Rats and mice make up approximately 95% of all laboratory animals used in biomedical research, yet their welfare receives less public and regulatory attention than primates or larger species despite their demonstrable capacity for suffering.
The welfare paradox of laboratory rodents is that the species most commonly used in research also receive the least public welfare attention and some of the least enriched environments. The scale is enormous: the suffering of individual mice and rats in bare cages, subjected to invasive procedures, is multiplied across hundreds of millions of individuals annually. Refinement — improving conditions and procedures to reduce suffering — offers significant welfare gains that do not compromise scientific validity. Evidence now clearly shows that enriched housing improves animal welfare without systematically confounding results, and many research councils now mandate minimum enrichment standards. The gap between what welfare science recommends and what most facilities provide remains substantial.