Ecological correlates of giant squirrel (Ratufa bicolor) microhabitat use in a lowland tropical forest: implications for matrix management

Giant squirrels are imperilled across their distributional range as a result of anthropogenic disturbances; converting tropical landscapes into mosaics of small habitat patches interspersed within an inhospitable matrix of agricultural land, plantations and human settlement. With limited understanding of Ratufa bicolor ’s habitat relations in the lowland tropical forests, this study aimed to understand the correlates of habitat use from an isolated habitat patch and its adjoining matrix in the Brahmaputra valley which represents the northern distribution limit of the species. The ecological dataset comprised of grid-based spatial occurrence data summarized as average squirrel encounter rate (4 temporal replicate transect surveys in each grid), as well as a range of fine spatial scale ecological covariates (14 habitat attributes). We used generalized linear models and principal component analysis to characterize relationships between squirrel abundance and habitat variables representing different aspects of forest, i.e., structure, composition and food availability, anthropogenic disturbance and edge influence. Our study revealed giant squirrels’ selection of habitat patches to be based on concentrated areas of critical habitat attributes with strong support for the influence of canopy connectivity, canopy density, overall tree density and availability of food tree. Further, a quantitative model for habitat use was evaluated using GLM linking squirrel abundance to the predictive parameters representing different forest aspects, with the best fit model highlighting the positive interaction effects of forest structure and forest composition. The findings from the study provide insights into the necessity of maintaining associated habitat matrix to serve as complimentary space, ensuring future survival of arboreal mammals in human-modified landscapes.