Setting recovery targets for a charismatic species in an iconic protected area complex: The case of tigers (Panthera tigris) in Chitwan-Parsa National Parks, Nepal

The Global Tiger Recovery Program has identified enhancing prey populations as a crucial component in achieving its target of doubling wild tiger (Panthera tigris) numbers, as prey density is a key determinant of tiger density. We estimate prey abundance and ecological carrying capacity (ECC) of tigers in the 1579 km(2) Chitwan-Parsa source site complex within a globally significant tiger conservation landscape in south-central Nepal. Surveying 605.1 km of line transects in the Terai plains and Chure hills of Chitwan-Parsa, we estimated an overall density of 55.43 (36.98-83.45) ungulates/km(2), and a biomass of 244,630 (151,520-334,270) kg/100 km(2) of five abundant ungulates. Chitwan supports 71.58 (49.02-104.71) and Parsa 30.91 (18.70-51.19) ungulates/km(2). The prey base can support 177 (119-263) adult tigers based on energetic requirement models. The tiger ECC was similar to 3.5x higher in Chitwan than in Parsa at a park level. Although opportunities for further recovery of tiger and prey through targeted habitat management exist, the current population of 170 tigers indicates that this population has likely reached its current ECC. We recommend that policymakers and park managers change focus from increasing tiger numbers to developing pre-emptive conflict mitigation strategies to allow the site to retain the successes it has realized.