Chapter

Communication

Volume 12 of the series Perspectives in Ethology pp 179-224

Determinants of Conflict Outcomes

  • William J. HamiltonIIIAffiliated withDivision of Environmental Studies, University of California, Davis
  • , John W. McNuttAffiliated withWild Dog Research Project

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Abstract

Analysis of individual differences in competitive abilities is an essential part of the interpretation of unequal access to resources. Here we develop and apply a model applicable when dyadic contest outcomes determine access to resources, including mates. Individual differences in fighting ability may be decisive in determining contest outcomes. The components of fighting ability (FA) include inheritance (FAi), condition (FAc), experience (FAe) and development (FAd) to and throughout senescence (FAs). Present fighting ability (FAp) is a dynamic entity that varies as the value of these components change, waxing and waning as costs are incurred in contests. Fighting ability contributes to the probability that opponents will enter into and persist with patterns of conflict behavior and prevail as contest winners.

Simulations identify the probabilities of gaining access to status and resources when FA determines contest winners following dyadic contests. A sequence of interactions between opponents produce frequency distributions of fighting ability within populations which contain and may provide information to contestants about their fighting ability compared with that of other population members. Individual win:loss records may be incorporated into individual experience, resulting in effective behavioral responses to the probabilities of winning subsequent encounters. The probabilities of improving rank by transferring from one to another linear dominance hierarchy are determined given the assumption that FA determines rank. We identify the relationship of fighting ability to contests for resources in a competitive arena where some individuals are excluded from resources. These simulations emphasize the value of diachronic observations of individual contest histories and outcomes.

When fighting ability is not decisive in determining contest outcomes and the distribution of resources, the relative effect of other parameters in doing so is enhanced. The analysis of competitive behavior promotes identification of separable parameters which sometimes have opposing effects. Determinants of these additional processes occurring during animal conflict are identified and their utility in separating behavioral relationships is considered. These determinants include social support (S) from additional parties in contests and resource value (V), a collection of several relevant parameters influencing motivation. Motivation (M), the propensity of individuals to enter into and persist with contests, is a diversely used term. But the processes and phenomena it incorporates cannot be discarded, because without its role in the analysis of individual differences, fitness consequences of behavior are necessarily analyzed exclusively as a function of V.

Studies of the relationship of the determinants of conflict outcome identified here have been and can be incorporated into general models of contest behavior. To determine their respective effect upon conflict behavior and contest outcomes, some components of fighting ability can be set equal by experimentation or ordering of field observations. We extend our model to groups of individuals arranged in linear dominance hierarchies and to the ideal despotic distribution where access to resources is contested by many individuals. We make predictions about the exact probabilities of winning under alternative circumstances. We suggest how animals might adjust their behavior if they were to use the estimates of personal fighting ability identified by simulations to estimate their probability of winning.