The Fauna & Flora Organization in Vietnam has utilized voice biometric technology to confirm that the population of the Northern White-cheeked Gibbon distributed in a small forest along the Vietnam-China border is 74 individuals, rather than the previously estimated 120.
This study was published in the journal Nature on January 3, 2024. The survey re-evaluated the Northern White-cheeked Gibbon population in 2021, a rare primate species that was once thought to be extinct, conducted by the Fauna & Flora Organization in Vietnam. This marks the first time the research team has applied the “voice biometric technique”, using recording devices to capture gibbon songs and accurately identify the calls of each individual.
The Northern White-cheeked Gibbon (scientific name: Nomascus nasutus) is the second rarest gibbon species in the world and is listed among the 25 most endangered primate species globally. Currently, this species is only found in the Northern White-cheeked Gibbon Species and Habitat Conservation Area in Trùng Khánh District, Cao Bằng Province and the adjacent forest region within the Bang Luong National Nature Reserve in Guangxi, China.
A male Northern White-cheeked Gibbon with a black body and a tuft of hair on top of its head. (Photo: Nguyen Duc Tho/Fauna & Flora).
According to scientists, each gibbon’s song has distinct characteristics, especially among males. The team used 29 listening points to monitor and record gibbon groups singing “high-pitched” from before sunrise until noon. Thermal drones were also employed to specifically locate groups and provide more accurate individual counts. This activity took place from late October to early November 2021, resulting in the discovery of 74 individuals.
Previously, monitoring methods relied on binoculars and cameras, which might have inflated the estimated population to 120 individuals. The research team also faced challenges due to the treacherous, steep limestone terrain, making it nearly impossible to access quickly as the gibbons moved rapidly through the dense canopy.
Dr. Oliver Wearn, a senior expert and team leader, stated that the Northern White-cheeked Gibbons are “noisy singers.” They primarily assert their territory through song, which can be heard from kilometers away. According to Dr. Oliver, each mature male gibbon has its own unique song, and the team leveraged this characteristic for their survey.
“The voice biometric method allows for a more accurate overall picture of the species population, facilitating the study of populations without human impact on their natural behavior,” Dr. Oliver said.
Nguyễn Đức Thọ, project manager for the Northern White-cheeked Gibbon Conservation Project at Fauna & Flora in Vietnam, noted that utilizing new technology for population monitoring increases accuracy and provides more reliable data. This technology also facilitates a better understanding of this unique primate species.
The Northern White-cheeked Gibbons live in small groups in the trees. (Video: GCT team/Fauna & Flora).
This species of gibbon was recorded in Vietnam as early as 1884, and in 1965, three specimens were collected in Trùng Khánh District, Cao Bằng Province. Subsequently, the species was considered extinct until it was rediscovered by the Fauna & Flora Organization in 2002. At that time, scientists found a population of about 26 individuals remaining in a small forest within two communes, Phong Nậm and Ngọc Khê, in Trùng Khánh District. To conserve this exceptionally rare primate species, Cao Bằng Province established the Northern White-cheeked Gibbon Conservation Project, operational since March 2004, and created the Northern White-cheeked Gibbon Species and Habitat Conservation Area in 2007.
