Evolutionarily Stable Strategies

The concept of the evolutionarily stable strategy, or ESS, is an important part of game theory. An ESS is a strategy which, over evolutionary time, is able to withstand the invention of new strategies. Although Maynard Smith and Price (1973) visualized strategies as being genetically encoded, this same logic applies to strategies which are learned during the course of an animal's life. In most models of the prisoner's dilemma the "tit for tat" strategy is evolutionarily stable; over time it can beat any other strategy that you might invent for this game.

Analyses of fighting behavior are particularly well suited for game theory analysis (Breed and Rasmussen 1980, Reichert 1984, 1996). In fights, each animal has clear-cut tactics which it can employ, and these can be analyzed as a series of interchanges within the fight. The choices of which tactic to play, when to escalate, and when to submit or flee are all moves in a game. Assessment of the opponent's strength, size, and commitment to winning the fight are important in many animal conflicts, and assessment can be included in the model.

In general, size and possession of a resource give a fighter considerable adavantages. Most studies of animal fighting show that the winner can be easily predicted by these factors. The effect of resource possession is somewhat surprising, as the resource (a territory, a mate, or a prey item) should have equal value to the two contestants. The holder of the resource may be not so much defending the resource itself as defending the previous effort put into gaining the resource and defending it. The ability of an animal to maintain possession of a resource is termed its resource holding power (RHP); measurement of RHP can give a way of comparing animals' prospects for winning contests.

Breed, M.D., Rasmussen, C.D. 1980. Behavioral strategies during intermale agonistic encounters in a cockroach. Anim. Behav. 28:1063-1069.

Crowley P H 2001 Dangerous games and the emergence of social structure: evolving memory-based strategies for the generalized hawk-dove game BEHAVIORAL ECOLOGY 12 (6): 753-760

Crowley P H 2003 Origins of behavioural variability: categorical and discriminative assessment in serial contests ANIMAL BEHAVIOUR 66: 427-440

Maynard Smith J, Price G R 1973 Logic of animal conflict. NATURE 246 (5427): 15-18

Riechert S E 1986 Spider fights as a test of evolutionary game theory AM SCI 74 (6): 604-610

Riechert S E 1984 Games spiders play 3. cues underlying context associated changes in agonistic behavior ANIM BEHAV 32: 1-15

Return to beginning of Chapter 1

Return to Table of Contents

page 15-*
copyright ©2003 Michael D. Breed, all rights reserved.