Much of ecology is concerned with the search for repeated patterns. When expressed in a structured, meaningful representation of natural systems, these patterns form the foundation of modeling in wildlife management. Models are built to define problems, clarify ideas, organize concepts, communicate information, develop and test hypotheses, and to make predictions. Thus, models are crucial to the resource decision-making process. 180, 183 Models should be viewed not as scientific laws that represent absolute truth, but rather, as hypotheses that offer a “purposeful representation.” 182 The models we discuss here are used to characterize how animals respond to their abiotic (eg, landform, soils) and biotic (vegetation, species interactions) environment. Animal response can take the form of occurrence, distribution, abundance, movements, productivity, or survival. The intent of this chapter is to: