Home ranges relate to all aspects of a mammal's biology. The 5 papers in this Special Feature provide statistical, economic, game theoretic, mechanistic, information dependent, and conceptual approaches to understanding home ranges and why animals have them. All the papers emphasize the importance of testing a priori hypotheses, especially hypotheses that elucidate why animals behave as they do. All the papers relate resources and habitat quality to home ranges. Finally, the authors oppose viewing home ranges as the product of measurements and suggest viewing home ranges as the cognitive maps that animals maintain and update.