The Influence of Bottom-Up and Top-Down Effects on the Density and Distribution of Common Leopards in the Eastern Himalayas

Leopards (Panthera pardus fusca) are widely distributed across Asia, yet their conservation is overshadowed by the conservation status of other flagship predators like tigers (Panthera tigris), in the Eastern Himalayas. Despite their ability to coexist with other large carnivores, leopard populations are shaped by intricate ecological interactions and increasing human pressures. This thesis investigates the abundance and density, habitat use, and drivers of persistence of leopards across Bhutan to inform multi-species carnivore conservation planning. My first chapter provides an overview of the ecological roles of large carnivores and how they persist on the landscape. I review the mechanisms that facilitate both bottom-up processes, such as prey availability and habitat quality, and top-down forces, such as competition with tigers and human disturbance, on shaping large carnivore populations. I also discuss the significance of studying leopards in Bhutan’s montane landscapes, where a network of protected areas and biological corridors presents a unique opportunity to assess multispecies coexistence. In the second chapter, I use a nationwide camera trap dataset to evaluate how ecological and anthropogenic variables influence leopard density, habitat use, and vital rates. Spatially explicit capture-recapture models were used to produce the first estimate of leopard abundance in Bhutan (318.73 ± 21.73 SE individuals, density 1.02/100 km²), while dynamic two-species occupancy models revealed patterns of habitat use, colonization and local extinction. I found that bottom-up factors, particularly elevation, stream density, and prey availability, played a stronger role than top-down pressures, such as interspecific competition with tigers and human impacts. Contrary to expectations, tiger presence did not negatively impact leopards; instead, colonization was higher where tigers were persistently present, suggesting potential coexistence in preyrich landscapes. I found limited support for the human shield effect, whereby leopards may use human dominated areas more intensely where competitive pressures from tigers are high. Additionally, temporal activity analyses showed high overlap between leopard and tiger diel activity patterns, further supporting the potential for coexistence through fine scale partitioning in resource use rather than temporal avoidance. Finally, in the third chapter, I synthesize my findings in the context of Bhutan’s conservation priorities and propose that leopards be more explicitly integrated into multispecies and connectivity planning. My results support the viability of a guild-based conservation approach, where the recovery of dominant umbrella species like tigers may also benefit subordinate carnivores like leopards. This work advances our understanding of carnivore ecology, especially leopard ecology in the Himalayas and contributes to evidence-based conservation strategies for Bhutan’s diverse carnivore community.