Abstract/Summary

Brokerage typologies represent an aspect of sociality by describing the social structure, at a group and individual level, concerning the direction and flow of behaviours or information within, and between subgroups. While animal studies have identified keystone individuals, capable of imparting positive and negative effects on conspecifics, none have characterised social networks based upon brokerage roles. This study applied a brokerage model to a dynamic breeding sow herd (average size = 78) to investigate the direction aggression flows within and between subgroups (based upon connectedness). In total, 42 h of video observations were obtained over two production cycles. Each production cycle covered 21 days, and behavioural observations occurred on days 1, 2, 3, 7, 14, 20, 21. The social network metrics of degree centrality (number of interactions) and brokerage position (the extent to which individuals lie on the directed path between two previously unconnected individuals) were analysed to describe the directional flow of agonistic behaviours within the networks and investigate the relationship between sociality and brokerage typology. Brokerage typologies are described as coordinators, gatekeepers, representatives, consultants, and liaisons. Aggressive behaviours included biting, thrusting, chasing, and displacement. The results revealed all pigs have brokering capability regardless of social connectivity, with a relationship between the level at which a sow is interacting and the brokerage typology they typically engage. Coordinating and consulting behaviour was typically engaged in by the highest connected sows. Significant differences in initiated behaviour (outdegree centrality) and received behaviour (indegree centrality) were found between the specific brokering roles in both production cycles, with coordinators found to be the most aggressive individuals in both networks. Results also reveal a consistency in group-level structure over two production cycles with further consistency in individual behaviour by coordinators and consultants. This preliminary study of brokerage types in a dynamic sow herd demonstrates the capacity to extend the traditional social network metrics currently applied in animal science research. It further provides an individual-level criterion to describe how behaviour is enabled to flow through a network.