Mice and rats comprise the vast majority of laboratory animals. Applying the Three Rs — Replacement, Reduction, and Refinement — meaningfully improves their welfare while maintaining scientific value.
Laboratory rodents are sentient animals capable of pain, fear, and suffering. Many experience significant welfare deficits: barren housing, social isolation, invasive procedures, and experimental disease. The normalization of these conditions in research can lead to insufficient attention to refinement opportunities. However, improving rodent welfare is not just an ethical imperative — it is also scientifically beneficial. Stressed, isolated animals in barren environments show different physiological baselines and experimental responses than healthy, socially housed animals, reducing the translational value of research. Enriched housing, social grouping, and refined procedures improve both welfare and the quality of the science, making this one of the clearer cases where ethics and efficacy align.