Laboratory rat welfare depends critically on appropriate social housing and colony management, with isolated rats showing dramatically worse welfare outcomes than socially housed animals.
Laboratory rat social welfare illustrates how animal welfare and research quality can be aligned — socially housed rats are both better off and better research subjects. The stress physiology of isolated rats creates baselines that diverge from normal rat biology, introducing variability and artifacts into experimental results. Social housing requirements, now mandated in EU research regulations, represent a regulatory recognition that isolation is both a welfare harm and a research quality issue. Implementation has been uneven, and some facilities still justify isolation on scientific grounds that warrant scrutiny. The welfare case for social housing is strong and the scientific case against it is weak.