Research

Life Sciences & Biotechnology

Title :	Patterns and mechanisms driving persistence of medium and large mammals in human-dominated landscapes
Area of research :	Life Sciences & Biotechnology
Principal Investigator :	Dr. Devcharan Jathanna, Wildlife Conservation Society India, New Delhi
Timeline Start Year :	2024
Timeline End Year :	2026

Details

Executive Summary :

Species distributions result from differential outcomes of individual fates, driven by variable habitat selection decisions by individuals in response to biotic/abiotic factors. Individuals often have to settle for less preferred habitats (e.g. because the most preferred ones are occupied), and variation in habitat suitability may exist within habitat types, across ecotones, or across hard edges. My previous research (Jathanna 2016) showed that species used habitats well outside what is normally considered 'preferred' habitat, provided that these latter habitats were contiguous with preferred habitats. I plan to focus on use of coffee plantations by medium to large mammals. By modelling probability of habitat use (derived from occupancy modelling using camera trap data) as a function of distance to the forest-plantation edge, I hope to distinguish species use of human-dominated areas resulting from different mechanisms- 1) Temporary forays by individual animals from forest into plantation areas would be characterised by declines in Pr(habitat use) at relatively small spatial scales. However, forays can be qualitatively different from regular ranging, and may occur over spatial distances larger than the dimensions of home ranges. Therefore declines in predicted habitat use over distances (from the forest-plantation interface) up to twice the home range diameter of a species will be interpreted as forays. Observed declines in predicted occupancy at distances ranging from two to four times the home range diameter will be treated as inconclusive, and declines in predicted occupancy at distances greater than four times the home range diameter will be assigned to the next category. 2) Source-sink dynamics (where populations in low-quality [sink] habitat would decline to extinction in the absence of immigration from high-quality [source] habitat) can sustain species presence far beyond the scale of individual animal movements. Declines in predicted Pr(habitat use) at distances (from the forest-plantation interface) greater than four times the species home range diameter will be interpreted as evidence of source-sink dynamics, with no upper limit as declines in habitat use at any distance provide support to the hypothesis that populations in the sink areas are being maintained through immigration and rescue. 3) Finally, incorrect designation of a species as a forest obligate may lead to plantation areas serving as source sites, where populations persist by reproducing and replacing themselves without need for immigration from a source population to ensure persistence, and this would manifest as no observed decline in probability of habitat use even at very large distances from the forest-plantation edge. Findings would significantly enhance understanding of mechanisms driving species use of coffee agro-forests (not addressed to date), and also provide species-specific strategies to facilitate conservation of these species in human-modified systems.