One of the costly and welfare-reducing problems in modern pig production is tail biting. Tail biting is an
abnormal behaviour, characterized by one pig’s dental manipulation of another pig’s tail. Tail biting can be
classified into two groups: the pre-injury stage, before any wound on the tail is present, and the injury stage,
where the tail is wounded and bleeding. Tail biting in the injury stage will reduce welfare of the bitten pig
and the possible spread of infection is a health as well as welfare problem. The pigs that become tail biters
may also suffer, because they are frustrated due to living in a stressful environment. This frustration may
result in an excessive motivation for biting the tails of pen mates. This review aims to summarize recent
research and theories in relation to tail biting.