Estimating population densities and biomass of ungulates in the temperate ecosystem of Bhutan

Abstract

AbstractIn this study I estimate population densities and biomass of the major prey species of tiger Panthera tigris, leopard Panthera pardus and dhole Cuon alpinus in Bhutan’s temperate ecosystem and recommend measures for reducing crop damage whilst simultaneously protecting ungulate populations. Thirty-two transects totalling 849 km were walked to estimate densities and biomass of ungulates and primates in Bhutan’s Jigme Singye Wangchuck National Park during 2005–2006. Adequate detections (> 40 sightings) for analysis using Distance were obtained for wild pig Sus scrofa (n = 54), muntjac Munticus muntjac (n = 102) and sambar Cervus unicolor (n = 48). Because of similarity in morphology and habitat use, density of serow Capricornis sumatraensis was estimated using the detection probability for sambar. Detections for langur Trachypithecus geei and macaque Macca mulatta were combined (n = 39) to estimate primate density. Mean estimated densities were 3.68 wild pig, 2.17 muntjac, 1.19 sambar, 2.37 primates and 0.36 serow km-2. The three primary prey species of large predators, wild pig, sambar and muntjac, provided a biomass of 379 kg km-2, which could support up to 1.2 tigers per 100 km2. However, the presence of other sympatric carnivores competing for prey in the same area suggests that the actual number of tigers that could be supported is lower. Livestock (density, 6.0 km-2; biomass, 615 kg km-2) apparently supplement prey availability. Ungulate density in the study area is generally low compared to other areas in the Indian sub-continent, and this may be due to conflicts with farmers, excessive grazing of livestock in the forest and the rugged terrain.