Rats are intensely social animals whose welfare is severely compromised by solitary housing, yet single housing remains common in research settings despite evidence of harm.
Solitary housing of laboratory rats represents a significant and largely unnecessary welfare harm. Rats deprived of social contact show measurable physiological and behavioral signs of chronic stress — elevated corticosterone, impaired immunity, increased self-grooming and repetitive behaviors. The scientific case against isolation is as strong as the welfare case: stressed, isolated animals are physiologically different from group-housed animals in ways that affect experimental outcomes. Providing compatible cage mates resolves both problems simultaneously. Resistance to social housing often reflects convenience rather than genuine scientific necessity.