Group Living is a widespread phenomenon within the animal kingdom and has attracted considerable attention in a number of different contexts. This book is focused on the unifying concepts regarding group behaviour that have been developed over the last two decades. The authors set out to discuss the mechanisms that govern the evolution and maintenance of grouping behaviour throughout the animal kingdom, and the ecological factors that control observed group size and group composition in particular situations. Although the book's emphasis is on the elaboration of a conceptual framework, extensive examples and case studies illustrate the diversity of grouping phemonema across taxonomic boundaries, and demonstrate the general applicability of the concepts involved. This book will familiarise the reader with the latest ideas on the ecology and evolution of group-living animals, providing a summary and critical synthesis of the extensive and diverse literature on the subject.