Mice and rats constitute over 95% of research animals used globally, yet their welfare needs including social housing and environmental enrichment are frequently not met.
Laboratory rodent welfare improvements benefit both the animals and the research. Chronically stressed mice produce variable cortisol responses that introduce experimental noise. Providing nesting material, shelter, and species-appropriate social housing reduces baseline stress and improves reproducibility. The welfare and scientific cases for better rodent housing are mutually reinforcing.