Mice are the most commonly used research animals globally; welfare improvements through enriched housing, group housing, and pain management have both ethical importance and research quality benefits.
Mouse welfare in research settings has improved substantially through the implementation of enrichment standards, but variability between institutions and countries remains significant. The evidence base showing that welfare improvements benefit research quality — by reducing stress-induced phenotypic variation — provides a scientific as well as ethical argument for better mouse care. Bare cages, social isolation, and inadequate nesting material are increasingly recognised as confounds that compromise both welfare and data quality.