Noninvasive genetic monitoring of tiger (Panthera tigris tigris) population of Orang National Park in the Brahmaputra floodplain, Assam, India

The Brahmaputra Valley of Assam, India, is one of the prime habitats for the endangered Royal Bengal tiger Pantheratigris tigris. With dwindling global population, estimation of the minimum number of tigershas always been a curiosity to wildlife researchers as well as to protected area managers. In the present study, DNA-based techniques were used for identifying individual tigerspresent in Orang National Parkof Assam, from 57 faecal samples collected during February 2009. Orang National Parkstands as an island of a single forest patch along the north bank of river Brahmaputra. The present study confirms the presence of 17 individual tigersin Orang National Park, with five male and 12 female. DNA-based capture–recapture analysis yielded minimum range estimate of 18 and 19 individuals, with possible overestimates of population size following two models of capture probability in CAPWIRE. The results of our genetic counting of tigersare compared with the estimates of 19 tigersbased on pugmarkanalysis by the state ForestDepartment in 2000 and an independent capture–recapture estimate of 14 (±3.6) individuals based on photographic identity study in 2009. Looking at high mortality of tigersin the area, with 19 reported deaths during 2000 to 2009, our results indicate high individual turnover in the area. This study shows that Orang National Parkharbours a healthy breeding population of tigers. However, the possibility of a source-sink dynamicsoperating in the landscape could not be ruled out, with possible immigration from nearby Kaziranga National Parkon the south bank of Brahmaputra, which has the highest reported density of the species in the world.