Gibbons are rare in modern-day China. All four species found in the country are threatened with extinction, and they live in only 11 prefectures in a small corner in southwestern China. One species, the Hainan gibbon, numbers only 23 to 25 individuals. The animals live in a tiny patch of forest in the Bawangling National Nature Reserve and may be the world’s rarest mammal. Two more species have completely disappeared in the last two decades.
If researchers want to prevent the extinction of China’s few remaining gibbons, it would help if they had data on gibbon populations from the past. But that kind of information is rare. Pre-modern China didn’t have a tradition of scientific publishing like European nations did. What they did have, though, were local “gazetteers,” documents that compiled economic, political, demographic and environmental data, including animal sightings. And these gazetteers were systematically collected from the Ming Dynasty onwards. They aren’t a perfect record of past gibbon populations — in part because they don’t say anything about individual species — but they may be a better record for gibbons than for many other animals, because the primates were said to have mythical or supernatural properties.
Samuel Turvey of the Zoological Society of London and colleagues collected 535 dated records of gibbons from 420 gazetteers published from the Ming Dynasty (1368-1644), Qing Dynasty (1644-1912) and Republican period (1912-1949). Turvey translated each record, and the team supplemented the records with historical data from the 20th century and modern-day distribution data. They then mapped out where gibbons lived over the last five centuries. They published their findings August 5 in the Proceedings of the Royal Society B.
Prior to 1600, gibbons could be found across much of central, southern and eastern China, the researchers found. But starting in 1600, the animals’ range began to contract, and after 1850, populations were disappearing quickly. By 1900, gibbons had disappeared from 57.5 percent of the regions in which they were once found, and by 1950, they were gone from 84.4 percent of those places.
The pattern of disappearance matches the history of the expansion and migration of China’s human population, the team notes. “Gibbon populations therefore appear to have been highly vulnerable to the wavefront of this internal Chinese human population expansion, which would probably have included combined increases in both forest loss and hunting,” the scientists write. The findings are also consistent with the accounts of European naturalists, who in the 18th and 19th centuries noted that gibbons were rare.
The researchers found a couple of patterns that could have implications for China’s modern-day gibbons. First, gibbon populations tended to persist at higher elevations, and that is where all remaining populations are. Those elevations may be at the limit of where gibbons can successfully live, and it may represent habitat that isn’t so great for the animals. That could explain why Chinese gibbons exhibit behaviors, such as having very large home ranges, that are unusual for gibbons elsewhere in Asia.
The data also indicated that a population that becomes isolated is at risk — extinction tends to follow within just 40 years. That could be particularly bad news for the Hainan gibbon. This extremely isolated population has been known since 1980. The clock is ticking. If this species is to survive, identifying effective conservation measures must be a high priority, the researchers warn.