It has often been assumed by those studying animal behaviour that the social system adopted by a species is a fixed product of natural selection. There is now an interesting body of evidence that this is not always the case and that alternative forms of social organisation may be adopted according to circumstance. In this book, first published in 1991, Professor Lott presents an overview of the understanding of this phenomenon and its implications for animal conservation and management. Those interested in social systems and more generally in animal behaviour and ecology will find this book to be an invaluable source of information and ideas.