In the early years of this century a Scottish doctor speculated on the evolutionary origin of human tears. It seemed to him that with the increase in brain size and cognitive powers of our early ancestors many events in the struggle for existence would be just too distressing to observe. How comforting then, for the mother, distraught by the sight of her child being devoured by a lion, to cloud her vision with a flood of tears! Just so, though if the good doctor had pondered further, the following picture might have occurred to him, comfortable in his speculative armchair, and given him some pause for thought. ' ~ . . . . ~ . . ~ ~ . . *. . u" . . , ~- . ' _ . . . . . . . vii viii SERIES EDITOR'S FOREWORD These stories do not, of course, get us very far in understanding the evolution of tears or anything else, but they do remind us how far the study of behavioural adaptation has come this century. This is, in fact, an exciting time for students of behaviour. The last twenty years have seen a great advance in the theoretical armoury for tackling questions of behavioural evolution and adaptation, and a parallel expansion in empirical studies, particularly in the field. The concepts of inclusive fitness and the evolutionarily stable strategy, for example, have helped to explain major features of social behaviour and have generated entirely new questions and predictions for the field worker to examine.

Many associations between organisms, both intra-and interspecific, can be usefully regarded as 'producer/scrounger' (P/S) relationships. One or more individuals or species (scroungers) within the association in some way use the behavioural or physiological investment of others (pro ducers) to reduce their costs of obtaining a limited resource. Examples are legion: many parasites take up more or less permanent residence in or on a host individual and use the host's ingestive, digestive or circu latory processes to reduce their own feeding costs; pirate (ldepto parasitic) individuals or species exploit the foraging investment of 'host' individuals/species by stealing procured food; inter- and intraspecific brood parasites exploit the nest-building behaviour and parental care of other species/individuals; non-displaying 'satellite' males may usurp matings (ldeptogamy) from higher ranking males whose display effort has attracted females to a courtship gathering, and so on. Scroungers appear to reduce the costs of exploiting a resource by letting producers invest the necessary time and energy in foraging, building, incubating, displaying, defending, evolving anti-predator adaptations, etc. , and then usurping the results of their efforts. The utility of scrounging, however, is conditional on a number of factors including the availability of producers, the number of scroungers exploiting them, the cost of scrounging in terms of producer avoidance, defence and/or retaliation, the value of the limited resource and the scope for alternative strategies of resource exploitation. This book brings together theoretical and empirical studies of PIS relationships in a wide variety of contexts and species.

The study of animal behaviour, particularly from evolutionary and ecological viewpoints, has been one of the major growing points in biology over the last 10 to 15 years. The degree of quantitative rigour in theoretical, observational and experimental approaches to behaviour has increased dramatically. As more of the rapidly growing research literature be comes a basic requirement for students reading animal behaviour at undergraduate level, there is a need for a readily comprehensible text, covering all major aspects of behaviour study, to accom pany their courses. This book, based on my first, second and third year under graduate lectures at the University of No ttingham, is designed to meet that requirement. The book begins with a discussion of the physiological and anatomical bases of behaviour: the relationship between nervous system structure and function and behaviour; hormonal effects on behaviour; biological c1ocks; perceptual mechanisms; and stimulus filtering. This leads to a consideration in Chapter 2 of how the animal integrates internal and external stimuli in making decisions about its behaviour and the way natural selection has shaped decision-making processes and the organisation of motivation. The first two chapters therefore deal with the instigation or causation of behaviour within the animal. Chapters 3 and 4 deal with developmental aspects of behaviour. Chapter 3 discusses behaviour genetics, inc1uding the relationship between specific genes and behaviour, the heritability of behaviour patterns, the site of gene action in the body and the evolutionary consequences of a genetic basis to behaviour."