Effects of anthropogenic disturbance on group densities of Thomas' langurs (Presbytis thomasi) within a lowland tropical forest, north Sumatra. Issue 2 (27th November 2022)

• Record Type: Journal Article
• Authors: Hankinson, Emma; Korstjens, Amanda H.; Hill, Ross A.; Wich, Serge A.; Slater, Helen D.; Abdullah, Abdullah; Supradi, Supradi; Marsh, Christopher D.; Nijman, Vincent
• Is Part Of: Ecological research. Volume 38:Issue 2(2023)
• Page Start: 293
• Page End: 305
• Publication Date: 2022-11-27
• Subjects: acoustic surveys -- anthropogenic disturbance -- leaf monkeys -- primates -- Thomas' langur; Ecology -- Periodicals; Ecology -- Japan -- Periodicals; Écologie; Japon; Ecology; Japan; Ressource Internet (Descripteur de forme); Périodique électronique (Descripteur de forme); Periodicals; 577.05
• DOI: 10.1111/1440-1703.12373
• Languages: English
• ISSNs: 0912-3814

Abstract

Abstract: Ecosystems around the globe are facing irreversible impacts due to climate change, habitat destruction, hunting, and an ever‐increasing human population. Estimating densities of species across their geographical range helps us to understand natural variation and anthropogenic effects on species densities and to assess the effectiveness of existing conservation measures. Various methods have been used to produce accurate and precise population density estimates, each with associated limitations. Acoustic surveys for species producing loud calls have become common due to their ease of use, low cost, and reduced timescale. Relative to many other mammal taxa, primate species have been studied extensively, producing a wealth of data on socioecology and behavior, but for most species, density estimates over large geographical ranges are still lacking. We used an acoustic spatial capture–recapture model to estimate group density of unhabituated Thomas' langurs ( Presbytis thomasi ), a primate endemic to the Indonesian island of Sumatra, over a 60 km 2 area of lowland dipterocarp forest. We then assessed if vegetation structure and distance from human habitation affected density estimates. Estimates of group density differed almost threefold between survey locations (from 2.79 to 8.08 groups/km 2 ); there was no clear relationship with forest structure, but there was a significantly positive relationship between group density and distance from human habitation, with an increase of 0.38 groups/km 2 for every km of distance. Although large‐scale logging within the Sikundur region ceased ~30 years ago, the impacts of logging continue to have detrimental effects on the species within the area. Abstract : Using acoustic methods to estimate group densities of Thomas langurs over a large area in relation to anthropogenic disturbance. Thomas langur densities are lacking in many areas of their range due to problems associated with studying unhabituated individuals. Anthropogenic disturbance on group densities seems to have a time lag in identifying these effects.