Ecological factors that influence sambar (Rusa unicolor) distribution and abundance in western Thailand: Implications for tiger conservation

Prey density is declining throughout the tiger's (Panthera tigris) range and knowledge of the ecological factors that affect prey distribution and abundance remains surprisingly limited for this globally endangered species. In this study, we examined the ecological variables infl uencing the abundance of sambar (Rusa unicolor), the dominant prey species for the tiger across its global southern range. We also identifi ed the scale at which these variables impact sambar distribution in Huai Kha Khaeng Wildlife Sanctuary, a high tiger density site in Southeast Asia. The fecal pellet group accumulation method was used to estimate an index of sambar abundance. Pellet groups were counted along 360 line transects randomly placed among four approximately 100 km² sites that encompassed six female tiger home ranges. The relationship between sambar pellet-group counts and 10 environmental variables was investigated using generalised linear mixed models. The sambar abundance index was negatively associated with distance to the largest river in the study area, elevation, and the amount of dry deciduous dipterocarp forest cover. Distribution and abundance of sambar were positively associated with relatively fl at areas of river valleys, presumably due to the quality of vegetation available for foraging and greater visibility for detecting predators compared to other portions of the study area. This study is the fi rst to identify the importance of wide alluvial valleys to tiger prey and suggests this habitat is critical for securing one of the largest tiger source populations in Southeast Asia.