A low-density yet stable population of Indochinese tigers (Panthera tigris corbetti) may be the key to recovery in a half-empty landscape in eastern Thailand

Abstract

Indochinese tigers (Panthera tigris corbetti), formerly distributed across mainland Southeast Asia, have experienced significant range contraction, with populations in Thailand serving as the last remaining strongholds. One such landscape is the Dong Phayayen-Khao Yai (DPKY) forest complex in eastern Thailand. Despite the landscape's strategic importance for regional tiger recovery, there is a need for policy-aligned evidence to support recovery planning. In this study, we assessed space-use patterns of prey and tigers and factors influencing them, utilising occupancy modelling based on landscape-wide photo-capture data from 2021. Additionally, we evaluated the population dynamics of tigers between 2018 and 2021 by estimating annual population density and vital parameters. Despite the availability of suitable habitat across the 6155 km² landscape, tigers were restricted to the eastern section, utilising only 55 % of the complex, primarily constrained by sambar space-use and landscape connectivity. Nevertheless, the population maintained stability (λ ≈ 1) with high survival (φ > 0.9) and documented reproduction, albeit at low densities (∼1 tiger/100 km²). Anthropogenic factors significantly influenced prey, with larger species such as sambar and gaur exhibiting limited occurrence (ψ <0.4). While the current population appears well protected, evidenced by high survival and reproduction, recovery is constrained by low prey availability and landscape fragmentation, particularly across Highway 304. While considerable recovery potential exists, given the available habitat in the landscape, such recovery necessitates sustained long-term interventions focusing on prey, enhanced protection, and restoration of connectivity. The DPKY represents a critical opportunity for tiger recovery in Southeast Asia, where most landscapes lack tigers.