RESUMO
Many animals show multiple patterns of parental care, where more than one of the four basic patterns (biparental care, uniparental care by males or females, or no care) is present within a single population during a single breeding season. We consider three reasons for the existence of multiple patterns of parental care: (1) mixed-strategy behaviours; (2) time-dependent behaviour with parents changing their care decision during the breeding season; and (3) quality differences between individuals leading to different care decisions being made depending on the qualities of both parents. The basic framework we use to investigate these is a two-stage game-theoretical model, and we highlight the importance of including feedback between the parental care decisions made by population members and the probability that a deserting individual will find a new mate. Including this feedback may introduce a nonlinear dependence of the fitness payoffs on the frequencies with which the pure strategies ('care' and 'desert') are played by each of the sexes. This can have important consequences for the existence of evolutionarily stable strategies (ESSs). For example, mixed-strategy ESSs may exist (an outcome forbidden if the feedback is not included) and, in one model, the feedback also prevents uniparental care by either sex from being evolutionarily stable. We also point out that decisions made by animals without dependent offspring can have important consequences for observed parental care behaviour. Copyright 1999 The Association for the Study of Animal Behaviour.
RESUMO
We examine two methods of allocating animals between sites of different resource input rate in the context of the ideal free distribution. The basic models are of individuals of two classes of competitive weight distributing themselves between two sites. The importance of arrival sequence and the subsequent movements of animals between sites are investigated. When all the good competitors arrive before the poor competitors, the distribution of each class conforms to the input matching rule. When competitors arrive in a random sequence, poor competitors switch between patches. Resulting distributions are compared with predictions from the ideal free distribution with unequal competitors and from statistical mechanics. The comparisons show fewer animals using the site with the highest resource than predicted by the input matching rule, that is, undermatching is found. The effect of each animal having a unique competitive ability is then examined. We discuss the application of ideal free distribution models to areas of behavioural ecology other than foraging, together with alternative rules to the standard instantaneous intake rates rule. Copyright 1998 The Association for the Study of Animal Behaviour.
RESUMO
Copyright 1998 Academic Press Limited
