Dominance hierarchy

Dominance hierarchy arises when members of a social group interact, often aggressively, to create a ranking system. In social living groups, members are likely to compete for access to limited resources and mating opportunities. Rather than fight each time they meet, relative relationships are formed between members of the same sex. These repetitive interactions lead to the creation of a social order that is subject to change each time a dominant animal is challenged by a subordinate one.

This manifestation of intrasexual conflict can be observed in one of two systems. The social order can be either egalitarian or despotic. In a linear ranking system (often referred to as a pecking order), every member of the gender is recognized as either dominant or submissive relative to every other member, creating a linear distribution of rank. For example, groups of spotted hyenas and brown hyenas both demonstrate linear dominance. In a despotic system, one member is considered dominant while all other members of the living group are equally submissive. Examples of despotic social systems are found in meerkats, wolves, male gorillas, Neolamprologus pulcher, and African wild dogs.

Patterns of animal conflict reveal important insights into the evolution of behavior and the influence of behavior on relationships that develop in a social group. Pair-wise interactions have been observed to promote social hierarchies within groups of animals where individuals with successful agonistic behaviors often achieve dominance. These behaviors, which include aggression, threats displays, and fighting, are indicative of competition over resources, such as food or mates. However, they may vary based on the situation and position of the individuals involved.

Animal decisions regarding involvement in conflict are defined by the interplay between the costs and benefits of agonistic behaviors. When initially developed, game theory, the study of optimal strategies during pair-wise conflict, was grounded in the false assumption that animals engaged in conflict were of equal fighting ability. Modifications, however, have provided increased focus on the differences between the fighting capabilities of animals and raised questions about their evolutionary development. These differences are believed to determine the outcomes of fights, their intensity, and animal decisions to submit or continue fighting. The influence of aggression, threats, and fighting on the strategies of individuals engaged in conflict has proven integral to establishing social hierarchies reflective of dominant-subordinate interactions.

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