Social housing of laboratory animals where scientifically appropriate is one of the most impactful welfare improvements available, reducing chronic stress and improving research validity simultaneously.
Isolating social laboratory animals in individual cages was long justified by concerns about fighting and infection control, but evidence now strongly shows that the welfare and scientific costs of isolation exceed these risks for most species and protocols. Mice and rats isolated from conspecifics show elevated baseline corticosterone, altered pain sensitivity, and behavioral changes that introduce significant variability into research data. Social housing with appropriate environmental enrichment improves welfare and the quality of the science simultaneously.