Pig Social Behaviour: Understanding Group Dynamics for Better Welfare

Understanding pig social behaviour — dominance hierarchies, friendship bonds and aggression regulation — is essential for designing farming systems that minimise suffering.

Key Facts

Pigs establish stable dominance hierarchies through initial aggressive contests; once established, hierarchies reduce ongoing aggression
Introducing unfamiliar pigs causes significant aggression as hierarchy is re-established — a major welfare event
Pigs form strong preferential pair bonds with particular individuals within their social group
Stress from social instability (repeated mixing) elevates cortisol and reduces immune function
Space allowance significantly affects aggression: below 0.65m2 per pig, aggression increases non-linearly

Welfare Considerations

Mixing unfamiliar pigs is one of the most significant acute welfare events in commercial pig production. Each mixing event triggers hours to days of aggressive contests to re-establish hierarchy, causing wounds, stress and growth setback. Stable social groups maintained from weaning to slaughter dramatically reduce this welfare burden. Pigs within stable groups recognise companions individually and show preferences — demonstrating a social complexity that demands respect. Management systems that minimise mixing, provide adequate space, and maintain stable groups from birth are significantly more welfare-positive than those based on continuous regrouping.

What You Can Do

Choose pork from producers with demonstrated stable social group management policies
Support Farm Animal Welfare Council and CIWF guidance on minimum mixing events in pig production
Advocate for space allowance regulations to be updated based on pig welfare research rather than just industry economics
Learn about innovations in social group management that allow welfare-positive large-group systems
Engage with producers about the production efficiency benefits of reducing mixing-associated stress and injury