Rats are the most widely used mammals in biomedical research, yet their complex social and cognitive needs are frequently underserved by standard housing conditions, creating both welfare and scientific validity concerns.
Rat welfare in research has improved considerably with recognition that stress from poor housing confounds experimental results. The 3Rs framework calls for refinement of housing to include appropriate social groups, enrichment, and larger spaces. Many research institutions now provide pair or group housing, nesting material, hiding places, and play opportunities. However, implementation is inconsistent globally, with significant welfare variation across laboratories.