Monitoring tiger and its prey in Chilla range, Rajaji National Park, Uttaranchal, India

Abstract

The Rajaji National Park along with the adjoining Corbett Tiger Reserve forms the north-western limit for the distribution of the Tiger and Elephant in the Indian Subcontinent. Most parts of this landscape are under anthropogenic influence. Following the notification of the earlier sanctuaries (Rajaji, Motichur & Chilla) to a National Park (Rajaji National Park) in 1983, voluntary relocation of human (Gujjar community) settlements is underway (since 2002). The Chilla Range of Rajaji National Park is presently void of human settlements (Gujjars) and is showing very healthy resurgence of vegetation indicating promising signs of recovery with respect to utilization of the area by wildlife. This study carried out across two years (2004- 2005 to 2005-2006) aimed at monitoring the tiger population within Chilla range following a human resettlement program. Photographic capture-recapture analysis (450 trap nights each year) was used to estimate the density of tigers. Ecological density of wild ungulate prey species was estimated using line transects in conjunction with distance sampling. A total of nine permanent transects were laid and sampled eight times each, every year (102.8 km of walk each year). Food habits of tiger were determined by analysing field collected scats. Our results indicated that Chilla range supports a high ungulate prey density (76.5 individuals km-2 in 2005; 70.98 individuals km-2 in 2006) and has the highest reported sambar density (25.67 individuals km-2 in 2005; 24.69 individuals km-2 in 2006). Though we photographed 12 different individuals during our study (2004-06), the tiger density was found to be low (3.01 tigers 100km-2 in 2005; 2.54 tigers 100km-2 in 2006). The current wild prey biomass off take by tigers was estimated to be 2.78%. However, a predicted ~14 tigers 100km-2 can be supported within Chilla range given a 10% biomass off take (following the model developed by Karanth et al., 2004b). Past anthropogenic pressures have probably caused a downward trend in the tiger densities. From the photographs obtained during this study, it is clear that tigers are breeding in Chilla range. Given adequate protection Chilla can serve as a major source population from where tigers will breed and disperse into neighbouring forests within the Shivalik landscape. A continuous monitoring program is envisaged to document this recovery of predators, prey and their habitat