Quantification of eradication thresholds for free-ranging dog populations using population viability analysis

Free-ranging dogs pose considerable challenges to public health, biodiversity conservation, and animal welfare. Although release-based management programs have been implemented successfully in some countries, they are not permitted in Japan. Sustained removal is therefore required, but the capture intensity needed to achieve local eradication remains unclear. We quantified the capture intensity required to eradicate a free-ranging dog population using population viability analysis. A two-stage Leslie matrix model was parameterized with population estimates from camera-trap surveys, placental scar counts, and published survival rates. Population dynamics were simulated over 10 years using 5,000 Monte Carlo iterations. Demographic contributions to population growth were assessed using elasticity analysis. The estimated annual finite rate of increase was λ = 1.535, indicating that the population could double within approximately 19 months without intervention. Simulations showed that annual capture of approximately 35 adult dogs shifted the population trajectory from growth to decline, whereas annual capture of 50 adult dogs resulted in eradication within 10 years in approximately 96% of simulations. Adult survival contributed substantially more to population growth than reproduction (85.5% vs. 3.9%). Sustained removal of adult dogs, combined with reductions in anthropogenic food resources, is likely to be an effective strategy for eradication under demographic conditions similar to those observed in the present study.