Decades of financial improvement, together with logging and deforestation, had lowered their habitat by greater than half.
What major forest remained was additionally fragmented, additional hemming within the tailless apes, which journey solely above floor.
But the huge mudslides unleashed by tremendous hurricane Rammasun made issues worse, gouging 15-metre large gullies into the mountainous forest and successfully chopping off their treetop highways.
“Canopy connectivity is critical for gibbons as they are strictly arboreal,” lead writer Bosco Pui Lok Chan, head of the Kadoorie Farm and Botanic Garden in Hong Kong‘s New Territories, informed AFP.
“Forest fragmentation thus presents a major conservation challenge for gibbons.”
After the hurricane, Chan and his crew — charged with defending the gibbons, only some dozen of which stay within the wild — noticed that that they had hassle crossing these new gaps within the forest.
And after they did, “they took very risky routes involving a lot of long jumps and high falls among the few surviving trees,” he mentioned.
Then Chan had a light-bulb second.
“We constructed a two-pronged canopy rope bridge across the damaged arboreal highway,” he mentioned.
The “bridge” consisted of two parallel ropes tied at both finish to bushes.
The conservationists additionally arrange movement cameras to document any motion on or throughout the ropes.
The group of 9 gibbons most affected by this specific gash within the forest did not avail themselves of the lifeline straight away.
Indeed, solely 176 days later did the cameras seize the primary picture of a gibbon on the ropes.
After that first crossing, nonetheless, others rapidly adopted go well with.
Some strode throughout the mountaineering-grade ropes like tight-rope walkers, whereas others moved beneath, swinging arm to arm.
Gibbons shifting throughout a forest cover have been clocked at over 50 kilometres (30 miles) an hour utilizing this technique.
Another favoured approach was strolling throughout one rope, whereas holding on to the second overhead.
Over the 470 days of monitoring, the researchers collected greater than 200 footage and 50 movies of the acrobatic apes in motion.
Chan described the rope bridges as a “short-term solution”.
“Reforestation with native tree species should be the priority for restoring forest connectivity,” he mentioned.
But his stop-gap measure nonetheless has “significant conservation implications for other gibbon species,” he added.
There are 20 recognized gibbon species, all in Asia. Most are both “endangered” or “critically endangered” — the final step earlier than “extinct in the wild” — on the IUCN’s Red List of endangered species.
The Hainan gibbon — Nomascus hainanus — is endemic the Chinese island, and now discovered solely within the Hainan Bawangling National Nature Reserve.
Their inhabitants was estimated at 2,000 people within the 1950s, however through the 1970s their numbers plunged to single digits, based on the researchers.
Adult males are jet black with a furry crest, whereas females are golden yellow with a black crown.
Most gibbons are monogamous, however N. hainanus dwell in households with one male, two females and immature offspring.
The are recognized to sing in duets at daybreak, most likely to mark their territory and improve bonding, earlier analysis has proven.