As a biodiversity hotspot in Asia, Viet Nam harbours about 25 primate taxa, the highest number among all mainland South-east Asian countries. Yet at least 20 of these are threatened with extinction, and overhunting and habitat destruction continue to be the main threats to primate populations across the country.

Delacour’s langur Trachypithecus delacouri, a primate that inhabits limestone habitats, previously ranged over an area of c. 5,000 km2 in northern Viet Nam. As the species was extirpated from much of its range, it has been consistently ranked as one of the most threatened primates. The current total population is estimated to be c. 300 individuals, with the largest remaining population in Van Long Nature Reserve, and the second largest population in the nearby Kim Bang area. The Delacour’s langurs in Van Long Nature Reserve were formerly considered the only viable population, with populations considered too small for recovery. Field surveys from the 1990s to 2016 by various organizations revealed several langur groups, with a total of c. 40 individuals, in Kim Bang protection forest in Ha Nam Province. All previous surveys, however, had only covered less than 50% of the forest in Kim Bang.

Delacour’s langur recorded during our field survey. Photo: Anh Tuan Nguyen

Our recent comprehensive field survey on Kim Bang, with the support of local people and authorities, from 10 August to 7 October 2018 recorded 13 groups and a total of at least 73 individuals, including six new groups. Our results indicate that Delacour’s langur have a high potential of population recovery in Kim Bang, and thus could play an important role in the long-term conservation of this Critically Endangered species.

Our findings provide welcome positive news for conservation in the Viet Nam, which has witnessed the serious decline of threatened primates and other species over the past few decades. Although the new population is still facing pressures from poaching and habitat degradation, particularly as a result of limestone quarrying, it could potentially recover if appropriate conservation measures are implemented immediately, as signs of recruitment, with several new infants, have been recorded. In 2020, recognizing the urgency of the situation, prominent international and national conservation organizations, including Fauna & Flora International, WWF–Vietnam, IUCN Primate Specialist Group, Central Institute for Natural Resources and Environmental Studies, and Center for Nature Conservation and Development, sent a request to the Prime Minister of Viet Nam to designate Kim Bang Forest as a new Species and Habitat Conservation Area.

A limestone mining site, immediately adjacent to a location where we recorded Delacour’s langur, in Kim Bang. Photo: Anh Tuan Nguyen)

Conserving the last remaining populations of the Delacour’s langur requires a great synergy of appropriate actions: better patrols and snare removals, active participation of local communities, improved protected area governance, and reduced habitat loss and degradation among others. These actions are not achievable by one organization, and thus the effective cooperation between different institutions, sectors, and stakeholders is urgently needed for the survival of the langurs.

The article Status of a second viable population of the Critically Endangered Delacour’s langur in Kim Bang District, Ha Nam Province, Viet Nam is available in Oryx—The International Journal of Conservation.

Anh Tuan Nguyen is a researcher and lecturer at University of Science, VNU Hanoi, Viet Nam. His research focuses on the biodiversity, biogeography, evolution and ecology of South-east Asian mammals, especially threatened species. He has also been working on integrating data from different methods, ranging from conventional field surveys and camera trapping, to phylogenetics, remote sensing, and modelling to reveal hidden patterns in the ecology and life history of rare and elusive taxa.