Beyond sightings: Ensemble modelling to identify conservation hotspots of Smooth-coated otters (Lutrogale perspicillata) in the Ganga River Basin for informed policy and sustainability.

Abstract

Among the three species of otters found in India, viz. the Smooth-coated otter (Lutrogale perspicillata), Eurasian otter (Lutra lutra), and the Asian small-clawed otter (Aonyx cinereus), the Smooth-coated otter has the widest distribution. Historically, the Himalayan foothills and the Gangetic floodplain constituted the stronghold of Smooth-coated otters; however, changing land uses to accommodate growing human populations have led to extensive habitat loss. Despite its ecological importance as a top predator and indicator of river health, systematic, basin-scale assessments of Smooth-coated otter habitat remain limited. In the Ganga River Basin (GRB), available occurrence records are sparse, spatially fragmented, and largely opportunistic, constraining the identification of priority habitats and the formulation of effective, evidence-based conservation strategies. To address this knowledge gap, we undertook comprehensive boat-based visual encounter surveys and complemented by secondary occurrence data to evaluate habitat suitability for otters across the GRB. We surveyed approximately 7,680 km of the river stretches across 22 tributaries, including the mainstem Ganga, between 2016 and 2024. We performed habitat suitability using Ensemble modelling, incorporating 26 predictor variables. The model yields high predicted accuracy, with an AUC value of 0.91 ± 0.03 and a TSS of 0.71 ± 0.06. Distance to Protected Areas (PAs) and distance to rivers emerged as the top predictor variables that highly influenced the habitat suitability for the Smooth-coated otter. Habitat suitability indicated that only 0.26% of the area constitutes highly suitable habitats for the species in the GRB. Overall, our findings provide key insights for conservation planners and managers for developing otter conservation strategies in the Gangetic floodplain of India.