There's an unmistakable sexual tension at Wolong's celebrated giant panda enclosures on the misty upper slopes of Sichuan's bamboo forests. Early summer here provides an all-too-narrow window of opportunity for the handful of male breeding pandas on the world-famous reserve, and the prospect of imminent gratification hangs seductively in the air.
Qing Qing, Ying Ying and friends are waiting bad-temperedly - or as grumpily as this disarmingly docile creature gets in captivity - to begin the job at hand. The males must endure a frustrating wait until the moment is exactly right for their more reluctant and choosy breeding partners. As the females prepare to come into their brief period of oestrus, the males are barking and swinging from the branches in anticipation.
But if the male pandas' hopes are riding high on the activities of the next few days, so too are those of the scientists who have dedicated their lives to the preservation of China's giant panda, and who shoulder responsibility for the future success of this great symbol of global conservation.
At Wolong, a four-hour drive along a treacherous single-lane road from the provincial capital of Chengdu, they, with the help of the international community and the support of hundreds of panda lovers around the world, are painstakingly rebuilding the critically low population.
Last year, 34 cubs were born in captivity in China, setting a record for the 30-year-old breeding programme. This year, expectations are high that this number can be bettered.
According to Professor Tang Chunxiang, the chief vet at the China Conservation and Research Centre for the Giant Panda at Wolong: "Panda breeding here is successful and we have worked hard to overcome the many problems." Every avenue has been explored, from IVF to showing prospective couples "pornographic" videos of pandas mating in the wild.
Tang believes that without such forthright human intervention, the panda would now be extinct. "Every species must obey the natural law. The population is simply too small to survive on its own," he says.
"The human being has always tried to do his best to save the panda and give them more time on earth. This is our philosophy and also our obligation. If the giant panda is protected, then I believe the other wild animals - the whole biosphere - will be protected too."
But Wolong is reeling from the disclosure last week that one of its most high-profile projects - the return of a captive-bred giant panda to the wild - had ended with the animal being killed by rivals.
This has piled yet more pressure on the breeding programme, because the baby boom at Wolong is crucial to China's image in the conservation world. Its biological resources are among the richest anywhere, equal to one-eighth of all species and greater than all of Europe put together. But China has a total of 385 species perilously close to extinction, and even the giant pandas - the subject of intense international attention for three decades - lost almost half their habitat between 1974 and 1989.
Wolong was not immune to the destruction. A study by the Chinese Academy of Sciences in 2001, using former United States spy satellite pictures from the 1960s, revealed that the park had undergone substantial damage even after the reserve was established. China's breakneck development over the past decade has increased the pressure on land use even more.
Yet a survey published in 2004 delivered some unexpectedly good news to conservationists. Experts from China's State Forestry Administration and the conservation group WWF estimated that there were some 1,600 great pandas left, about 1,100 of them in the wild. The figure is about 40 per cent higher than had been thought.
One in 10 of this surviving, scattered population of a beast that has survived for nine million years resides within the 200,000 hectares of Wolong. The reserve also accounts for nearly two-thirds of the cubs born in captivity.
Yet the panda population remains desperately low, and survival depends not just on the Wolong breeding programme, and on similar programmes in zoos in the United States, Germany and Japan, but on China's 40 reserves. Established in 2003, they are home to about 60 per cent of the wild population of giant pandas, protecting more than 10,400 square kilometres of land in Sichuan, Gansu and Shaanxi provinces.
But, Tang says, human help can only go so far. Pandas are afflicted with a series of debilitating in-built weaknesses - a hangover from their extraordinarily long tenure on the planet - which make them highly vulnerable to the impact of man.
One of the biggest problems facing the species - classified as halfway between a bear and a raccoon - is its solitary nature. Panda males abandon their cubs, and - in another Darwinian own-goal - wild females select only the strongest cubs to keep alive. That comes at a significant cost to the population, as twins account for nearly half of births.
In the wild, dwindling numbers mean that solitary females, sexually active for only one-third of their lives, are increasingly isolated from potential mates and less likely to encounter a male during the two- to three-week mating season. To make matters worse, they are stubbornly choosy about who they mate with - a fact not lost on scientists at London Zoo who tried valiantly to persuade a reluctant Ming Ming to couple with Bao Bao. Their tempestuous, at times violent, liaison was eventually halted and both animals sent home in disgrace.
Pandas are frustratingly picky eaters, too. At Wolong, their famous diet of bamboo shoots is supplemented by meat, replicating more natural conditions. The supplement is critical when it is considered that less than one-fifth of the weight of shoots is converted into body weight. A deer gleans nearly four times the energy value from its food.
But for the carnivore-turned-herbivore, stomach complaints, particularly diarrhoea, are common, as are respiratory problems. Pandas are also highly susceptible to infection.
Watching the animals in captivity as they sit peacefully munching their way through piles of bamboo, it is easy to see their limitations as one of the great hunters of the forest. They may have long claws and a threatening bark, but captive-born youngsters are docile and happy to be handled by staff - even posing on the knees of tourists. They seem no match for the leopards and wolves that inhabit the slopes above Wolong.
But returning panda cubs to the wild is the next big challenge. Five years ago, Wolong opened a new 300,000-square metre enclosure on the upper slopes of the forest - a halfway house between captivity and the wild. Here, pandas are encouraged to take part in "running wild" training. At present, 10 adults are living in the enclosure.
In 2006, scientists went one step further, releasing the male Xiang Xiang completely into the wild. A global positioning system (GPS) transmitter was attached to his body and his movements monitored using software developed by Microsoft.
