Laboratory rats are highly social animals for whom solitary housing causes significant stress and welfare harm, with growing regulatory requirements for social housing wherever scientifically feasible.
Solitary laboratory rat housing causes measurable psychological suffering through chronic social deprivation. Isolated rats show increased anxiety, altered pain sensitivity, and impaired cognitive performance — ironically compromising the scientific validity of studies using these animals. Social housing with compatible pairs or small groups, enriched with appropriate nesting and hiding materials, dramatically improves rat welfare without compromising most research endpoints. Facilities resistant to social housing typically cite aggression risks that are manageable through proper pairing and husbandry protocols.