Dynamic occupancy modelling of Asian elephants (Elephas maximus) reveals increasing landscape use in Nepal

Abstract

Large mammals with general habitat needs can persist throughout mixed used landscapes, however, increasing human threats often restrict them to protected areas. Conservation efforts, especially for reducing conflicts with humans, can enhance tolerance of species like Asian elephants (Elephas maximus) in human-dominated landscapes. Here, we examine how elephant use of the Chure Terai Madhesh Landscape (CTML) covering the entire elephant range of Nepal changed between 2012 and 2020. We systematically surveyed ~ 42,000 km² of potential habitat, by dividing the study area into 159 grid cells of 15x15 km² and recording elephant signs during the cool dry season in three years (2012, 2018 and 2020). We analyzed the survey data in a single-species multi season (dynamic) occupancy modeling framework to test hypotheses regarding the influence of environmental and management conditions in landscape use by elephants over time. The best-supported model included protected area effects on initial use, colonization, and detection probability as well as temporal variation in colonization and detection probability. Initial use and colonization rates were higher in protected areas, however elephants increasingly used both protected areas and outside protected areas, and the difference in use between protected areas and outside protected areas declined as elephants use became prevalent across most of the landscape. While elephants were patchily distributed in the first year of surveys consistent with past descriptions of four sub-populations, elephant use consolidated into a western and eastern region in subsequent years suggesting two sub-populations. The only gap in their distribution occurs in the area west of Chitwan National Park and east of Banke National Park. Increasing elephant use outside protected areas may cause higher human-elephant conflicts. Management interventions that focus on reducing conflicts can promote human-elephant co-existence in the landscape.