At first, Xiang Xiang did well, roaming over a two-kilometre area, gradually moving up the mountain as the bamboo shoots came into season. After a year, hopes rose that he had made the transition back to nature.
But, in February, disaster struck. Observers spotted traces of blood behind the panda as it dragged itself through the snow. Experts believe Xiang Xiang had been attacked by another male panda and was suffering from bite wounds. Tang believes the experiment shows that pandas can be returned to the wild, albeit with better self-defence training. He hopes to resume the programme later this year.
In the wild, pandas roam a territory of about two kilometres square, which they must mark out and defend against rivals. "We cannot help them, they must do this by themselves," Tang says. "All we can do is watch and learn for next year. Because they are born in captivity, they don't know how to build their territory. Their big problem is that when other pandas or predators enter their territory and are aggressive, they don't know how to react. We try to teach them, but the human teacher is not very good. Now we have many captive babies, but we need more research on how to reintroduce them to the wild. It is down to them to learn how to build their territory."
Tang came to Wolong in 1979, when it was little more than a few tents in the middle of virgin forest. The project was backed by WWF the following year. At that time, pandas were the symbol of thawing relations between the inheritors of Mao's China and the international community. Today, more than 110 people work in the state-of-the-art facilities. Tourists as well as international researchers make the long trek up into the mountains to see the work at first hand.
Yet, in spite of the success of the breeding programme, the message at Wolong is one of caution. China's booming economy is hungry for land and timber. Tourism is central to development efforts in the still pitifully poor rural areas, and new roads and hotel complexes are being built at a rapid rate. A new two-lane road is steadily snaking its way up the mountainside to Wolong. It will bring more tourists but also new challenges.
Professor Tang and his team will know in August how successful their efforts have been this year when they begin the process of testing the females with ultrasound to see how many of them are pregnant. All will have undergone both artificial insemination and natural mating, and it will not be until the cubs are six months old that they can be DNA-tested to establish their paternity.
Meanwhile, the giant panda is being hailed not just as the flagship global species for conservation, but as an important symbol in the sensitive issue of China's minorities. A statue at the gates of Wolong depicts a member of the minority Qiang population carrying a stricken bear as a Han doctor assists and a Tibetan girl holds a blood transfusion bottle.
Few species can have found themselves shouldering so many of man's hopes - their survival has been linked to everything from sustainable development to international peace among nations. Only the future will tell whether those aspirations will be realised.
Where: Smithsonian National Zoological Park, Washington, DC
This ferret was thought extinct until 18 were discovered in Wyoming in 1981. The Smithsonian breeding programme uses computerised genetic matchmaking. From those 18 animals, about 250 ferrets now live in breeding facilities and more than 300 survive in the wild.
Breeds apart: other species on the brink
MIAMI BLUE BUTTERFLY
Where: Florida University, Florida
The Miami blue, one of the rarest insects in the United States, was thought to have become extinct in 1992. Then, in 1999, a population of about 50 butterflies was found in the Florida Keys. The species was listed as endangered and the captive breeding programme started in 2003. About 2,500 captive-bred Miami blue caterpillars are now released into the wild each year, and more colonies of the butterflies were discovered last year on islands in the Florida Keys.
Where: Alligator River National Wildlife Refuge, North Carolina
The red wolf (Canis rufus) is the rarest wolf species in the world. After it was declared endangered in 1973, the 17 remaining wolves were captured, and 14 became the founders of a successful captive breeding programme. By 1987, enough red wolves had been bred in captivity to begin restoring them to the wild. An estimated 100 red wolves how roam North Carolina, and another 150 are part of the continuing captive breeding programme.
Where: KwaZulu-Natal Nature Conservation Service programme, Zululand, South Africa
The biggest of all turtles - and the fourth-largest reptile in the world - the leatherback is critically endangered thanks to man's encroachment on its habitat. The KwaZulu-Natal programme has been running on the northern Zululand coast for 36 years. Leatherback numbers have increased from five females in 1966 to more than 150 in 1993. The programme consists of surveying the turtles, running a hatchery and releasing hatchlings into the wild.
Where: Monkey World Ape Rescue Centre, Dorset
The Borneo Orangutan Survival Foundation UK has predicted that orang-utans will be virtually extinct within the next five years. The Monkey World Ape Rescue Centre is trying to breed them. The centre has 13 orang-utans, including five babies, three of which were born at the centre and two who came to them through the European Creche Programme.
Where: Hoedspruit Research and Breeding Centre for Endangered Species (the Centre), South Africa
The cheetah, fastest of all land animals, is also vulnerable - about 12,400 remain in the wild in Africa. The Centre was established in 1988 to run a cheetah breeding programme. Two captive-bred cheetahs were set free in 1993, and another two in 1996. The programme is considered a great success.
Where: Captive Wild Camel Breeding Programme, Zakhyn Us, Mongolia
Although there are some 1.4 million domesticated Bactrian camels, only about 950 live in the wild in China and Mongolia. The Mongolian breeding programme of this endangered species, the only one of its kind in the world, was set up in 2003. Using a process called "embryo transfer" - similar to human IVF techniques - the aim is to increase the numbers of wild Bactrian offspring each year by using surrogate domestic Bactrian camels to carry the embryos of the wild ones.
Where: Taronga Zoo, Sydney, Australia
The red panda is, like its distant relative the great panda, on the endangered species list. There is an estimated population of fewer than 2,500 mature red pandas in the wild, and their numbers continue to decline. Two red pandas were born earlier this year in the breeding programme at Taronga Zoo, which has the best breeding record in the Southern Hemisphere for this endangered species. Taronga has sent 20 red pandas to other zoos around the world.Reuse content