Tigers, terrain, and human settlement influence the occupancy of leopards (Panthera pardus) in southwestern Tarai, Nepal

Maintaining a healthy population of common leopards, a highly adaptive felid, requires updated information on their spatial occurrence. In Nepal's Tarai region, leopards coexist with tigers, which is a well-studied felid throughout its range. However, knowledge is very scarce on the occupancy of leopards and its influencing factors. We carried out a camera-trap occupancy survey in southwestern tarai particularly in Shuklaphanta National Park, Nepal, to assess habitat use by leopards from December 2022 to January 2023. The naïve occupancy was 0.51. The model-averaged occupancy estimate for the leopard was 74 %. The best fitting model included tiger presence as an explanatory covariate for the detection component, i.e., detection probability of leopard was lower where tigers were present. The occupancy component of the best-fitting model included distance to human settlement and higher in terrain ruggedness. Leopard occupancy was higher closer to human settlement and higher in rugged terrain. At a time when Nepal has achieved its tiger conservation targets, efforts are required to maintain adequate prey biomass to minimize fatal encounters between tigers and leopards and displacement of leopards in fringe areas where villagers might kill them in retaliation of livestock killing. Long-term monitoring is required to improve understanding of the interaction between leopards, tigers, and humans in the Tarai region of Nepal.

Methods
A comprehensive tiger and prey base monitoring was conducted during December 2022 and January 2023 in the entire 305 km2 of ShNP based on the tiger monitoring protocol of Nepal 2017 (DNPWC, 2017). The survey employed a total of 92 survey grid cells (see Figure 1), each measuring 4 km2 (2 km × 2 km). Panthera V5 and V6 automated cameras were systematically placed in pairs in strategic locations preferably on dirt road, fire lines, dry riverbeds, and animal trails to maximize the detectability of tiger (Karanth et al., 2011). The camera traps were positioned between 45 cm and 60 cm above the ground, and they were deployed for 15-19 nights in each of the grid cells. Each camera trap was set to take three pictures per trigger with no delay (FAP mode) using white flash. These cameras were checked every morning to observe and document any tigers and leopards or other species captured during the previous night. The survey was targeted for the tiger monitoring but as they used similar path, we extracted the data of leopard from the same camera locations.