DEMOGRAPHY AND HABITAT USE BY GREATER ONE-HORNED RHINOCEROS IN NEPAL

We used a register of photographed individuals to census greater one-horned rhinoceros (Rhinoceros unicornis, hereafter rhinoceros) in Royal Chitwan National Park (NP), Nepal, between 1984 and 1988. By April 1988, the population was estimated to be 358-376 individuals as determined by regression analysis. The observed rate of increase for the Sauraha population, an intensively monitored subpopulation in the central and eastern part of Royal Chitwan NP, was 4.8% between 1984 and 1988 and 2.5% between 1975 and 1988. The Sauraha population included 87 adult females and 58 breeding-age males, of which only 28 males were judged to have bred during the study period. Annual calf production averaged 7.6 +/- 0.8% (xBAR +/- SE) between 1984 and 1988. No distinct season of parturition was detected. Predation by tigers (Panthera tigris) accounted for 4 of 7 calf mortalities, and all 7 calves that died during the study period were < 8 months old. Mean annual mortality within the calf, subadult, and adult age categories was estimated to be 2.8, 2.2, and 2.9%, respectively. Rhinoceros populations reached maximum densities of 13.3/km2 in riverine forest-Saccharum spontaneum grassland mosaics along the Rapti River. Local densities in areas dominated by Narenga porphyracorma and Themeda arundinacea grasslands were 1.7-3.2/km2. Annual monsoon floods were responsible for maintaining prime grazing habitat and high population densities.