Mice account for over 60% of all laboratory animals used worldwide, yet their welfare is often overshadowed by debates about more charismatic species. Understanding mouse needs matters enormously at this scale.
Mouse welfare improvements often seem minor in isolation but are transformative at scale. Providing deeper bedding, nesting material, and social housing costs little and dramatically improves welfare outcomes. Replacing CO2 euthanasia with isoflurane or cervical dislocation reduces suffering at the moment of death. Cage enrichment — tunnels, shelters, gnawing material — allows expression of species-typical behaviour. These refinements do not compromise scientific validity and are increasingly recommended by major research bodies.