Abstract
Free-roaming dogs (Canis familiaris) are invasive species that pose serious threats to wildlife, and this necessitates active management. In Taiwan, resistance to euthanizing shelter dogs has led to overcrowded shelters, which prompted a shift to trap-neuter-return (TNR) as the primary method for managing free-roaming dogs. Shoushan National Nature Park in Kaohsiung, Taiwan has experienced this problem and, therefore, implemented a high-intensity TNR program in 2018–2020. We evaluated effectiveness of TNR in dog population management and its applicability to wildlife conservation in this urban protected area. We conducted camera trapping surveys during 2014–2022 to estimate the population dynamics of dogs and wildlife. The camera traps collected 21,884 trap nights of data and 30,396 trap events of invasive and native mammals. The dog population increased significantly from 2014 to 2017 (relative abundance index (RAI): +318%; occupancy: +17%), which was probably attributed to the implementation of a no-kill policy. Afterwards, the population declined marginally from 2018 to 2021 following the TNR that was conducted (RAI: −29%; occupancy: −9%). In contrast, Reeves' muntjacs (Muntiacus reevesi) decreased significantly from its peak in 2014 to a low in 2022 (RAI: −96%; occupancy: −41%). Similarly, masked palm civets (Paguma larvata) also experienced a decline (RAI: −60%; occupancy: −25%). Population viability analysis predicted that maintaining a sterilization rate of > 75% for female dogs could theoretically control the dog population, but the 50–100 immigrants that entered the population each year would disrupt the effectiveness of the TNR treatment severely. We concluded that TNR was not sufficient in areas with conservation concerns. In addition to neutering, strategies to reduce immigration and to increase the number of dogs removed were crucial for effective management.