The applicability of camera trap data to monitor the cryptic Indian pangolin (Manus crassicaudata) populations: A survey from a tropical lowland rainforest in Southwest Sri Lanka

Abstract

The habitat occupancy, abundance, and population density of Indian pangolin ( Manis crassicaudata ) are poorly understood owing to their nocturnal and cryptic behaviors. This study presents the results of the first comprehensive study on the habitat occupancy, abundance, and population estimation of Indian pangolins using camera trap data in a tropical lowland rainforest habitat in the southwest of Sri Lanka. We conducted a camera trap survey using eight camera traps to sample the study site by partitioning it into 72 grid cells of 500 m x 500 m size. Traps were moved to new locations every 7 days. Data from 4480 camera trap nights at 640 locations in the 2000ha-Yagirala Forest Reserve were analyzed. The two main habitat types in the forest; Pine dominated forest (200 ha) and natural forest (1800ha) yielded 20 and 35 successful captures. A mean capture rate of 35.71 and 6.94 was recorded from the Pine forest and the natural forest. We further demonstrated the applicability of using camera trap data to estimate the population density of pangolins by fitting a Binomial-Poisson mixture model for a single visit capture data. All photographs of Indian pangolin were recorded between 7.00.00 pm and 6.00 am, with the highest frequency of photographs captured between 4.00 am, and 5.00 am (n = 10), followed by 8.00 pm and 9.00 pm (n = 08). The survey further provided exciting insights into burrow usage, possible nomadic behavior, and indirect interactions with sympatric mammals in the habitat. The implications for long-term monitoring and conservation are further discussed.