This fifth edition of "Animal Behavior" shows how biologists analyze all aspects of animal behaviour. The book is contains a balanced treatment of both the underlying mechanisms and the evolutionary causes of behaviour. Important concepts are explained by reference to illustrative studies which are described in sufficient detail to help students appreciate both how researchers have carried out their work, and its theoretical significance. Examples are drawn evenly from the vertebrates and invertebrates, and are supported by more than 1000 reference citations many of them publications that have appeared in the last three years. As in previous revisions, Dr. Alcock has completely rewritten the book which includes new examples, citations, and illustrations as well as an expanded set of colour plates which are cross-referenced in the text. Although the book mantains its fundamental organization based on proximate and ultimate topics, there is a new chapter on communication and the chapter on parental care has been moved to better bridge the chapters on reproduction and social behavior. Still more emphasis has been placed on identifying alternative hypotheses, predictions and tests, so that readers can better understand the logic underlying scientists' efforts to discriminate among competing explanations. The discussion questions have also been revised to cover a broader range of conceptual issues.