Status of a second viable population of the Critically Endangered Delacour's langur in Viet Nam

Abstract

One of the three Critically Endangered and endemic primate species in Viet Nam, Delacour's langur Trachypithecus delacouri, is restricted to the north of the country. The largest remaining population is in Van Long Nature Reserve, Ninh Binh Province, and the second largest is in nearby Kim Bang Protection Forest, Ha Nam Province, with other populations believed to be too small for recovery. The population in Van Long has been well studied but the status of that of Kim Bang has not previously been adequately evaluated. To address this, a survey was conducted during 10 August–7 October 2018. In total, we recorded 13 groups comprising a total of at least 73 individuals, almost doubling the highest number reported in previous studies. We documented six new groups in Lien Son and Ba Sao communes in Kim Bang. Our findings indicate there is a high likelihood that Delacour's langur population in Kim Bang will recover and could be important for the long-term conservation of this Critically Endangered species. However, immediate and appropriate conservation measures need to be implemented to protect the population from major anthropogenic threats, namely poaching and habitat destruction, detected during our survey.

Advancing conservation of threatened primates

“…We cannot develop conservation plans for threatened primates without accurate population assessments (Rylands et al, 2020). These novel studies, together with more traditional research—such as for the Endangered ring-tailed lemur Lemur catta in Madagascar (Randrianjaka et al, 2024), the Endangered golden monkey Cercopithecus mitis kandti in Rwanda (Tuyisingize et al, 2023), the Critically Endangered Vieira's titi monkey Plecturocebus vieirai in Brazil (Costa-Araújo et al, 2022), and the Critically Endangered Delacour's langur Trachypithecus delacouri in Viet Nam (Nguyen et al, 2022)—all deal with surveys and the provision of essential baseline data.…”