An Introduction to Behavioural Ecology

An Introduction to Behavioural Ecology

JR. Krebs & N.B. Davies
Published in: Blackwell Publishing
Release Year: 1993
ISBN: 0-632-03546-3
Pages: 437
Edition: 3rd Edition
File Size: 38 MB
File Type: pdf
Language: English

Description of An Introduction to

Behavioural Ecology

This brief introduction describes the organization and contents of our book. The book is about the survival value of behavior. We call this subject 'behavioural ecology' because the way in which behaviour contributes to survival and reproduction depends on ecology. If, for example, we want to answer the question 'How does living in a group contribute to an individual's survival?', we have to start thinking in terms of the animal's ecology; the kind of food it eats, its enemies, its nesting requirements and so on. These ecological pressures will determine whether grouping is favoured or penalized by selection. Behavioural ecology is not only concerned with the animal's struggle to survive by exploiting resources and avoiding predators, but also with how behaviour contributes to reproductive success. Much of the book is therefore about competition between individuals for the chance to reproduce and pass on their genes to future generations.
The book emphasizes the theoretical background of each subject discussed, but we prefer to illustrate the theory with examples after a very brief general introduction, rather than developing long, abstract, theoretical arguments. Although none of the ideas we have used is difficult to understand we have placed some of the more complicated arguments and details in boxes which can be ignored if the reader is in a hurry.
Chapter 1 is a general introduction to the book, in which we distinguish between different kinds of questions that one can ask about behaviour. In particular, we emphasize the difference between questions about survival value or function and those concerned with causal mechanisms. We show that natural selection should favour individuals who are best able to propagate their genes to future generations. In Chapter 2 we discuss how to test hypotheses for the adaptive advantage of behaviour. One method is a comparison among species.  The rationale here is that differences between species in behaviour can be correlated with differences in their ecology. From these correlations, inferences can be drawn about the adaptive significance of behavioural traits. We illustrate this approach with reference to social organization in weaver birds, antelope and primates. The second method is to perform experiments, for example, to change behaviour and measure the consequences this has for the individual's chances of survival and for its reproductive success.
In Chapter 3 we focus on the individual. Animals are viewed as making 'decisions' between alternative courses of action and the decisions can be analyzed in terms of their costs and benefits. A powerful tool in this approach is the optimality theory, which allows us to test hypotheses about the importance of various costs and benefits by predicting their effects on the animal's decision rules. By considering the basic decisions underlying behaviour patterns, we show how the same models can be used to understand what at first sight seem very different problems, such as feeding and searching for mates. 
Chapter 4 looks at decisions over evolutionary time, and how these change during arms races between predators and prey, and brood parasites and hosts. In the next three chapters, we consider how individuals should behave when they have to compete with others for scarce resources such as food, territories or mates. We discuss how competitors should be distributed in relation to resource distribution and abundance  (Chapter 5) and the costs and benefits of living in groups (Chapter 6). In Chapter 7 we introduce the idea of game theory as a technique for analyzing how individuals behave in contests for resources.
Chapters 8, 9 and 10 are concerned with sexual reproduction. A consideration of the basic differences between males and females leads to the idea that members of one sex (usually male) may compete for access to members of the other (Chapter 8). This is the theory of sexual selection. The differences between male and female also suggest that the interests of the two sexes during reproduction often differ (the theory of sexual conflict). Chapter 9 discusses how these battles within and between the sexes are influenced by ecology. Here we rely heavily on the comparative approach, correlating differences between species in sexual strategies with differences in ecology. From differences between species, we turn to differences between individuals (Chapter 10). We introduce the idea that different individuals within a species sometimes adopt different sexual strategies. These differences may be related to age or size, or they may simply be equally profitable, alternative, ways of achieving the same end. In Chapter 11 we examine how altruistic behavior can evolve.
We then illustrate the theoretical arguments with reference to 'helpers'; individuals that help others to rear young instead of producing their own. Chapter 12 deals with birds, mammals and fish, and Chapter 13 is devoted entirely to the social insects, where helping reaches its most sophisticated level of development. Many of the earlier chapters refer to communication as a behavioural mechanism of competition for resources and social interaction. In Chapter 14 we tie together these threads in a general discussion of animal signals. We follow the pattern set in earlier chapters by considering both ecological constraints and intraspecific selection pressures. In the final chapter we reassess the view that the survival value of behaviour can be understood within a neo-Darwinian framework using methods such as optimality models and game theory.
Finally a word about the style of presentation. We generally use convenient and informal shorthand rather than traditional formal scientific style. A phrase such as 'Offspring are selected to demand more food than the parent wants to give' is short for 'During the course of evolution selection acting on genetic differences in the begging behaviour of offspring will have favoured an increase in the intensity of begging. This increase will have been favoured to the extent where the level of begging by any individual
offspring exceeds the optimum level for the parent'. Some readers may wonder whether our informal shorthand, together with catchy descriptive labels for various behaviour patterns such as 'manipulation' and 'sneaker', is a sign of sloppy thinking. There is no doubt that loose terminology can indicate imprecise thinking and half-formulated ideas. But it is equally easy to conceal woolly arguments behind an obfuscating screen of scientific jargon. We have used a simple direct style in order to make our arguments clear and not because behavioural ecology is woolly subject. This point is nowhere better illustrated than by George Orwell in his brilliant essay 'Politics and the English Language' (1946). He translates the following well-known verse from Ecclesiastes into modern English: 'I returned and saw under the sun, that the race is not always to the swift, nor the battle to the strong, neither yet bread to the wise, nor yet riches to men of understanding, nor yet favour to men of skill; but time and chance happeneth to them all.' And now the translation. 'Objective consideration of contemporary phenomena compels the conclusion that success or failure in competitive activities exhibits no tendency to be commensurate with innate capacity, but that a considerable element of the unpredictable must invariably be taken into account. 'This translation is not only tired and ugly, lacking the fresh, vivid imagery of the biblical passage, but it replaces precise illustrations with woolly generalization. While we cannot hope to emulate the clarity and brilliance of the writer of Ecclesiastes, or indeed of George Orwell, we hope we have avoided the worst excesses of the Orwellian parody and presented our ideas in simple but precise language.
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