'We hope we'll have a baby boom this year,' said Wang Chengdong, top veterinarian at the Chengdu Research Base for Giant Panda Breeding. 'Ultrasounds will take place this summer. A major reason for the baby boom last year was animal management - the improvement in food quality and environment and nutrition as well as reproductive technology.'

Of last year's 31 cubs, 12 were from Chengdu Panda Base: nine were born on the base, two born in Japan, and one at Zoo Atlanta in the US. The early signs of another bumper batch of baby bears are there. Mei Xiang, the panda matriarch at Washington's National Zoo, is showing a spike in hormone activity and zookeepers say she may be pregnant for the second time. She gave birth to Tai Shan nearly two years ago in the zoo after artificial insemination.

The giant panda is one of the world's most endangered species and the only wild ones are found on the mainland. The state forestry administration estimates that there are 1,590 animals in the wild - mainly in the mountains of Sichuan province - and 210 in captivity.

It's difficult to tell if a panda is pregnant, given that a baby panda is just one-900th its mother's weight at birth. And their gestation period varies - one panda at the base was pregnant for 324 days.

'We have 59 pandas here, but we need to increase the population to a self-sustaining number. Then we will begin research to devise the best reintroduction plan to release them into the wild. There are a couple of hundred in captivity, but we think a total of 300 is a safe number before taking risks,' Mr Wang said.

Captive pandas are notoriously poor breeders - they spend most of the year on their own, except during the mating season, which begins in March. Male pandas show little interest in sex - more than 60 per cent of male pandas in captivity show no sexual desire at all, and only one in 10 will mate naturally.

A classic example of this at the Chengdu base is Kobe, the biggest male at the facility, who has injured females during breeding and so is kept on his own out of harm's way, although his sperm has been used for breeding. A major advance in helping the panda breeding programme came in 1980, when scientists learned how to freeze panda sperm in liquid hydrogen.

Some of the methods used to encourage the males, such as showing them videos of mating pairs in the hope that 'panda porn' will help the bears get a bit frisky,

are well documented, although scientists say it doesn't have much effect and is a bit of an urban myth.

'Pandas don't watch TV any more than cats or dogs tend to watch TV. But they do listen, and vocalisation is important during breeding. The females often want

to do it, but the males are less interested,' said Sarah Bexell, director of conservation education at the base.

Females are fertile for just a few days each year and they play hard to get, although in captivity they are often more interested in sex than

the males.

Pandas follow a kind of one- child policy, with females generally giving birth to just one cub after a pregnancy lasting about 160 days. When two cubs are born, the mother will often abandon one, as she is not equipped to care for two.

'The population is more stable now because of conservation, and the numbers in captivity are rising strongly in places like the panda base here,' Mr Wang said.

The base has a steady supply of bamboo to feed the fussy eaters, with about 4,000kg brought in daily from the mountains, and bamboo cultivation is becoming a major industry in the hills near Chengdu.

What pandas do eat they find difficult to digest as they have an inefficient digestive system. This means they spend nearly 12 hours every day eating up to 25kg of bamboo shoots, leaves and stems. Bamboo flowers and then dies off about every 20 to 40 years, at which point the pandas have to move on to fresh pastures. In the 1980s, many pandas starved to death because the species of bamboo they like to eat died off and had to be reintroduced by conservationists.

Conservation efforts have helped to boost the population in the wild and Beijing has spent billions of dollars on reforestation in the panda's natural habitat. There were 33 preserves in 1999. Now, there are 60 and the giant panda area has been named a world heritage site. But the famously shy creatures need a lot of room to move around and global warming is affecting their habitat, with rising temperatures forcing them to higher altitudes and bringing them closer to one another. 'The pandas aren't being poached, but their habitat is being encroached on,' said Dr Bexell.

The mainland's panda breeding and conservation community is still upset after the violent death in February of five-year-old Xiang Xiang, the first captive-raised panda released into the wild. He was found dead in the snow in a remote mountainous area of Sichuan 40 days after scientists picked up his signal for the last time on a wireless tracking device. It seems that he was attacked by jealous males during the mating season and possibly pushed out of a tree to his death.

The death of Xiang Xiang just months after he was set free from Wolong - another panda centre two hours from Chengdu that has provided two pandas for Hong Kong's Ocean Park to celebrate the 10th anniversary of the handover - was a major setback for efforts to conserve the endangered species by releasing captive-bred bears back into the wild.

'Xiang Xiang died, which was sad, but our goal is to increase the population and scientists learned a lot from this. We learned more about how to choose the environment and what sex to reintroduce,' Mr Wang said.

It is still early days in the whole science of reintroduction. 'The problem with reintroduction is that we don't really know what will happen in the wild. We have reintroduced pandas that have wandered into cities, but there's

a lot we still don't know about freeing the creatures into the wild,' Dr Bexell said.

Experts at Wolong are now working on three action plans, associate chief engineer Zhou Xiaoping said.

'The first option is to send a female giant panda into the wild, because females are more easily accepted by wild pandas and a male one is usually regarded as a threat,' Mr Zhou said.

The other two options under consideration were releasing either a mother panda with her cub or a pregnant panda, because a cub could adapt to its new environment at an earlier age.

Beijing's gift of pandas to Hong Kong comes after a long history of using pandas to win diplomatic points, stretching back over centuries. In 1975, chairman Mao Zedong sent US president Richard Nixon a pair.

Why do pandas seem to capture the public imagination in ways that other animals don't?

Looking at Yaxing and Yashuang, 'sub-adult' bears who are four years old, and three-year-old twins Qinghe and Yongyong, all larking about at the Chengdu base, it is easy to see how giant pandas have worked their way into our affections. However, there is also a scientific explanation.

Dr Bexell said the reason people liked pandas was because they were neotenous, which meant they retained juvenile characteristics into adulthood. But Mr Wang said it was because they were rare - and just plain cute.