Laboratory mice are the most commonly used research animals, and enrichment provision significantly affects their welfare and the validity of research conducted using them.
Laboratory mouse welfare represents a welfare issue at extraordinary scale: hundreds of millions of mice used in research annually, with welfare conditions varying dramatically between institutions. The welfare case for environmental enrichment is exceptionally well-supported scientifically - enriched mice show reduced stereotypy, lower stress hormones, and healthier behavioral profiles. Critically, enriched housing also improves research data quality by reducing baseline stress that confounds experimental results. This creates a rare alignment between welfare improvement and research quality improvement that should accelerate enrichment adoption. Yet many facilities still house mice in barren cages without nesting material or shelter, representing both a welfare failure and a research quality compromise.