Influence of microhabitat and landscape-scale factors on the richness and occupancy of small mammals in the northern Western Ghats: A multi-species occupancy modeling approach

Abstract

Human-dominated ecosystems are characterized by three main processes, viz., habitat degradation, habitat loss and habitat fragmentation, these posing a great threat to biodiversity. However, the relationships between these processes are not clearly understood. Moreover, habitat loss and habitat fragmentation occur at landscape-scale and their effects depend on the spatial scale. We trapped small mammals in a human-dominated area in the northern Western Ghats, India, at 23 sites in three habitats, capturing 479 individuals of 17 species. We adopted the multi-species occupancy model (MSOM) approach within a Bayesian framework to assess species site occupancy using microhabitat-scale and landscape-scale variables measured at five spatial scales. We found that species richness had a hump-shaped relationship with landscape complexity, and it can be best explained at a spatial scale of 300 m. The findings suggest that both microhabitat-scale and landscape-scale variables influence small mammal occupancy. Overall, shrub density had a positive effect on species occurrence with high certainty, which could be related to the protection provided by shrubs from predators and harsh weather conditions. Shrub density was largely influenced small mammal richness and occupancy and thus should be managed appropriately for their conservation. Considering the negative impact of landscape complexity on endemic rodents, especially on the Critically Endangered Millardia kondana, further fragmentation of grasslands and forest habitats and their conversion into unsuitable habitats in the area should be minimized. All high-elevation grasslands important for M. kondana should be strictly protected and managed. We recommend adoption of the MSOM approach in similar studies, as it allows estimation of occupancy even for species with low detectability.