Laboratory mice are among the most numerous research animals, and advances in environmental enrichment science are improving their welfare while also enhancing the scientific quality of research using them.
Laboratory mouse welfare is an area where welfare improvement and scientific quality are genuinely complementary rather than in tension. Enriched housing reduces chronic stress, normalizes immune function, and produces more representative baseline physiology - making research more translatable. Key enrichment advances include nesting and burrowing materials, housing complexity, social grouping management, and positive handling training. Progress has been substantial, but implementation varies widely across institutions. Full implementation of evidence-based enrichment standards could simultaneously improve the welfare of hundreds of millions of animals and the quality of biomedical research.