Laboratory rats are the most commonly used research animals after mice. Their welfare depends on appropriate pain assessment, social housing, and environmental enrichment that supports natural behavior.
Laboratory rat welfare reflects the tension between scientific requirements and animal welfare obligations. Social isolation — historically common for experimental control purposes — causes significant stress in highly social rats. Evidence now shows that pair housing rarely compromises experimental validity while dramatically improving welfare. Pain assessment using the Rat Grimace Scale allows objective welfare monitoring during and after procedures. Enrichment provision including nesting material, tunnels, and shelter reduces stereotypic behaviors and stress indicators without significantly affecting most experimental outcomes. The 3Rs framework requires investigators to minimize the number of animals used, reduce suffering through better welfare practices, and replace animal models with alternatives where feasible.