The topic of animal motivation deals with how and why animals engage in particular activities: what mechanisms inside the animal generate behaviour, how stimuli from the external environment in­ fluence these mechanisms, and how this behaviour is beneficial to the animal. The topic is thus central both to academic studies in psychology and zoology and to applied matters in domestic species. Motivation has not been an area of great emphasis in the past 10-15 years but there is now a growing realization that it should receive greater attention. Drawing on concepts and observations from a number of areas, this book provides an overview of the motiva­ tional processes which determine the choices, timing, and sequencing which are characteristic of animal behaviour. Data and theory from ethology, psychology, and evolutionary biology are synthesized into a contemporary framework for analysing such central features of behaviour as persistence in activities and goal orientation. Principles of motivational analysis are discussed and illustrated with specific case studies. The successive chapters deal with ethological, phy­ siological, and ecological approaches involving experimental work on a diversity of vertebrate and invertebrate species. Ethological topics include the interaction of external stimuli and internal states, mechanisms of choice, quantitative models of motivation, conflict between tendencies for different activities, and behavioural homeos­ tasis. The review of physiological research focuses on hunger, the activating roles of nerves and hormones, and the examination of animals with small nervous systems.