Rats and mice constitute over 90% of laboratory animals used globally; social housing, environmental enrichment, and refined procedures dramatically improve their welfare.
Mice and rats form the vast majority of laboratory animals used in research, yet their welfare has historically received less attention than that of larger, more cognitively salient species. They are highly social, cognitively complex animals whose welfare needs extend far beyond mere physical health. Individual housing causes significant psychological distress including stress-related behaviors and altered physiology. The welfare improvements available through social housing, nest materials, and burrowing substrate are low-cost and well-evidenced. Applying the 3Rs with genuine rigor to rodent research, rather than treating mice as low-welfare consequence species, would transform the welfare of the largest group of laboratory animals.