Resource Use and Distribution of Smooth-Coated Otter (Lutrogale perspicillata) in the Sub-Himalayan Foothill Rivers of Uttarakhand

Abstract

Otters are the apex predators of the wetland ecosystems they inhabit. Being sensitive to both pollution and habitat destruction, the presence of otters in a wetland ecosystem, be it rivers, lakes, swamps, mangroves or estuaries, indicates the occurrence of a viable prey base, thus indicating an ecologically healthy condition of such ecosystems. Coupled with habitat, prey is one of the major factors that limit species populations. Many species, including otters, are often seen to cope up with disturbed surroundings only for the easy accessibility or abundance of prey in those areas. The aim of this study was to understand the ecology of Smooth- coated Otter (Lutrogale perspicillata) in terms of their habitat requirements, food habits, and distribution across the landscape. The study was conducted in select rivers of Rajaji National Park and Tiger Reserve, Lansdowne Forest Division, and Corbett National Park and Tiger Reserve. These protected areas fall in sub-Himalayan region, a region of high biodiversity value threatened by immense anthropogenic pressure. Habitat parameters were measured at every 250 m along a river bank and also in locations where there were otter evidences. The importance of different habitat parameters influencing otter occurrence were analysed using Generalised Linear Models (GLMs) and non-mapping technique using Bonferroni confidence interval approach. Smooth-coated Otter significantly preferred deep pools with moderate to sparse bank-side vegetation during the mid-winter and late-winter season. Moderate width water bodies are preferred over narrow water bodies. Muddy and sandy bank substrate types were preferred. Rocky stretches were largely avoided. Water body type i.e. pools and bank substrate type, i.e. rocky substrate, are the significantly influencing factors on otter distribution. Feeding habit of otters were studied by analysing 120 spraints collected throughout the study area. In this study, we also explored how the habitat suitability modelling could predict the percentage of area and a gradient of environmental conditions suitable for the occurrence of Smooth-coated Otter across the study area. MaxEnt modelling was used to predict habitat suitability of Smooth-coated Otter across the landscape. The most important variables affecting otter distribution were compound topographic index, Euclidean distance from the river, and slope position index. With increasing distance from water, and increasing slope, the suitability of an area to sustain otter populations decreased.