San Diego’s Giant Pandas Begin a Delicate Courtship

She’s frisky and curious. He’s the strong, aloof type.

Can they create a bear-apparent?

Such is the scientific / zoological / geopolitical question being pondered at the San Diego Zoo about Bai Yun and Shi Shi, giant pandas on 12-year loan from China.

In the mind’s eye of the public, the two are a May-December kind of couple: She’s young, cute and energetic; he’s older, rugged and a bit battered by life.

But the problematic truth is that the female, Bai Yun (White Cloud), and Shi Shi (Rock) had never met before they shared adjoining crates on a VIP flight from Shanghai in September.

Even after arriving in San Diego, they were kept apart. Panda mating is dicey, even risky. Fights are common.

In the wild or in captivity, male and female pandas are solitary creatures and don’t seem to like each other much. The female is only in season for one day, maybe two, per year, and some years females skip the process altogether.

Nobody knows for sure, but panda specialists gathered here think that Bai Yun’s estrus will arrive in the next few weeks, as the sap rises and the first buds of spring coax forth the stirrings of memory and desire.

In anticipation of the Big Day, Bai Yun and Shi Shi have been allowed limited fur-to-fur interludes in a behind-the-scenes exercise yard at the zoo. This week the two may also be put together on public view at the panda enclosure, where they have been stars since being put on exhibit in November.

Their first introduction went well.

She approached him. He honked, growled and barked. They sniffed noses. She walked away. They tussled a bit. He went to sleep in his cave. She dozed nearby.

In panda courting, that’s considered a successful first date. She signaled availability; he signaled dominance.

“There were lots of messages sent between the pair,” said panda keeper John Michel. “Bai Yun said, ‘I’m curious and I want to be together,’ and Shi Shi said, ‘Stay at arm’s length for now.’ ”

Further encounters are planned for the pair, the only pandas in the United States besides the forlorn male in the National Zoo in Washington.

It’s a delicate matter. Too little contact and Shi Shi and Bai Yun will be strangers when it matters most. Too much familiarity could breed contempt and boredom.

Captive breeding of pandas has always been difficult. Even at China’s Wolong Giant Panda Conservation Centre, the record has been spotty.

A decade of trying by Ling Ling and Hsing Hsing at the National Zoo captured the nation’s attention and resulted in four pregnancies. None of the offspring lived beyond a few days. Now Ling Ling is dead, and Hsing Hsing lives alone and issue-less.

Bai Yun, who was born in captivity, had her first estrus last spring at age 5. She did not breed, either because the male was not competent or because her estrus was not full-fledged.

Shi Shi, who is between 11 and 15, was born in the wild and mauled in a rutting-rights fight with another male. A question remains over whether that traumatic experience has left him unwilling to make another breeding attempt.

“We’re hopeful, but there are no guarantees in this business,” said Don Lindburg, head of the behavioral division at the zoo’s Center for the Reproduction of Endangered Species. “We’re hopeful they’re motivated and get the mechanics right.”

If Shi Shi is not motivated, the zoo may use artificial insemination, either with Shi Shi’s sperm or frozen sperm from pandas in European zoos. But frozen sperm is considered a poor substitute; the freezing process slows down the sperm’s all-important motility.

By watching the pair closely, scientists from San Diego and China hope to unravel some of the secrets about panda communication and breeding. With the wild panda population at less than 1,000, captive breeding takes on added importance.

“This is the world’s most popular animal, but we know very little about its biology or behavior,” said Ron Swaisgood of UC Davis, who is working on the zoo’s panda team headed by Lindburg.

By studying the pair’s scent-markings and urine and Bai Yun’s vaginal cytology, scientists hope to know when Bai Yun is ready for breeding, and, in a more general sense, how pandas communicate by spraying on trees and by sniffing each other’s droppings.

A long-range goal, now just in the talking stages between Chinese and San Diego panda experts, is to release captive-born pandas from Wolong and elsewhere into the wilds of Szechwan Province to bolster the population and strengthen its genetic pool.

If the secrets of panda urine and scent-marking can be unlocked, it could be helpful in establishing captive-born pandas in the wild. Urine and scent smells could be distributed to make the new arrivals feel at home and encourage them to colonize.

Panda DNA is being studied to find a better method of counting pandas in the wild. Also being probed is just how conception occurs in pandas: whether ovulation precedes copulation, or whether, as in some animals, ovulation occurs because of copulation.

San Diego, always quick to adopt zoo animals as members of the extended civic family, has taken to Bai Yun and Shi Shi in a large way. San Diego magazine included them in its annual “people to watch” list, an honor much coveted by politicians and business leaders.

If an offspring is born, the San Diego Zoo will pay the Chinese up to $600,000, depending on how long it survives. But any cub remains Chinese property and will be shipped to Wolong within three years.

In their first meeting, Shi Shi got high marks for showing interest but not aggression. A common reason for the failure of captive breeding attempts of pandas is a lack of interest on the male’s part or a revved-up hostility.