Stable hierarchical structures within groups of crayfish emerge from a series of dyadic encounters among its members. A modeling approach was used to explore the progression in fighting success of individual entities under different behavioral scenarios and the respective outcomes were fitted to empirical data. Changes in the relative magnitude of winner and loser effects influenced the divergence of hierarchical ranks: a few high-ranking despots rapidly emerged when winner effects were dominant, an excess of loser effects quickly produced individuals of distinctly low rank, while a balance of winner and loser effects produced a more gradual divergence of ranks. Comparison with empirical data from the formation of social group structure in crayfish indicated a greater importance for loser effects.