Maynard Smith and Price (1973) have shown that the methods and terminology of Game Theory can be used to study the evolution of various strategies in animal species. They write aij as the mean ‘value’ to the user of strategy i when his opponent uses strategy j; these values aij are related to the fitness of the user of i, in the sense that, if aij is large, it is advantageous to use strategy i when one's opponent uses strategy j, and this advantage will be reflected in an increase in one's reproductive potential. For example, these may be a contest for territory, or dominance rights.