Gharial abundance in Rapti river, Chitwan, Nepal

Gharial (Gavialis gangeticus) is a Critically Endangered crocodilian species whose abundance in Nepalese rivers are low due to the threat they face. We estimated gharial abundance in the Rapti River, one of the major rivers in Chitwan National Park (CNP) holding the largest numbers of gharials in Nepal. The Rapti River, running across the CNP, was divided into 18 segments, each measuring ~4 kilometers, and gharials were counted directly with three replicates. Gharial count data was analysed using an N-mixture model (negative binomial) and the overall occupancy of gharials was estimated using a single season occupancy model. Covariate effects were also investigated on gharial abundance. Our findings revealed that the Rapti River is home to 150 gharials (119 - 181), with a mean abundance of 8.3 (SD= 3.45) across each segment. The presence of humans and square of Rapti River depth were the significant covariates that had a negative and positive impact on gharial abundance, respectively. Si...