Laboratory mice and rats are the most numerous research animals globally. Environmental enrichment significantly improves their welfare while also improving research validity.
Laboratory rodent enrichment is one of the clearest cases where welfare improvement and scientific quality align. Barren housing environments cause chronic stress, abnormal repetitive behaviours, and altered physiology that compromise research validity. Providing nesting material, shelters, gnawing materials, and opportunities for social interaction significantly improves welfare while producing more physiologically normal animals. Regulatory frameworks including EU Directive 2010/63 require consideration of enrichment for all laboratory animals. Implementation varies but is improving. Group housing of social species like mice and rats is a welfare imperative, though aggression management requires skill and attention. Investment in rodent welfare is investment in better science.