Mice and rats account for over 95% of animals used in biomedical research, yet their welfare remains inadequately protected compared to larger laboratory species.
The sheer scale of mouse and rat use in research means that even small improvements in their housing and handling standards would benefit enormous numbers of animals. Yet mice in particular lack the welfare protections extended to larger species — they were excluded from the original US Animal Welfare Act, and standards for their housing lag behind their actual behavioral and social needs. Evidence-based improvements like larger, more complex housing, social housing for social species, and positive handling training can improve their welfare substantially without compromising research quality.