Millions are wondering: Is she, or isn't she?

Lips everywhere are whispering: Is it true that she is pregnant?

All of her fans hope the answer is yes, but the experts are still in doubt.

A report in mid-June from the Wolong Nature Reserve in southwest China's Sichuan Province said Hua Mei, a US-born panda that will celebrate her fifth birthday in August, is expecting.

That report has not yet been proven to be fact, but it has certain proven how popular Hua Mei really is.

"Our phones have become Hua Mei hotlines," said Wang Pengyan, deputy director of the Wolong Nature Reserve, which Hua Mei now calls home.

It has been five months since the giant panda returned to her ancestral home from the United States but in the eyes of her adoring fans, this first overseas-born panda returnee is still the brightest star in the endangered animal firmament.

It is true that Hua Mei successfully mated with a panda named Ling Ling on May 2, greatly increasing her chances of conception. She later received four rounds of artificial insemination.

If successful, she should give birth in September, said Wang.

"We are not sure if she is pregnant now, because so far, we have no way of being certain that a panda is pregnant until two weeks before she delivers," said Wang.

The female panda is normally sexually mature at four to five years old. The breeding season for the giant pandas in captivity at Wolong usually runs from March to May.

Pandas can only get pregnant once a year and give birth to one to two cubs each time.

Giant pandas have a low fertility rate even in the wild, and it is lower when the animals are in captivity.

For long periods, more than 60 percent of adult male giant pandas in protected areas or zoos show no interest in breeding.

Only 10 percent of them are capable of mating naturally, and just 30 percent of female giant pandas actually become pregnant and give birth.

Determining pregnancy after breeding remains a problem for scientists. Hormone or ultrasonic examinations, which are frequently used on other animals, do not work well with pandas and frequently give false results, said Huang Yan, deputy chief engineer of the China Panda Protection and Research Center at Wolong.

"The panda cub usually weighs about 100 grams (3.5 ounces) when it is born, just like a little pink mouse. It is very difficult to detect its movement in the body of a mother that weighs some 100 kilograms (220 pounds)," said Huang.

Another peculiarity of panda pregnancy is the phenomenon of delayed implantation. A fertilized giant panda egg does not immediately implant on the mother's uterine wall, but instead floats around in her reproductive tract for varying lengths of time. As a result, no one knows precisely the length of the giant panda's actual gestation period. The time between mating and birth can last anywhere from 83 to 181 days.

"Except the occasional listlessness, we haven't see any signs of morning sickness in Hua Mei. So the answer to the riddle will only be unveiled in September," said Huang.

Hua Mei, meaning "China-America," was born in 1999 to Bai Yun and Shi Shi, a panda couple leased by China to California's San Diego Zoo in 1996 as part of a 12-year research cooperation program.

Under the contract, cubs of pandas abroad belong to China and must be returned after they are three years old.

Hua Mei returned to Wolong this February, where she met her father Shi Shi, who returned last year. Bai Yun, Hua Mei's mother, remains in San Diego with another male, Gao Gao, and their one-year-old son Mei Sheng.

Hua Mei has fully acclimatized to the diet zoologists have tailored for her, said Zhang Guiquan, deputy director of the reserve, who arranges and overlooks panda feeding and breeding.

A special team is set up to take care of panda mothers-to-be.

"Our vets have increased routine checks on her recently, to check her breath, droppings, appetite and mood," said Zhang. "The results show Hua Mei is healthy and in good spirits. This lady has gained two kilograms over the past five months and weighs about 96 kilograms now."

Pandas are among the world's most endangered animals. The State Forestry Administration reported in June that the number of pandas in the wild in China has increased more than 40 percent from 1,110 in the 1980s to 1,590 in the most recent survey.

However, a portion of the increase may be attributable to improved survey methods, and the animal's existence remains seriously threatened by a loss of habitat and a low rate of reproduction.

(China Daily, China.org.cn July 12, 2004)