opportunities for hands-on training are prized. “Our job,” he says, “is to say that these are the things wildlife people need to know.”

McShea teaches his Chinese colleagues how to conduct censuses and surveys of large mammals, such as the approximately 1,600 giant pandas that live in the wild. His colleague Melissa Songer shows how to use geographic information systems (GIS) and other high-tech tools for tracking wildlife.

Green tree python

Mei Xiang (Jessie Cohen/NZP)

“They love it!” McShea says of his students. Ninety percent of them work on Chinese wildlife refuges, so they keenly appreciate anything that helps them become more effective at their jobs. For his part, McShea loves “mentoring people along the way” and knowing that he’s “making a real contribution” to wildlife conservation in China.

Like McShea, Dave Wildt, who heads the Zoo’s Center for Species Survival, has plenty of China stamps on his passport. He coordinates the National Zoo’s panda programs, staying on top of happenings as far apart as Washington, D.C., and Wolong, China. “I keep everyone abreast of what’s going on,” he says.

Wildt’s work has given him abundant opportunities to further international cooperation on behalf of pandas. In 1996, he went to China as part of the Conservation Breeding Specialist Group, which explored issues in the captive breeding of pandas—a notoriously difficult challenge. “It was,” he says, “a terrific opportunity to get involved with China.”

Two years later, Wildt took part in an international team that undertook a biomedical survey of some 60 giant pandas. The group amassed “wonderful research,” and Wildt relished the opportunity for “working hand in hand as partners.” It’s important, he stresses, for American panda experts to resist the temptation to head to China “as missionaries.” Indeed, Wildt’s goal is “training ourselves right out of a job” as China’s corps of panda experts grows.

One of those experts recently demonstrated that sharing panda wisdom is a two-way street. Tang Chunxiang is the director of the Bifengxia Base, the panda reserve that is Tai Shan’s new home. “He’s bred more giant pandas,” says Wildt, “than anyone on the planet.” When Mei Xiang went into estrus this past January, Tang flew to D.C. to aid in efforts to mate her with Tian Tian. “We had great, synergistic, collegial discussions,” says senior curator Brandie Smith, whose portfolio now includes the pandas.


The giant panda “is one of the most fascinating species on Earth,” says Wildt. It owes much of its allure to mystery. The uniqueness of the giant panda means puzzles aplenty for scientists. As Wildt notes, “we still have much to learn about panda reproduction.”

One of the top challenges to understanding the wild lives of giant pandas is that they live only in remote, rugged mountains in China. According to a white paper prepared by Zoo scientists, the terrain “makes accurate surveying nearly impossible.” Scientists also know less than they would like about the “type and quality” of panda habitat.

All that said, National Zoo scientists have learned a lot about giant pandas in the past decade. Under the terms of the
Zoo’s agreement with China, scientists have studied these beloved bears both in the wild and in captivity. Based on field research, scientists are fairly certain that “wild pandas live in highly fragmented isolates, many of which do not have sustainable populations.”

To address that problem, McShea, Wildt, Songer, and colleagues have been exploring the possibility of creating “corridors” of forests that link isolated habitats. Such corridors would give giant pandas more options for movement and mate selection. They might also assist with the reintroduction of captive-born pandas into the wild.

Such reintroductions are a distinct possibility, say both McShea and Wildt. There remain good pieces of habitat toward the northern and southern edges of the panda’s range, and the captive population is burgeoning. Identifying “new landscapes for giant panda reintroduction” is one of the key research goals scientists will pursue under the new agreement.

Green tree python

Tian Tian (Mehgan Murohy/NZP)

Scientists and keepers have also studied the giant pandas in their care, amassing a wealth of knowledge that was unimaginable only a few decades ago. They have learned, for instance, vastly improved techniques for maintaining the bears’ health and enriching their lives.

National Zoo scientists, in particular, have become adept at studying the genetic relatedness of captive pandas, and they help their Chinese colleagues maintain an up-to-date studbook of these endangered animals. This helps ensure that breeding recommendations are genetically sound, avoiding inbreeding.

