Mice are the most widely used laboratory animals globally. Improving their welfare through the 3Rs framework — Replace, Reduce, Refine — is both an ethical imperative and scientifically beneficial.
The welfare of laboratory mice matters both ethically and scientifically. Stressed, understimulated mice show altered physiology and behaviour that can confound experimental results — meaning poor welfare is not just an ethical problem but a scientific one. Key welfare improvements include providing nesting material (which mice prioritise over food when cold), group housing for social species, reversal of lighting cycles to match natural activity patterns, and refined handling techniques that reduce fear. Pain assessment in mice has historically been poor — the Mouse Grimace Scale now allows standardised assessment of facial pain indicators. The principle of using the minimum number of animals needed for valid science, combined with meaningful enrichment, represents the current gold standard in laboratory mouse care.