When San Diego Zoo visitors drop in on Bai Yun, the giant panda, they see what most humans see when they look at these endangered creatures: a Beanie baby come to life. Cute. Cuddly. Too toylike to be real.

When zoo staff members look at this 23-year-old matriarch, however, they do not see cute or cuddly. They see pioneering and prolific. A walking textbook that is almost too priceless for words.

“I might be bragging because everyone loves her, but I think Bai Yun is the most scientifically influential panda that has ever lived,” said Barbara Durrant, Henshaw Chair and director of reproductive physiology for the San Diego Zoo Institute for Conservation Research. “She has given us more information about giant pandas than any panda ever.”

Since coming to the San Diego Zoo from China in 1996, Bai Yun has been in the rare-animal milestone business. And last week, she hit another one.


After giving birth to six of the 13 surviving panda cubs born in this country, Bai Yun may have reached the end of her reproductive years. After surprising everyone by going into season this spring, Bai Yun was artificially inseminated. Panda-watchers were guardedly hopeful, but on Monday, the zoo announced that multiple tests revealed she was not pregnant.

Given her age, and the fact that giant pandas are only in season once a year, this was probably the zoo’s last chance for another Bai Yun baby. But Bai Yun’s legacy? From tricky medical procedures to impressive training discoveries, this giant panda’s contributions have been, well, huge.

“Everything we have learned here has been because of Bai,” said lead panda keeper Kathy Hawk, who has been with Bai Yun since the panda’s arrival. “She is the foundation of what we do here.”

There are an estimated 1,864 giant pandas in the wild and 300-plus living in captivity. Most of the pandas in captivity live in panda reserves in China, with smaller numbers living in zoos throughout the world.


In the United States, the San Diego Zoo and the National Zoo in Washington, D.C., each have three pandas on site. Zoo Atlanta has four, and the Memphis Zoo has two. Whether they are in Atlanta or Adelaide, these roly-poly animals draw besotted crowds.

“It’s almost like they are this romanticized, larger-than-life thing,” said Carl Winston, director of San Diego State’s L. Robert Payne School of Hospitality and Tourism Management. “It is a natural human tendency to love cuddly things, but how many of us have ever cuddled a panda? There is that rarity factor. It is the things you can’t get that you are attracted to.”

Landmark loan

When Bai Yun and the male panda Shi Shi came here, they were the first pair of giant pandas to come to a U.S. zoo as part of a landmark panda-loan agreement with China. Three years later, in 1999, the rare Bai Yun did a historical thing – she gave birth to Hua Mei, the first surviving giant panda ever born in this country.

Five cubs fathered by Gao Gao followed, making Bai Yun the most prolific giant-panda mother in the U.S. As part of the panda-loan agreement, all panda cubs go back to China after their third birthdays. Hua Mei has since given birth to 11 cubs, and Su Lin (born in 2005) is the mother of two surviving cubs.


In addition to her cubs, Bai Yun blessed the world with a bundle of information. The Chinese government began tackling the dwindling panda population in the early 1960s by setting up reserves, and giant pandas were being bred in captivity. But before the pandas came to San Diego, there wasn’t much in the way of scientific research about them.

Even the most basic things – How do you measure a panda’s hormone levels? What is the normal blood pressure of a panda? – were a mystery. And then there was the mother of all panda puzzlers: How can you tell if a panda is pregnant?

Because pandas are so big (Bai Yun weighs about 240 pounds) and panda babies are so tiny (usually less than 4 ounces at birth), there are no outwardly visible signs of pregnancy. And because false pregnancies in giant pandas have the same hormonal profiles as real pregnancies, telling the false from the true was tricky. Even for the experts.

“With the early animals, whether they were bred or inseminated, people just waited and hoped. The first time Bai got pregnant, we sat with her and just waited for her to give birth,” Durrant said. “Until a few days before it happened, we didn’t know if she was pregnant or if it was a pseudopregnancy.”


‘Textbook’ panda

Thanks to Bai Yun, they know more now. In terms of her reproductive life, Bai Yun has been like a big, furry clock. She could be counted on to go into estrous (a period of sexual receptivity) in March or April, mate, and then deliver a cub in July or August. The new world of panda science had a one-bear control group. And she lived right here.

“We have often described Bai Yun as the ‘textbook’ panda because her behavior and physiology during her estrous, pregnancy and cub-rearing periods has been remarkably consistent,” said Megan Owen, associate director of applied animal ecology for the San Diego Zoo Institute for Conservation Research.

In addition to being reproductively reliable, Bai Yun turned out to be a smart panda patient. Using food (apples and honey-water are big favorites) and a clicker, her keepers trained her to lie still for ultrasounds, X-rays, vaginal swabs and other procedures. She can even urinate on command.

Bai Yun’s cooperation has resulted in data that led to great strides in pregnancy detection methods, and that information has been shared with the other zoos and with China.


“I did get a lot of urine samples from Bai Yun,” said Erin Willis, who worked on a Memphis Zoo study that helped develop a pregnancy test for giant pandas. “I think I requested samples from the San Diego Zoo three to four days a week of her estrous cycle. Bai Yun is a trooper.”

Bai Yun will also allow zoo staff brief access to her cubs, which has given the zoo a huge database of information on cub growth, nutrition and behavioral development.

“Bai Yun and the other pandas here at the San Diego Zoo have challenged us to do more for conservation of pandas in China, stimulating research on pandas that, when applied, helped us all turn around the breeding problem,” said Ron Swaisgood, director of applied animal ecology for the San Diego Zoo Institute for Conservation Research. “Some of that knowledge has been applied to research in conservation on pandas in the wild, too.”

Must-see attraction

If she were only a reliable breeder and an agreeable patient, Bai Yun would be an invaluable member of the San Diego Zoo family. But she is also a star in the much-watched panda universe.


While there is no way to track how many visitors stop at an individual exhibit, the panda habitat has always been on the zoo’s must-see list. And in the cyber world, the panda webcam is the most popular of the zoo’s animal cams and the panda blogs draw more comments than any other zoo blog. Many of those comments have to do with Bai Yun – her beauty, her mothering skills, her prowess with puzzles.

Visitors adore those adorable cubs, but they love and respect the mother.

“I almost want to say that she is legendary,” said Wendy Perkins, who moderates all of the zoo’s blogs. “Through the Panda Cam, people have been able to watch her from the minute each cub is born. They are amazed by how gentle a wild animal can be. They have watched her raise six cubs now, and they are astounded by how deftly she handles them. She knows what she’s doing.”

According to the current five-year loan-agreement with China, the zoo pays $500,000 a year for the pandas and $100,000 a year to a technical assistance fund. All of the money goes to the China Wildlife Conservation Association. The contract will keep Bai Yun and Gao Gao here through 2018.


After that, no one knows. Pandas in captivity can live to into their 30s, so will Bai Yun and Gao Gao retire here, or will they go? Will the San Diego Zoo’s reproductive legacy continue with a new pair of pandas? It is too early to speculate about what will happen next, but the people who know her best hope that Bai Yun’s San Diego story is just getting started.

“Things don’t stop because there is no baby. Now we will be dealing with geriatric pandas, and what we find out will be helpful to other institutions as their pandas age,” keeper Hawk said. “My opinion is that I would love to have Bai spend the rest of her life here. She was 5 when she arrived, and I would love for her to be here at the end.”