Laboratory animal housing has evolved significantly, with growing evidence that social housing and environmental complexity are essential welfare requirements, not optional extras.
Laboratory animal housing standards have improved dramatically over the past three decades, driven by the 3Rs framework and growing understanding of social species' needs. The shift from isolated to social housing for mice and rats is one of the most significant welfare improvements in laboratory animal science: isolation-housed rodents show chronic stress, immunosuppression, and behavioural abnormalities that compromise both their welfare and research validity. Environmental complexity - nesting material, running wheels, hiding structures - provides cognitive and physical stimulation that maintains behavioural health. The welfare and scientific arguments align: stressed, socially deprived animals produce noisy, poorly reproducible data. Better housing is both a welfare and a scientific quality imperative.