Environmental enrichment in zoos has evolved from an ad hoc practice to an evidence-based discipline, with research demonstrating which types of enrichment most effectively reduce stereotypy and promote positive welfare states.
Stereotypic behaviors - repetitive, functionless movements - develop in animals whose environments fail to meet their behavioral needs. Once established, stereotypies often persist even when conditions improve, indicating lasting neurological changes from early deprivation. Effective enrichment can reduce stereotypy expression and improve welfare indicators including stress hormone levels and positive behavioral states. The scientific study of enrichment has revealed that motivation matters: animals given control over their enrichment access show greater welfare benefits than those given passive enrichment. Zoos must evaluate enrichment outcomes rather than assuming novelty alone improves welfare.