Laboratory mice are the most widely used research animals, and providing environmental enrichment through nesting material, shelters, and social housing significantly improves their welfare without compromising most research.
Laboratory mice in barren cages experience chronic low-level stress evidenced by elevated corticosterone, stereotypic repetitive behaviours, and impaired immune function. The welfare impact is often overlooked due to the small size of these animals. Providing nesting material, a shelter, and social housing is low-cost and dramatically improves welfare outcomes. Importantly, enrichment improves research quality in many paradigms by reducing stress-induced variability and improving physiological baseline. Regulatory minimum standards lag behind current best practice in many jurisdictions.