Laboratory mice are the world's most widely used research animal, and their welfare through environmental enrichment has major implications for both individual animals and the quality of research data.
Laboratory mouse welfare is both an ethical imperative and a scientific quality issue. Mice housed without nesting material, in bare cages without hiding opportunities, and in isolation from conspecifics experience chronic stress that alters their physiology, immune function, and behaviour - potentially introducing experimental confounds. Providing nesting material, shelters, and appropriate social housing produces mice with more normal baseline physiology that may actually improve research reproducibility. The welfare-science alignment is notable: reducing mouse stress is simultaneously the right thing to do and potentially better science. Regulatory requirements for enrichment are advancing, but implementation monitoring in research facilities remains inconsistent.