It is expected that there would be different strategies employed by a population.

Game theory can derive this result. John Maynard Smith introduced the idea of a evolutionarily stable strategy. The idea is to use the classic game theory payoff matrix successively to determine a stable mix of strategies used by the population. Some payoff matrix aren't stable since one of the strategies can dominate the others and causing the dominated strategy to be extinct in the population.

http://en.wikipedia.org/wiki/Evolutionarily_stable_strategy

The types of strategy typically discussed are:

  * Doves (always peaceful)
  * Hawks (always attack)
  * Bully (feign attack)
  * Retaliator (peaceful until attacked)