Mice are the most widely used laboratory animals globally — their welfare needs and the improvements achievable in research settings.
Laboratory mouse welfare improvements are among the most impactful investments available in reducing research animal suffering, both because of the number of animals affected and because of the alignment between welfare improvement and scientific validity. Mice in chronic stress from individual housing, barren environments, or aversive handling have altered immune systems, endocrine profiles, and behavioral phenotypes that confound experimental results and reduce reproducibility. The science supporting enrichment, social housing, and tunnel handling is robust and consistent. The barriers to implementation are primarily institutional inertia and the incorrect assumption that enrichment adds variability to experiments — it does not, and typically reduces it by lowering chronic stress baseline variability.