Mice and rats are the most commonly used laboratory animals, accounting for over 80% of all animal research procedures, with significant welfare improvements achievable through environmental enrichment, social housing, and refined procedures.
Laboratory mice and rats in standard housing experience chronic welfare deficits from inadequate social contact, environmental complexity, and opportunity to express natural behaviors. These welfare problems are not merely ethical concerns but also scientific ones, as chronically stressed animals produce research results that may not generalize to natural conditions. Enriched housing and social management improve both welfare and research validity. The implementation of 3Rs principles has improved welfare significantly in countries with strong regulatory frameworks, but global standards remain inconsistent.