Estimating Wild Tiger (Panthera tigris Linnaeus) Abundance and Density using a Spatially-explicit Capture-recapture Model in Jigme Dorji National Park, Bhutan

Abstract

Wild tiger populations have rapidly declined in most of the range countries, and there is an urgent need to reliably estimate their numbers for effective management. The use of remotely-triggered camera traps has proven to be an efficient method to sample populations of highly elusive animals such as tigers. In addition, the spatially-explicit capture-recapture (SECR) models are the latest developments in estimation methods to reliably estimate animal density and abundance. Therefore, the objectives of this study were to reliably estimate the density and abundance of tigers and to study their distribution in Bhutan’s Jigme Dorji National Park (JDNP) using the latest sampling and estimation methods. During 7,462 trap-days with 41 camera traps functionally stationed for 6 months in
approximately 656 km2 of highly probable areas of tiger occurrence in JDNP, 80 photographs of tigers (48 right flanks and 32 left flanks) were obtained. Analysis of all left flank pictures yielded seven unique tiger individuals. The SECR model, using an R programme package “SPACECAP” which uses Bayesian framework for inference, estimated the tiger abundance of 19 (SE = ± 6, 95% CI of 9 to 29 individuals) and the density of 3.7 (SE = ± 1.1, 95% CI of 1.8 to 5.8 individuals) per 100 km2. Photographic recaptures and the SECR model yielded the highest tiger density occurring in the south-central region of the park. Using the model estimates, we determined that JDNP can support a maximum of 59 tigers. We posit JDNP as an important tiger conservation area in the upper Himalayan region of Bhutan