In tiny villages, home to Li and Miao communities, the tattooed old folk still tell stories about gibbons. Stories about the pair of orphans driven out by an evil stepmother, who hid in the trees and turned into apes; or the bet between the gibbon and the earthworm over who could climb the best. Few of these storytellers, however, have seen a gibbon.

 

The tales are told in Hainan, China’s southernmost province. Once a sleepy backwater, the island is now a top tourist destination, known for its white-sand beaches and golf courses. It is also the last stand of the Hainan gibbon. Forget orangutans, tigers and giant pandas: with just 26 or so left, this is the world’s rarest mammal.

Scientists press China for action plan to save Hainan gibbons

The Hainan gibbon has had it tough for some time. Visiting naturalists in the 19th century described the apes as rare. They were hunted heavily. Boiling a whole animal for a few days until it was reduced to a hairy paste was said to produce a potent traditional medicine. Chopsticks made from their long arm bones could supposedly be used to test for poison. Later, its forests were chopped down for timber and to make way for agriculture, worsening the ape’s plight.

By the 1980s, the species was in dire straits, with only a few survivors in remote, forested mountains. They may have been saved by sheer luck. In one story, shortly after a hunter shot one of the last gibbons, his entire family died of some horrible disease, and killing gibbons became bad luck. Whether or not the story is true, a handful of animals some­how clung on in a nature reserve at Bawangling. I was privi­leged to come face-to-face with some of these survivors early one morning in 2010. There were seven of them, feeding, playing and grooming in the treetops: more than a quarter of all the Hainan gibbons left on Earth.

The 300 square kilometres of Bawangling’s forest are frag­mented by roads, power lines and plantations of rubber and pine. The gibbons are restricted to a 15 sq km patch, where, until recently, they lived in three social groups. Local rangers have monitored them for many years. The group I saw in 2010 was Group B – uniquely used to humans, which allows researchers to get reasonably close. Group A is much more wary and usually vanishes before you can get anywhere near. Group C, which only formed a few years ago, has set up its territory close to the edge of the forest patch. Villagers in a nearby Miao village can hear them duetting at dawn every morning.

Hainan forests in peril

All three groups are breeding successfully, yet the overall population has stayed below 30 since the reserve was estab­lished, in the 1980s. As they mature, young gibbons leave their social group and disperse into the forest, but in Hainan they rarely form new groups.

Getting to the bottom of what happens to these solitary animals is key: normally, new social groups drive population growth. Maybe the gibbons have simply run out of space. Their small patch of forest, on the slopes of Futou Ling moun­tain, may also not be the best habitat for a species that once lived in lowland rainforests.

“Although the Hainan gibbons’ preferred tropical trees grow mainly below 800 metres, they have been restricted to above 800 metres because there is not enough thick forest below,” says Dr Bosco Chan Pui-lok, head of Kadoorie Conservation China, a department of Hong Kong’s Kadoorie Farm and Botanic Garden that is assisting with conservation work in Hainan.

In Hainan, there are only six breeding females left. It’s not hard to imagine how a disease outbreak, typhoon or just a chance death could spell the end of the species
Dr Bosco Chan, head of Kadoorie Conservation China

And gibbons can be picky about mating. The remaining individuals could be so closely related that they are simply choosing not to mate with each other. Or perhaps human disturbance is stopping groups forming.

Thankfully, there has been a breakthrough. Until recently, wardens and researchers located the gibbons by listening for their dawn songs from posts high up in the Bawangling moun­tains. Solitary animals, however, don’t tend to sing. Last year, we trialled a technique widely used in bird surveys. We played a recording of a gibbon call in an area where no gibbons were thought to be. Amazingly, a male appeared in the treetops, drawn by the sound. Then a female showed up with a baby. This was a fourth, previously unknown social group.

We hope that call-playback might also be useful for locating the cryptic solitary gibbons, but we need to think carefully about doing this. Playing gibbon calls could affect the behaviour of the animals or stress them. Once a species drops to perilously low numbers, it can remain vulnerable to extinction even if the factors respon­sible for the initial population crash – in this case, deforest­ation and hunting – are removed. In Hainan, there are only six breeding females left. It’s not hard to imagine how a disease outbreak, typhoon or just a chance death could spell the end of the species. And with a population this small, the effects of inbreeding cannot be ignored. Any of these factors could push the Hainan gibbon into what conservation biologists call the “extinction vortex”.

Despite this, I believe we can save the world’s rarest ape. It’s not too late: the population seemed to hit a low of 13 in 2003 and has since grown, and two of the four groups at Bawangling formed in the past few years. But it’s not going to be easy. We need a close collaboration between reserve staff, who understand the local politics and logistics of working in Hainan, and international organisations that have experience with extremely threatened species. A top priority has to be reconnecting the forest fragments in Bawangling. Long term, this means planting trees. In the short term, artificial canopy bridges may encourage the gibbons to move between patches.

Work is already under way, with Kadoorie Conservation China having helped plant more than 83,000 trees, consisting of 51 species, that sustain the gibbons. It has also funded projects to study the ecology, population dynamics, potential habitat, habitat restoration and conservation management of the animals.

“I am very hopeful about the future of the Hainan gibbons,” says Chan. “When we first surveyed the area, we found only two groups of Hainan gibbons, now there are four groups, with over 25 gibbons. The number of known gibbons has more than doubled.

“The Hainan gibbons have the highest birth rates of gibbon species in the world, and all of their children are growing to adulthood.”

It is possible to bring species back from the very edge of existence. The Mauritius kestrel recovered from just four wild birds in the 70s and the Chatham Island black robin came back from five individuals in 1980. My hope is that we will one day be able to list the Hainan gibbon alongside these success stories and those lucky enough to visit the island will continue to hear the haunting dawn song of the gibbon.

The alternative – that it will only be remembered in stories told by old villagers – is a future we cannot allow.

Text: New Scientist
Sam Turvey is a conservation biologist at the Zoological Society of London

KADOORIE FARM COMES TO THE RESCUE IN CHINA AND LAOS
Kadoorie Farm and Botanic Garden (KFBG), established in 1956, is an education and conservation centre near Tai Po. Over the past two decades, it has undertaken projects outside Hong Kong, such as in mainland China and Laos.

Kadoorie Conservation China (KCC), a department of KFBG, was created in 1988 and runs conservation projects and education programmes in several mainland provinces. KCC’s species conservation projects include those that assist the Hainan gibbon, the oriental pied hornbill, the eld’s deer, the sika deer, box turtles, monitor lizards and freshwater fish, and involve efforts such as reforestation, building artificial nest boxes, conducting population surveys, relocating populations in danger and creating fish sanctuaries.

The department’s ecosystem conservation projects are located at the Yinggeling National Nature Reserve and the Exianling limestone forest, both in Hainan, and involve surveying flora and fauna and educating locals about the merits of conservation.

In Yunnan, KCC works in collaboration with the Gaoligongshan National Nature Reserve on the Sino-Myanmar border, home to the eastern hoolock gibbon, and in the Tongbiguan nature reserve. KCC also funds conservation initiatives for the north-Chinese leopard in Shanxi and the loris in south Yunnan.

Some of the department’s more unusual projects have included designing a wetland system to treat wastewater by filtering it with strainers and natural plants, painting murals in villages to promote nature appreciation and helping to set up no-catch zones to help fish populations recover.

In Laos, KFBG runs flora conservation projects that involve biodiversity surveys in remote areas and capacity building for the Biotechnology and Ecology Institute, of the Ministry of Science and Technology.

Additional reporting by Andrew Sheets