By Carolyn Cowan
The morning song of gibbons, with its accelerating, bubbling crescendo, is arguably one of the most enthralling sounds of the tropical forests of Southeast Asia. For many, it’s a sound that signifies the vitality of the forest ecosystem — if there are gibbons, there must be fruit, and therefore likely a plethora of other fruit-eating species. But for primatologists, the gibbon’s song contains telltale clues that help them identify which of the world’s 20 species is about.
This acoustic approach was recently adopted by a team of specialists in Myanmar, resulting in the discovery of previously unknown populations of Skywalker hoolock gibbons (Hoolock tianxing), an incredibly rare species of the small apes only described by scientists as recently as 2017.
The finding, documented in a new study published in the International Journal of Primatology, is first time Skywalker hoolock gibbons have been confirmed in Myanmar, and expands the endangered species’ range beyond the borders of China where a tiny population of fewer than 200 individuals represents the only other known record of the species on Earth.
“This is a very important discovery,” said study co-author Pengfei Fan, a researcher at Sun Yat-Sen University in China. “Considering the very small population in China … Myanmar plays the most important role in conserving this species. I hope resources will be invested to protect [it] and its habitat.”
Fan was among the team of researchers who first described Skywalker hoolock gibbons as distinct from their close relatives, the eastern hoolock gibbon (H. leuconedys), in southwestern China in 2017. Skywalkers are named in part for the Chinese characters in their scientific name, which translate to “heaven’s movement” and also as a nod to the famous film franchise, “Star Wars,” of which the 2017 team are fans.
Since gibbon songs can carry across the forest landscape for more than 1 kilometer (0.6 miles), the Myanmar survey team, led by researchers from Fauna & Flora and Nature Conservation Society Myanmar, listened for gibbons on higher ground, mainly along ridges and hillsides, and deployed triangulation methods to pinpoint the location of groups of gibbon troops and estimate their numbers.
Once they had a gibbon troop within their sight, the researchers took photographs to confirm visual characteristics of the species; Skywalkers typically have thinner eyebrows than other hoolock gibbons, and also sport a black or brown beard, rather than a white one.
The researchers then scoured the ground for chewed remains of fruits and other plants and used a specially designed genetic analysis kit developed by the One Health Institute at the University California, Davis, in the U.S. to identify the gibbons to species level.
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