Resource utilisation by smooth-coated otter in the rivers of Himalayan foothills in Uttarakhand, India

Abstract

Conservation depends on acquiring timely knowledge on species’ ecology to alleviate the risks of biodiversity loss driven by anthropogenic stressors. Himalayan freshwater ecosystems are exceedingly threatened by the compounding effects of rising developmental pressure and climate change, jeopardizing biodiversity nested within this imperilled landscape. Riverine ecosystems of the Himalayan foothill forests of India are a stronghold of the vulnerable smooth-coated otter populations. This study entails the understanding of resource utilisation by the smooth-coated otter ( Lutrogale perspicillata ) in terms of habitat use and dietary composition in seven rivers along the Himalayan foothills in India. We surveyed 121.09 km of rivers for otter signs and associated habitat variables. Using Generalised Linear Models, we assessed the factors influencing otter habitat use. We estimated the relative abundance and catch per unit effort of fish species and evaluated otter diet based on spraint samples ( n = 120) using frequency of occurrence and score-bulk estimate methods. Habitat use by otters is governed by a combination of habitat components, which are intricately linked to different requirements such as feeding, grooming, and denning. We found that habitat use was positively associated with channel depth, moderate vegetation, and bank substrate types – bedrock, boulders, sand, and grass. Whereas, increasing distance to escape cover, sparse vegetation, channel width, and anthropogenic disturbance negatively influenced habitat use. Dietary analyses revealed that relatively abundant fish species viz. , Tor putitora and Barilius vagra , predominated the diet of otters. Echoing the principles of optimal foraging theory, our results indicated that small-medium sized fishes of the size range 79.05–199.92 mm, were consumed more often, and larger fishes (> 263.24 mm) were consumed opportunistically. Our findings provide important conservation insights on the status of the smooth-coated otter, their interactions with different habitat components, and dietary spectrum in rivers of the Himalayan foothills. Overall, our study gives cognizance to the importance of preserving freshwater and riparian habitats to ensure the persistence of otters and their prey in the region.