The result of all this gathering and sharing of knowledge is a larger, healthier captive population, In 1998, some 120 giant pandas lived in 19 zoos and breeding centers worldwide. Today, there are 319 captive pandas at 52 institutions around the globe. The captive population, Wildt says, is on the cusp of being self-sustaining.


That doesn’t mean, of course, that scientists wouldn’t welcome a tiny, new, pink, genetically appropriate bundle of panda joy. Indeed, senior curator Smith was crystal clear about her main hope for this new agreement: “babies, babies, babies!”

Smith is not alone in her hopes. When Mei Xiang showed signs of estrus this past January, the entire Zoo community kicked into action. Scientist Janine Brown, who runs the Zoo’s endocrinology lab in Front Royal, put things plainly: “We really need to get her pregnant this year.”


Born in 2005, Tai Shan was the only panda cub in Zoo history to reach adulthood. (Jessie Cohen/NZP)

That’s easier said than done, as Zoo folk know all too well. Part of the problem is that female giant pandas come into estrus only once a year, for 24 to 72 hours. As Wildt puts it, pandas devote less than one percent of their life spans to reproduction. Once estrus ends, the window of opportunity slams shut for another year.

To avoid any lost opportunities, keepers and scientists work together to monitor Mei Xiang. The former watch carefully for any swelling in her vulva. The latter measure hormones in her urine. They pay special attention to estrogen, watching daily or even hourly as it rises over the course of a week and then falls back to baseline levels. Once Mei Xiang’s estrogen level has returned to normal, she is at her most fertile.

And then what? First, keepers give Mei Xiang and Tian Tian a chance to do what comes naturally. They carefully arrange an introduction between the two bears. “Every year,” says Brown, “Tian Tian gets a little closer to getting it right.” But he’s never managed to actually inseminate Mei Xiang. At that point, nature gives way to science, and reproductive experts inseminate Mei artificially.

Then comes the waiting. Panda infants are tiny, so expectant mothers don’t show the way some other animals do. Pandas, moreover, are prone to a phenomenon called pseudopregnancy. Females will engage in maternal behaviors such as nestbuilding, and their progesterone levels will rise. Yet they never give birth. Perhaps the embryo died and was reabsorbed into the mother’s body; perhaps it never existed. Scientists are still teasing out the nuances of this baffling behavior.

At the Zoo, the waiting comes with much wondering. Why, everyone wants to figure out, has Mei Xiang not produced a cub since Tai Shan’s birth in 2005? Brown checks off the possibilities: “The artificial inseminations have been perfect. The hormone levels are right. The semen is good. It’s a mystery.”

One possible clue to the mystery is that Mei Xiang has been coming into estrus earlier in the year than before. She used to show signs of fertility in March; now she’s ready in January. Brown is not sure why Mei’s cycle has shifted, nor what its implications are for her ability to reproduce.

Panda Possibilities

Chill winds still blow through the panda habitat. They don’t bother the cold-loving bears, nor do they deter hardy admirers. Before long, though, those icy shafts will give way to spring breezes laden with warmth and humidity and hope.

Zoo staff perform an ultrasound examination on Mei Xiang. (Mehgan Murphy/NZP)

By then, the memory of the agreement signing will be faint. But the agreement’s importance will be no less profound. Cooperation will still thrive, as Chinese and Americans work together to study and protect these endangered icons. Research will continue to peer into the shadows of their little-known lives.

And breeding? No quick answer there, alas. Giant panda gestation can take three to six months. By then, the city’s famed cherry blossoms may have come and gone. Washingtonians will be planning summer vacations. And the Zoo’s panda team will wait impatiently to learn if their efforts to nudge nature have born fruit.


—PETERWINKLER is the editor of Smithsonian Zoogoer.



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Smithsonian Zoogoer 40(2) 2011. Copyright 2011 Friends of the National Zoo. All rights reserved.