A monkey bridge to save the gibbons of Hainan

II just had to think about it. The expression, attributed to Christopher Columbus presenting his famous egg, has crossed the centuries. Through an extremely simple experience and a concise sentence, the navigator silenced the smart kids for whom discovering America was not so complicated. A Hong Kong team has just brought the maxim up to date. To save monkeys threatened with short-term extinction, they built … a monkey bridge. And it works ! The anecdote will probably never make it into the history books, but the experience figures prominently in the October 14 issue of the review. Scientific Reports.

The gibbons of Hainan (Nomascus hainanus) are considered the most endangered primate species in the world. Nearly 2,000 sixty years ago, there were only 13 in 2003, gathered on this island in southern China. The extreme attention paid to the Bawangling National Reserve prevented their immediate disappearance. It even made it possible to approach the threshold of thirty individuals when in 2014, typhoon Rammasun hit the archipelago. The worst hurricane recorded in the region since 1949, with torrential rains and major landslides. “Holes have appeared in the canopy, up to 30 meters wide”, said Bosco Chan, head of the conservation department at the Hong Kong Botanical Garden. Almost impassable abysses for the 8 individuals of group C. “Females and juveniles, in particular, remained blocked”, tells the scientist.

The foresters therefore replanted young trees. But would the gibbons hold out for the five years needed to restore a canopy worthy of the name? Bosco Chan’s team, which has followed the species since the 1980s, decided in 2015 to experiment with a particularly simple device: two ropes, stretched one above the other between trees more than 15 meters. The most basic version of what we call a “bridge of monkeys”.

Three births

Were the primates going to adopt the facility? Artificial bridges have already been built to allow monkeys to cross roads or rivers. But not in the midst of forests, let alone in response to a natural disaster. “We had high hopes, they are very intelligent animals, but it took a lot longer than expected”, admits the researcher.

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