Hainan Gibbons

Artificial rope bridges prevent rare primates from being threatened with extinction

By Clare Wilson

An adult female Hainan Gibbon (golden yellow) with an immature individual (black)

Kadoorie Farm and Botanical Garden

With a population that dropped to just 25 a few years ago, every Hainan gibbon counts. When a landslide on the Chinese island of Hainan in 2014 forced the last surviving members of the world's most endangered primate species to make death-defying leaps over a gap in the forest canopy, conservationists helped them by stringing ropes between the trees.

The plan worked. Although it took the gibbons (Nomascus hainanus) six months to get used to the idea, most of them eventually used the rope bridges to cross the 15-meter gap, either swinging, crawling upside down, or sometimes balancing like tightrope walkers. Only the larger males didn't need the ropes.

Gibbons are very reluctant to get down. After the landslide, this group reached fruit trees by hurling themselves over the large gap over a rocky ground up to 30 meters deep. Although the researchers didn't see any accidents, they thought a fall would be fatal. "It was pretty scary to see – my heart just popped out of my throat," says Bosco Chan of Kadoorie Farm & Botanic Garden in Hong Kong.

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Mothers had to make the jump while their baby was holding on. "If the mother carrying the child falls, that would have been two out of 25," says Chan.

Today there are believed to be around 30 gibbons on the island. Trees in the dangerous area have now grown back, but according to Chan, rope bridges are proving useful in helping other primates bridge gaps between fragmented habitats.

Journal reference: Scientific Reports, DOI: 10.1038 / s41598-020-72641-z

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