Pigs are highly social animals with complex dominance hierarchies that create welfare challenges in farm management. Understanding pig social behaviour enables management decisions that reduce aggression, injury, and chronic stress in group-housed animals.
Pig social behaviour reveals both the sophistication of these animals and the welfare costs of management practices that ignore their social needs. The dominance hierarchy that pigs establish is not arbitrary aggression but a complex negotiation process that, once complete, creates a stable social environment with minimal ongoing conflict. The welfare problem arises when farm management disrupts these established hierarchies through repeated regrouping: each regrouping triggers a new round of fighting as hierarchy must be re-established, exposing all animals to injury and stress. Minimising regrouping frequency, creating stable groups from early life, providing sufficient space and enrichment to reduce competition, and matching animals by size are all evidence-based interventions that reduce the welfare costs of group management without compromising production.