Non-human primates used in biomedical research are highly social animals whose psychological wellbeing depends on social housing, yet many remain singly housed due to institutional habit and perceived experimental constraints.
The psychological suffering of singly housed research primates is well-documented and represents one of the most serious welfare problems in biomedical research. Primates in isolation develop abnormal behaviors that reflect genuine psychological distress — self-biting, hair-pulling, stereotypic rocking — equivalent to responses seen in socially deprived human children. The scientific case for maintaining single housing in most research contexts is weak; most studies can be conducted with paired or group-housed animals. Institutional animal care committees have a critical responsibility to ensure that social housing is the default and that exceptions are rigorously justified.