Landscape analysis of tiger distribution and habitat quality in Nepal

Despite more than two decades of conservation efforts, only limited information is available on the metapopulation structure of the tiger (Panthera tigris). We report on the geographic distribution of tigers in Nepal in relation to habitat quality and describe an inventory and monitoring system that can be applied across the entire range of the species. Using information from previous studies, interviews with local people, and digital thematic mapper satellite data, we identified four populations of tigers; three occur primarily within the borders of Nepal, and a fourth is across the border in India. We estimate that there are 153 breeding tigers in these four populations. In the Chitwan population, 77% of breeding tigers live in three protected areas; the rest occupy national forests. Tigers in all four populations survive in isolated forest remnants of what was once a continuous subtropical forest zone lying south of the Himalayas. Within central Nepal the ratio of good- to poor-quality tiger habitat ranged from 16% to 86% across seven forest districts. The four areas with the highest ratio of good-quality habitat (>54%) supported breeding populations, one area with a marginal ratio of good-quality habitat (46%) was used only occasionally, and the two areas with the lowest ratio of good-quality habitat (<26%) were not used by tigers. We suggest that when the ratio of good to poor habitat drops below approximately 50% tigers no longer breed; when it drops below 30% tigers no longer occur in an area. Estimates of potential tiger habitat and data on habitat used by tigers demonstrate the need to expand current management beyond parks to encompass the entire land base supporting these fragmented populations so that small tiger populations can be managed as ecosystem or tiger management units rather than as portions of populations within protected areas.