Logging, Forest Structure and Primate Group Densities in North Sumatra, Indonesia
Start date: 2 December 2015
Tropical forests contain a substantial portion of global biodiversity, and provide a wide range of ecosystem services. Anthropogenic activities alter the physical structure of forests and thus impact arboreal primates through reduced mobility, availability of food and suitable sleeping sites. This study investigated the structure of disturbed forest at Sikundur, North Sumatra, Indonesia and the group density of an arboreal primate, Presbytis thomasi, in order to identify links between forest structure and primate density. Quantitative data was collected on forest structure from line transects and plots and compared between three land units: alluvial, hills and plains. Group densities of Presbytis thomasi were estimated using line transects and vocal arrays. Prior to this study, vocal arrays had not been applied to P. thomasi, however this method proved to be more effective than distance sampling along line transects, especially in disturbed forest where visibility is poor, and primates are unhabituated. Top height and the proportion of large, emergent trees was consistently low throughout the study site due to selective logging in the 1970s and 80s. Illegal logging remains a regular occurrence in the area. Overall species density was XX (SECR method of analyses) and XX (Brockelman method). In relation to tree characteristics, tree diameter at breast height was greatest in the alluvial area and density of trees above 25meters was lowest in the plains land unit; while average tree height and density did not differ between the three land units measured at this location. P. thomasi densities were greatest in the hills land unit. This study forms part of the beginning of a long term collaborative project entitled LEAP, Landscape Ecology and Primatology, investigating the impacts of deforestation and habitat degradation in tropical ecosystems.