Ecological Determinants of Malabar Slender Loris (Loris lydekkerianus malabaricus, Cabrera 1908) Occupancy and Abundance in Aralam Wildlife Sanctuary, Western Ghats, India

Precise knowledge of a species’ habitat requirements is essential for its conservation. Very little information exists on the habitat requirements of the Malabar slender loris (Loris lydekkerianus malabaricus), a nocturnal primate, making it difficult to formulate conservation action plans. The goal of this study was to evaluate the ecological determinants of t he Malabar slender loris at the Aralam Wildlife Sanctuary, Kerala, India. We conducted surveys in a 1-km2 area in the southwest end of the sanctuary. We overlaid the study site with 1-ha grids and selected 83 grids for sampling. We surveyed each grid on five consecutive nights for the presence and abundance of lorises. We measured tree species richness, basal area, mean tree height, percentage shrub cover, percentage climber cover, climber species richness, percentage canopy cover, tree felling and branch lopping, paths, and the time taken to walk the trail. We built 19 models for occupancy and 17 models for abundance using PRESENCE 12.9. We detected 69 lorises in total in a 57.05-km walk with an encounter rate of 1.33 ± 0.21 SE individuals/km. The detection probability was 0.25 ± 0.04 SE for occupancy, and 0.13 ± 0.04 SE for abundance. The naive occupancy estimate for loris was 0.48, but the occupancy estimate of the top model with covariates was 0.67 ± 0.12 SE. The estimate of abundance (λ) was 2.40 ± 1.04 SE per grid cell. Basal area, species richness of the trees, and tree felling and branch lopping were the major positive determinants of loris occupancy and abundance. In contrast, the percentage climber cover negatively influenced occupancy and abundance. This suggests that climbers do not provide a complete platform for the lorises to move, while tree species richness and basal area reflect a greater number of trees that provide more connectivity than climbers. Detailed investigations using the methods we employed can be undertaken throughout the range of this species to determine occupancy and formulate conservation and management plans.