Simple SummaryThis study aims to investigate the behavior and ecology of nutria (Myocastor coypus), a semi-aquatic rodent that was introduced to South Korea for commercial farming and subsequently damaged aquatic ecosystems after its release. How the behavioral ecology of introduced nutria changes over time and across seasons remains unclear. Twenty-four adult nutria (twelve males and twelve females) were radio tracked in 2015–2016 to identify their home range size and activity patterns in the Macdo wetland, South Korea. This study found that the nutria home range size varied seasonally, with males having larger home ranges than females. Additionally, nutria showed crepuscular and nocturnal activity patterns throughout the year, with no significant difference between sexes. The findings of this study provide crucial information on the home range and activity patterns of introduced nutria in the Macdo wetland, which can guide management efforts to mitigate their impacts on the ecosystem. It is the first quantitative analysis of the home range and activity patterns of introduced nutria based on radio tracking data in the Macdo wetland.AbstractNutria (Myocastor coypus) are semi-aquatic rodents that were introduced in South Korea for commercial farming but significantly damaged aquatic ecosystems. Understanding nutria ecological behavior is essential for developing effective control and eradication strategies to mitigate their impacts. Thus, this study aimed to investigate the home range and activity patterns of 24 nutria (12 males and 12 females) in the Macdo wetland in South Korea from 2015–2016 through radio tracking. The average minimum convex polygon home range of the nutria was 0.29 ± 0.55 km2, with a 95% kernel density estimation (KDE) home range of 0.43 ± 0.85 km2and a 50% KDE home range of 0.05 ± 1.1 km2. The home range of males was larger than that of females; however, the winter home range of females was as large as that of males. The home range also varied seasonally, with the smallest observed in winter. The nutria showed crepuscular and nocturnal activity patterns throughout the year, with no significant difference between sexes. The activities in spring, summer, and autumn showed no significant differences, but the activity in winter was significantly different from that in the other seasons. This study may serve as a basis for developing appropriately timed and scaled management strategies to mitigate the impacts of nutria on ecosystems. In conclusion, several environmental and biological factors contribute to the behavior of nutria in South Korea.