The logic of divisively asymmetric contests - respect for ownership and the desperado effect

Abstract. It is current orthodoxy in biological game theory that in animal contests with easily recognized asymmetries between the contestants, an asymmetry will be used to settle the dispute. Here it is argued that, if the winning of contests plays a major part in gaining reproductive success, an individual will not be selected to respect an asymmetry which will place it always in the losing role. Asymmetries that create consistent losers of this sort are termed divisive asymmetries. Divisive asymmetries cannot be used to settle important contests in an evolutionarily stable way because the consistent losers will have no incentive to respect them

A state-free optimization model for sequences of behaviour

The view of animals as optimizers is extremely important in many parts of biology, and is represented in a variety of theoretical models. Current developments in animal welfare create a need for a new theoretical model, which treats the animal as acting optimally in its choice of a sequence of behaviours, and places as few restrictions as possible on what quantity is being maximized. The intention is to facilitate the study of what the animal chooses, which will often be relevant in considering animal welfare. Currently, economic models of the consumer are borrowed in this situation, but they are not well suited for the increasingly exact analyses being performed. A new alternative model is presented here analytically in general, and a special case is studied numerically. The model does not attribute internal states to the individual, which is a simplification with advantages and disadvantages. © 2002 The Association for the Study of Animal Behaviour The use of economic analogies has been a major technique in animal welfare since it was introduced 20 years ago by Dawkins (1981), and recently the applications have become more and more quantitative (for example Cooper & Mason 2000; Mason et al. 2001). Th