Ethology, the study of the biology of behavior, has grown tremendously during the last few decades. The large number of accumulated facts is difficult to survey, understanding and an appreciation of the ethological approach to the study of behavior have grown, and the number of attempts at holistic explanations for certain behavioral phenomena has increased. Because of this development it has become more difficult to gain an overview of the field, to keep up with new developments, and to update the subject matter by the inclusion of new facts in the proper place. The nonspecialist is unable to evaluate the more general statements in the popular literature, especially when such works are aimed at a broader audience. Hence, this book has a dual purpose: (1) to lend some order to the dizzying array of information and thus simplify inquiry into ethology; and (2) to present relevant facts and knowledge that will help the reader confronted with numerous studies and articles in the ethological literature.