FIRST DATE PROMISING FOR PANDAS.

Byline: Dana Calvo Associated Press 

With a wanting moan, she stood up to greet him and ran her meaty paw along the fence. He was shy, perhaps not realizing how powerful her feelings for him were, but soon he sauntered over and touched her face.

Two giant pandas on loan from China were introduced to one another at the San Diego Zoo on Friday, where officials are hoping their union will be fruitful.

Bai Yun, the 215-pound female, is a 5-year-old virgin. Like most giant pandas, she will be fertile for only one day this spring, but she is already showing signs of going into heat, animal behaviorists said.

Shi Shi, the 15-year-old male, has spent nearly all his life in the wilds of China, leaving officials to guess at the number of little black and white pandas he fathered.

In early September, Bai Yun and Shi Shi arrived at the San Diego Zoo in two metal crates. Wild pandas live alone and interact with members of the opposite sex only to mate, so zoo officials put them into a 30-day quarantine.

At Friday's historical meeting, animal behaviorist Ron Swaisgood said Bai Yun ``wanted to go in and visit the male, Shi Shi.'' But officials are taking it slow, with brief, controlled interactions planned for the next few weeks.

``This is pre-breeding activity that we're talking about. It's important to prime our male in breeding. If you just take a male and introduce him cold turkey to the female, it's more likely to be an aggressive encounter,'' Swaisgood said.

As part of that pre-breeding introduction, the pandas have been communicating through their highly effective ``scent messages.'' The 225-pound Shi Shi has gone into Bai Yun's pen when she's not there and sniffed around. On his way out, he leaves his own marks.

``Sometimes, they even do a handstand and leave the scent on a high point on the wall,'' Swaisgood said.

Female pandas only produce eggs about once a year and are fertile for just over a day. Copulation lasts anywhere from two to 15 minutes, but it is always very vocal, scientists said.

``There's a lot of loud warbling sound that I couldn't even begin to describe. Incessant noise,'' Swaisgood said.

Bai Yun had one previous, unsuccessful mating attempt last year in China. But the male had problems with mounting orientations. ``They had 15 minutes together, and he couldn't quite figure it all out,'' Swaisgood said.

Bai Yun and Shi Shi have drawn 10 percent more visitors to the zoo this year than last. Annual memberships to the zoological society are at an all-time high for the winter months, with 223,000 households signed up.

Bai Yun and Shi Shi are the first pandas to be allowed into the United States since 1993 when officials banned the importation of the species.

If Bai Yun does conceive and carry to term a baby panda, she will be pregnant for about four months. Newborn pandas are usually the size of ``a stick of butter - four ounces,'' Swaisgood said, and they are dependent on their mothers for two years.

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Photo: Bai Yun, a 5-year-old female, glances out from her zoo pen.

Associated Press