Gibbons hanging on in Hainan

HAINAN Island, which I visited a few years ago, is a crowded place, writes Richard Collins

Gibbons hanging on in Hainan

Almost 9m people live in an area the size of Munster.

The tropical waters of the South China Sea teem with exotic fish, but the island’s chief claim to fame is a forest nature reserve which supports one of the world’s rarest mammals, the black-crested gibbon. The outlook for this critically endangered species is grim but a recent find offers a glimmer of hope.

According to a review in Science News, China once had six species of gibbon. Two of them disappeared in the last 20 years. The remaining four are threatened with extinction. The black-crested species, the most endangered of all, was found throughout much of southern China before habitat destruction and poaching brought it to death’s door. Half a century ago, there were about 2,000 left. Numbers continued to fall until only about 25 animals remained; three family groups and a few ‘loners’, solitary individuals living on their own.

Gibbons are apes, members of an old world primate family. Apes differ from monkeys in being tail-less. Their flexible shoulder-joints and very long arms enable tree-dwelling members of the tribe to travel through forests, swinging Tarzan-like from tree to tree.

Gorillas, orangutans, chimps and humans constitute the great ape group. We had a common ancestor with our nearest relatives, the chimps, between 6m and 7m years ago. The gibbons, so-called lesser apes, are found in South-east Asia. Europe’s only primate, apart from ourselves, is known as the ‘Barbary ape’. It’s not an ape but a species of monkey introduced to Gibraltar from north Africa in the 17th century.

The gibbon evolutionary line diverged from the one which led to the great apes over 16m years ago. Like us, and unlike most other primates, gibbons form strong pair-bonds. Since they don’t indulge in winner-takes-all contests for access to females, males don’t need to be huge; the sexes don’t differ much in size or appearance. No silverbacks here.

Sixteen species of gibbon survive. The largest of them, the siamang, has the distinction of being Dublin Zoo’s noisiest animal; inflated air sacks in their throats help siamangs broadcast their messages to visitors in the Phoenix Park. Fota Wildlife Park has siamangs and two other gibbon species. It is one of a handful of zoos to have successfully bred the smallest member of the family, the agile gibbon. A mating pair of these expert climbers has lived in the park since the 1990s. The lar gibbon, another aerial acrobat, has also bred in Fota.

Attempts to breed the black-crested gibbon in zoos have unfortunately been unsuccessful; the survival of this critically endangered species now depends entirely on the tiny wild population on Hainan Island. These gibbons feed on leaves fruit and insects; there is sufficient in the habitat to allow the population expand. The single baby is dependent on its mother for about a year and a half. Such a slow reproductive rate makes it difficult for gibbons to increase their numbers.

But there’s some good news. A team of gibbon experts and national park staff, led by Jessica Bryant of the Zoological Society of London, carried out a search of the forest recently, hoping to find one or two solitary animals not previously recorded. The singing of gibbons has helped hasten their decline; poachers can track them by following the sound.

A solitary animal won’t perform unless it thinks that there are other gibbons in the vicinity, so the scientists played recordings of gibbon calls hoping for a response. To their delight, they discovered a previously unknown breeding pair with a baby. There are now 28 Hainan gibbons in four breeding groups. The find may not seem significant but, with a species as critically endangered as this, it’s an important development.

  • Sarah Zielinski. Gibbons have been disappearing from China for centuries. Science News. August 2015.

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