In this paper, we discuss the immersive sonification of an artificial ecosystem in the form of an interactive augmented reality music composition, named Proprius. We first offer an overview of existing work that utilizes ecological models in artistic contexts. We then describe the ecosystemic models employed in Proprius. We evaluate the musical characteristics of animal behaviors, and discuss our approach to sonifying and spatializing them in the context of an interactive augmented reality composition. We provide details of our system in terms of how it implements ecological simulation, real-time sonification, immersive audio, and human-computer interaction.