Estimation of tiger densities in India using photographic captures and recaptures

Karanth and Nichols extended camera-trap capture-recapture into a full density-estimation framework applied across multiple Indian reserves. They combined closed-population abundance estimates from photographic recaptures with a sampling-area correction based on the mean maximum distance moved by photographed tigers, buffering the trapping polygon to derive density (tigers per 100 square kilometers). The study formalized field protocols such as dual cameras per station to capture both flanks, adequate station spacing relative to home-range size, and survey durations short enough to satisfy demographic closure. Density estimates ranged widely across sites, reflecting prey abundance. This paper is the canonical Karanth-Nichols framework that standardized tiger monitoring and is the single most cited methodological reference for photographic density estimation of individually marked carnivores.