Pigs are highly social animals with complex social needs that are frequently denied in intensive production systems, causing psychological stress and behavioral abnormalities in billions of animals.
Pig social lives are rich and their welfare is profoundly affected by social conditions. Stable groups with consistent membership allow pigs to form bonds and maintain clear social relationships with lower conflict. The intensive practice of mixing unfamiliar pigs during transport, at weaning, and at farm transfers imposes repeated acute stress as hierarchies are violently re-established. Pigs empathize with distressed companions — studies show physiological stress responses in pigs observing stressed conspecifics — meaning that poor welfare in one animal radiates distress through the group. Meeting pig social needs requires stable group management, adequate space, and enrichment.