Species re wilding , as a pivotal strategy for rescuing endangered species and rebuilding wild populations, fundamentally relies on the behavioral plasticity of the re wilding species. Although most current re wilding initiatives select optimal habitats, research on behavioral adaptation mechanisms in more challenging, extreme environments remains lacking. The Milu (Elaphurus davidianus), a typical wetland and plain species, naturally inhabits the warm marshlands of the Yangtze and Yellow River basins. In this study, using GPS tracking data, we focused on a population of re wilding Milu on the Inner Mongolia Plateau to investigate behavioral plasticity in terms of home range area, activity rhythm, and dispersal distance. Our aim was to elucidate their survival adaptation strategies within mid-elevation and cold environments. The results indicate significant seasonal and sex -based differences in both home range and dispersal distance: home ranges contract and dispersal distances are minimized during winter, while spatial activity expands markedly in summer—and continues to increase year by year following re wilding . During the study period, the number of daily activity peaks per individual ranged from zero to four. Furthermore, peak timing exhibited clear seasonal variation, with crepuscular patterns—morning and evening activity peaks—predominant across most months. Approximately three months after release, the activity rhythms of both males and females stabilize. These findings reveal key behavioral adaptations of Milu to alpine and cold climates and furnish a scientific basis for long-term management and ecological adaptability assessments of rewilding populations.