Laboratory mice and rats are among the most numerous animals used in research. Environmental enrichment can dramatically improve their welfare with minimal impact on experimental outcomes.
Laboratory rodent welfare has improved significantly as evidence accumulates that enrichment benefits animals without compromising research validity. Nesting material is essential: mice without it show elevated stress hormones and cannot thermoregulate effectively. Social housing reduces isolation-induced distress, and pair or group housing is now recommended for most protocols. Running wheels, shelters, and gnawing materials satisfy key behavioral needs. Critics argued enrichment would increase experimental variability, but studies show enriched animals often produce more consistent data because their baseline stress is lower. Institutional animal care and use committees are increasingly requiring enrichment justification when it is withheld.