Laboratory animals housed in barren, isolated conditions experience welfare deficits that affect both their wellbeing and experimental validity. Enriched housing benefits both animals and science.
Laboratory animal housing welfare reflects a tension between standardization and behavioral need. Barren standard caging was historically justified on grounds of reducing environmental variability in experiments, but research increasingly shows that stress from inappropriate housing conditions creates its own experimental artifacts — immune dysregulation, altered hormone profiles, and abnormal behavior — that compromise rather than enhance scientific validity. Providing nesting material, shelter objects, and social housing for gregarious species improves welfare while producing animals whose baseline physiology more closely resembles a normal state. The implementation gap between welfare guidelines and actual practice in many facilities reflects cost and inertia rather than scientific necessity.