Living on the edge: Forest edge effects on microclimate and terrestrial mammal activity in disturbed lowland forest in Sumatra, Indonesia

Species-environment relationships are often studied at large spatial scales, but effective conservation requires an understanding of local scale environmental drivers and pressures. Widespread degradation and fragmentation of forests has greatly increased the proportion of tropical mammals’ habitat that is impacted by edge effects. Edge effects include greater exposure to anthropogenic disturbance as well as abiotic changes that will synergistically influence how populations can cope with climate change. We investigated relationships between distance to the forest edge, forest structure, microclimate, and terrestrial mammal detections in a selectively logged forest at the boundary of the Gunung Leuser National Park in Sumatra, Indonesia. We collected mammal detection data from motion-activated camera traps, microclimate data from automated climate data loggers, and forest structure data from vegetation plots. Daily mean and maximum temperatures significantly decreased with distance from the forest edge, whilst tree height and minimum temperatures increased. Mammal diversity was lower at the forest edge compared to the interior. Mammals were detected less frequently at the forest edge, although this relationship differed between mammal Orders. Mammal detections were best explained by temperature, tree height and tree diameter at breast height. These results demonstrate that abiotic changes in forests brought on by edge effects have negative impacts on mammals, but their impacts vary between mammal taxa, due to differing sensitivities to human disturbance. These data highlight the importance of considering local scale environmental drivers in determining species-environment relationships to identify key habitat features, such as microclimate refuges, that should be prioritised in ecosystem management.