Ritualized Conflict in Odontomachus Brunneus and the Generation of Interaction-based Task Allocation: a New Organizational Mechanism in Ants

Intracolonial conflict among ant workers can establish a reproductive hierarchy, with top-ranking individuals often securing oviposition opportunities. Here we show that in the ant Odontomachus brunneus, reproduction-based dominance interactions control worker movement and location, and that this, in turn, mechanistically governs task allocation within the colony and establishes a division of labour for nonreproductive tasks. Movement made by a worker towards the brood is mostly preceded by winning a pairwise dominance interaction, and movement away from the brood is mostly preceded by losing a pairwise interaction. Consequently, workers are distributed within the colony such that the more subordinate the individual, the more peripheral her location with respect to the reproductive centre of the nest. Behavioural roles are naturally restricted to particular zones of the colony, therefore, allocation to a particular zone, through dominance interaction, ensures role specialization. This represents a new organizational mechanism, which we call 'interaction-based task allocation'. In characterizing the dominance interactions of this species, we also identify two new behaviours: (1) 'subordinate driving', which involves a dominant individual physically manoeuvring a subordinate, by way of continued aggression, away from the reproductive centre of the nest; and (2) 'antennal shivering', which describes the antennal movements made by a subordinate immediately preceding and during subordinate driving. Copyright 1999 The Association for the Study of Animal Behaviour.