The Distribution of Elephants, Tigers and Tiger Prey in Thailand’s Western Forest Complex

Abstract

Conservation of large mammals such as Asian elephants (Elephas maximus), tigers (Panthera tigris) and their main prey, gaur (Bos gaurus), banteng (Bos javanicus), and sambar (Cervus unicolor) requires a systematic and statistically rigorous monitoring system that accounts for imperfect detection. Despite conservation efforts, these large mammals are highly threatened and declining across their entire range. In Thailand, large viable populations of these large mammals remain in the Western Forest Complex (WEFCOM), an approximately 19,000 km2 landscape of 17 contiguous protected areas. To determine species distribution and factors that affect distribution patterns, a government/NGO team conducted occupancy surveys throughout the WEFCOM landscape from 2010-1012. I analyzed these data at both a landscape scale (256 km2 for elephants, 64 km2 for tigers and their prey) and a local scale (1 km2). At the landscape scale, I estimated the proportion of sites occupied by each species. At a finer scale, I identified the key variables that influence site-use and developed predictive distribution maps. At both scales, I examined key ecological and anthropogenic factors that help explain distribution and preferred habitat use. Occupancy models revealed that elephant, gaur and sambar avoided villages and elephants, banteng and sambar prefered lower slopes near streams. Gaur, in contrast, preferred steep slopes at higher elevation. I estimated that elephants occupied 82% of the the landscape. Other species occupied much smaller portions of WEFCOM (tigers = 37%, gaur = 48%, sambar 53% and banteng 13%). Tiger occupancy was largely influenced by the three large prey species. Additionally, presence of villages has a consistent negative impact on occupancy and site-use by all these large mammals; therefore, reducing the impact of human activities near villages is the key conservation recommendation from this study. By modeling occupancy while accounting for probability of detection, I established reliable benchmark data on distribution of these endangered species. The results of this study underlined the need for further conservation and management to maintain wildlife distribution and populations in WEFCOM and other sites in Thailand and Southeast Asia.