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PARIS: Hainan gibbons, the rarest primates on Earth, were already on the brink of extinction in 2014 when the most powerful storm to hit the coast of China in half a century devastated their oasis on the island.
Decades of economic development, along with logging and deforestation, had reduced their habitat by more than half.
The remaining primary forest was also fragmented, further closed off in the tailless apes, which travel exclusively above ground.
But the massive landslides unleashed by super typhoon Rammasun made matters worse, opening 15-meter-wide gullies in the mountainous forest and effectively cutting off their roads in the treetops.
There are 20 species of gibbons identified in Asia. Most are “endangered” or “critically endangered.” (Photo: AFP)
“Canopy connectivity is critical for gibbons as they are strictly arboreal,” lead author Bosco Pui Lok Chan, director of the Kadoorie Farm and Botanical Garden in Hong Kong New Territories, told AFP.
“The fragmentation of forests therefore presents a major conservation challenge for gibbons.”
Not only does it limit their ability to forage for food, it can interfere with the search for a mate and make them more vulnerable to predators.
BULB MOMENT
After the typhoon, Chan and his colleagues noticed while monitoring the gibbons, of which only a few dozen remain in the jungle on the Chinese island of Hainan, that they had trouble crossing these new holes in the forest.
And when they did, “they took very risky routes that involved a lot of long jumps and high drops among the few surviving trees,” he said.
Then Chan had a lightbulb moment.
“We built a double-ended canopy rope bridge across the damaged tree road,” he said.
The “bridge” consisted of two parallel ropes tied at each end to trees.
Hainan’s gibbon population was estimated at 2,000 individuals in the 1950s, but during the 1970s their numbers dropped to single digits. (Image: AFP / John Saeki)
Conservationists also installed motion cameras to record any movement on or through the ropes.
The group of nine gibbons most affected by this particular wound in the forest did not immediately use their lifeline.
In fact, just 176 days later, cameras captured the first image of a gibbon against the ropes.
However, after that first crossing, others quickly followed suit.
DUETS AT DAWN
Some strode across the mountaineering level ropes like tightrope walkers, while others moved underneath, swinging from arm to arm.
Gibbons moving through the canopy of a forest have been recorded at over 50 km / h using this method.
Another preferred technique was to walk on one rope, while holding the second rope above the head.
During the 470 days of follow-up, the researchers collected more than 200 photos and 50 videos of the acrobatic apes in action.
Chan described rope bridges as a “short-term solution.”
Most gibbons are monogamous, but N. hainanus lives in families with one male, two females, and immature offspring. (Image: AFP / Jonathan Jacobsen, Paz Pizarro)
“Reforestation with native tree species should be the priority to restore forest connectivity,” he said.
But his interim measure still has “important conservation implications for other gibbon species,” he added.
There are 20 species of gibbons identified, all in Asia. Most are “endangered” or “critically endangered” – the last step before “going extinct in the wild” – on the IUCN Red List of Endangered Species.
The Hainan gibbon, Nomascus hainanus, is endemic to the Chinese island and is now only found in the Hainan Bawangling National Nature Reserve.
Their population was estimated at 2,000 individuals in the 1950s, but during the 1970s their numbers dropped to single digits, according to the researchers.
Adult males are jet black with a hairy crest, while females are golden yellow with a black crown.
Most gibbons are monogamous, but N. hainanus lives in families with one male, two females, and immature offspring.
They have been known to sing a duet at dawn, probably to mark their territory and enhance bonding, previous research has shown.
