[Abnormal behaviour with a focus on stereotypies--indicators of suffering and impaired welfare?]

Abnormal behaviour is a potential indicator of pain, suffering and injury in captive animals. Especially stereotypies, i. e. repetitive invariant behavioural patterns without obvious function or goal, can be observed as a consequence of inadequate housing conditions. Hence, they are often considered indicators of impaired welfare. In context of the ongoing scientific debate on captive animal welfare, the number of publications on stereotypies has increased, most notably in veterinary and farm animal research. Based on biological principles and definitions, we present several examples of stereotypic behaviour in (mainly) farm animals, and discuss approaches of preventing or reducing them. The occurrence of abnormal behaviour is often, but not necessarily, associated with the fact that modern housing and management precludes various evolutionary emerged highly motivated behaviours, or poses challenges the animals are unable to cope with adequately. Numerous studies show that stereotypies can be indicative of (current or past) suffering and impaired welfare. They can be avoided or at least reduced by increasing the biological relevance of the housing environments through environmental enrichment which stimulates species-specific behaviour.