Laboratory mice are the most commonly used research animal. Social housing policies have significant welfare implications that are now better understood and increasingly implemented.
Laboratory mouse social housing reform is one of the clearest welfare improvements in research animal science. Isolated mice show higher baseline stress, altered pain sensitivity, and abnormal behaviour - all of which are welfare concerns and potential confounders in research results. The evidence that social housing improves both welfare and research quality makes this a rare case where welfare and scientific arguments are perfectly aligned. The remaining challenge is managing male aggression in grouped housing, which requires careful attention to group composition, sufficient resources, and appropriately enriched environments.