Unique study aids efforts to protect gibbons

Gender confusion

Xinping is now more than 7 years old, close to sexual maturity. But it's still hard to determine its gender, which can usually be easily recognized by the color of the fur. However, the coats of western black crested gibbons change color during their lives, according to Jiang.

"Their fur is usually dark brown or black after birth and it turns yellow at the age of 2. A final change will come when they are 8 years old. The fur of females remains yellow and the males' fur turns black," he said.

More confusingly, irrespective of gender, juvenile western black crested gibbons have a "fake" penis, which gradually disappears if the carrier is female.

Jiang said studies are ongoing, as there are many special characteristics that need to be determined.

"Before we get an answer, our prime task is to protect the apes from extinction, so our younger generation will have a chance to see the species and continue this research," he said.

Heading toward extinction?

China is home to six subspecies of gibbon: the eastern black crested; the western black crested; the Skywalker hoolock; the Hainan; the Lar; and the Northern white-cheeked.

The first four are listed as "critically endangered" on the Red List of the International Union for Conservation of Nature, while the others may now be extinct.

Black crested gibbon (western and eastern)

It is found in China, Laos and Vietnam. However, China has the largest population, with only small groups found in the other countries.

Population estimates in China range from about 270 to 300 groups, with the most important subpopulations residing in the Wuliang Mountains and the Ailao Mountains in Yunnan province.

Hainan gibbon

In the late 1950s, the population was estimated to be about 2,000 individuals. By 1989, that was thought to have fallen to a single relict population-the remnants of a larger unit-of 21 gibbons in four groups.

At present, there are more than 25 individuals, but the exact number cannot be ascertained because of the difficulty of tracking dispersed juveniles.

Skywalker hoolock gibbon

In China, the population is estimated to be approximately 200 individuals in nine small groups. In Myanmar, estimates range between 10,000 and 50,000 individuals, representing at least 98 percent of the global population.

Lar gibbon

In the 1960s, there were estimated to be 200 individuals on both sides of the Nangun River in Yunnan. In 1988, the date of the last sighting, it was estimated that there were less than 10 groups.

Meanwhile, in 1992, the date of the last survey, the authors did not find any direct evidence of the species' persistence but estimated that three groups may remain, with about 10 individuals in total. Recent data suggest that this species has died out in China.

Northern white-cheeked gibbon

It may now be extinct in China. A series of surveys documented its decline from about 1,000 individuals in the 1960s to probable extinction. The most recent surveys in the Mengla and Shangyong Nature Reserve, Yunnan, in 2008 and 2011, determined that the species is either extinct or functionally extinct in China.

SOURCE: RED LIST OF THE INTERNATIONAL UNION FOR CONSERVATION OF NATURE