Human society stands on ecosystem services provided by living organisms. The Introduction of non-native species often implemented to promote ecological functions and services even though such species disrupt native ecosystems. Livestock, for example, are among the most beneficial non-native animals; however, create challenges due to dung accumulation. To mitigate these issues, dung beetles have been introduced as dung decomposers. These beetles contribute to numerous ecosystem functions and services, including nutrient cycling, promoting plants growth, secondary seed dispersal, and fly control. Despite these benefits, the impact of introducing non-native dung beetles on native dung beetle communities remains poorly understood. In this study, we assessed the impacts of the introduction on native dung beetle and livestock dung using population dynamics models and numerical analysis. We examined two scenarios(1) the introduction of non-native dung beetles to native communities that consist native dung beetles specialized for native mammal feces (SituationⅠ), (2) and generalist native dung beetles (Situation II). In Situation I, after the introduction, native dung beetle populations declined. We tested four different fecal preferences of non-natives; as a result, when non-natives preferred native feces, it caused a clear decline of the natives. Livestock consistently decreased regardless of preference. In Situation II, native dung beetles also declined. When the native preferred either native or livestock feces and the non-native did not show an exact preference for both feces, the native declined substantially. Notably, livestock dung does not always decline, some dung-preference combinations resulted in increased livestock dung. Overall, our findings indicate that explicitly considering fecal preference is crucial for understanding the population dynamics of both dung beetles and livestock dung. Future research should also address additional ecosystem services, such as seed dispersal and fly control.