Ecology and conservation of the Indochinese tiger (Panthera tigris corbetti) in the Dong Phayayen-Khao Yai Forest Complex in eastern Thailand

Catastrophic population declines threaten the under-studied and Endangered Indochinese tiger (Panthera tigris corbetti) with extinction. Thailand now plays a critical role in the conservation of the Indochinese subspecies, given few known breeding populations in other range countries. Thailand’s Dong Phayayen-Khao Yai forest complex (DPKY) is recognised as a tiger landscape of national importance, though it has been largely understudied. A lack of information on the status, ecology, and conservation of tigers in this landscape undermines effective management and renders an incomplete picture of its role in the conservation of tigers in the region.
The goal of this thesis is to assess the ecology and conservation status of tigers in the Dong Phayayen-Khao Yai Forest Complex. Specifically, through this thesis, I aim to: 1) Assess tiger presence, persistence, breeding, and population density; 2) Explore important associations with habitat, prey, and threats that influence the population; 3) Investigate long-term habitat connectivity and population viability; and (4) Conduct novel assessments on methods commonly used in ecological research.
In Chapter 1, I contextualize the research conducted in this thesis by providing an overview of the conservation history and status of tigers in Southeast Asia and Thailand. This chapter also highlights prevailing methodological trends involved in such research.
Chapter 2 of this thesis represents the first dedicated, long-term study on tigers across DPKY. Here, I describe heterogeneity in the distribution of tigers across the landscape, identify potential prey species, and document long-term persistence of individuals. Importantly, results confirm breeding at the site, establishing DPKY as one of the few remaining breeding populations of Indochinese tigers globally and a tiger landscape of global conservation significance.
In Chapter 3, I investigate the degree to which scale- and functional form (shape)-optimization affect performance of habitat selection models for tigers and conduct a first-of-its-kind assessment of optimization approaches in modelling species-habitat relationships. Importantly, results confirm the importance of optimizing such models for spatial scale while optimizing for functional form did not improve model performance. These results reinforce the importance of broad-scale protection of core tiger habitat in DPKY as part of a landscape-scale management strategy.
In Chapter 4, I evaluate the degree to which prey, human presence, and environmental factors explain tiger presence in DPKY both independently and collectively. I found that tiger presence had strong, positive associations with wild boar (Sus scrofa) presence and prey richness, and strong negative associations with human settlements, public roads, and poacher presence. However, environmental characteristics, particularly confounded with human factors, best explained variance in tiger presence, suggesting these factors could aid in modelling potential tiger occurrence where other data may be lacking.
Chapter 5 of this thesis represents the first dedicated peer-reviewed study to estimate tiger population density in DPKY. Importantly, I utilize simulations to aid in the development, validation, and implementation of an effective survey design, an approach which may be beneficial for similar studies of low-density carnivore populations. While estimated density (0.63 ± SE0.22 [0.32–1.21] tigers per 100km2) and population (20 [14–33]) were relatively low, these key metrics provide a crucial, reliable baseline for evaluating population changes over time.
In Chapter 6, I simultaneously evaluate the potential for DPKY’s tiger population to disperse to other potential habitat and assess the sensitivity of connectivity models to changes in key parameters. Here, I demonstrate that landscape connectivity models can be highly sensitive to parameter values with significant interactions and relative strength of effects varying by timestep. Dispersal ability, mortality risk, and their interaction dominated predictions, underscoring the importance of incorporating these factors in a spatially- and temporally-dynamic framework. Results from this study suggest reasonable dispersal potential of tigers to Khao Yai National Park in DPKY though dispersal and persistence within and beyond the landscape could be drastically undermined by increased mortality.
In Chapter 7, I utilize an individual-based, spatially-explicit population modelling approach to evaluate the effects of landscape change scenarios and mortality risk on the probability of tiger persistence in DPKY as well as model sensitivity to mortality risk, resistance surface transformation, and population density. Mortality risk dominated predictions of population persistence with results indicating strong negative effects resulting from road expansion and construction of dams. The high sensitivity of models to mortality risk and high variability in population trajectories suggest this population is extremely vulnerable to extinction.
Lastly, in Chapter 8, I summarize and synthesize findings from previous chapters. Here, I discuss the implications of this research for the management and conservation of tigers in this landscape, offer perspectives on methods of research in this field, and contextualize results within the broader realms of conservation in Thailand and Southeast Asia.

Keywords: camera trap
landscape ecology
Panthera tigris
Thailand
Indochinese tiger
conservation
Tiger
Dong Phayayen-Khao Yai Forest Complex
Advisor: Macdonald, D
Kaszta, Z