Density and carrying capacity in the forgotten tigerland: Tigers in the understudied Nepalese Churia

While there are numerous wildlife ecology studies in lowland areas of Nepal, there are no in-depth studies of the hilly Churia habitat even though it comprises 7642 km(2) of potential wildlife habitat across the Terai Arc. We investigated tiger, leopard and prey densities across this understudied habitat. Our camera trapping survey covered 536 km(2) of Churia and surrounding areas within Chitwan National Park (CNP). We used 161 trapping locations and accumulated 2097 trap-nights in a 60-day survey period during the winter season of 2010-2011. In addition, we walked 136 km over 81 different line transects using distance sampling to estimate prey density. We photographed 31 individual tigers, 28 individual leopards and 25 other mammalian species. Spatial capture-recapture methods resulted in lower density estimates for tigers, ranging from 2.3 to 2.9 tigers per 100 km(2), than for leopards, which ranged from 3.3 to 5.1 leopards per 100 km(2). In addition, leopard densities were higher in the core of the Churia compared to surrounding areas. We estimated 62.7 prey animals per 100 km(2) with forest ungulate prey (sambar, chital, barking deer and wild pig), accounting for 47% of the total. Based on prey availability, Churia habitat within CNP could potentially support 5.86 tigers per 100 km(2) but our density estimates were lower, perhaps indicating that the tiger population is below carrying capacity. Our results demonstrate that Churia habitat should not be ignored in conservation initiatives, but rather management efforts should focus on reducing human disturbance to support higher predator numbers.