Primates have the most complex social needs of any zoo animals, and appropriate social housing is the most important determinant of captive primate welfare across all species.
Primate social welfare cannot be compromised without causing serious psychological harm. Unlike many zoo species where solitary housing is merely suboptimal, social isolation in primates causes genuine psychological suffering manifesting as self-injurious behavior, depression, and stereotypies. Species-appropriate social grouping is therefore the non-negotiable foundation of primate welfare. This is particularly relevant for the UK's private primate trade, where marmosets and capuchins are kept as companions with no social contact of their own species - a practice that causes documented welfare harm and is under increasing regulatory scrutiny.