Drills are among the world's most endangered primates and among the least known. Their large social groups, complex hierarchies, and forest-adapted behaviours require sophisticated zoo management.
Drill welfare in zoos reflects both the challenges of managing large social primates and the conservation urgency that makes captive management so important. Their social complexity — dominance hierarchies, coalition dynamics, and male-male competition — requires large groups with stable long-term composition and ample space for subordinates to avoid dominant individuals. Small captive groups cannot replicate natural social richness, making enrichment that stimulates cognitive engagement especially important. Foraging enrichment across large substrate areas, puzzle feeders requiring tool-like manipulation, and novel olfactory stimuli engage drill intelligence and reduce frustration. Male colouration — which intensifies under positive hormonal conditions — provides a visible welfare indicator: brightly coloured males in stable social positions are more likely to be welfare-positive individuals. Conservation significance is paramount: every drill born in captivity has potential conservation value given their extreme wild rarity, making welfare investment in reproductive success directly conservation-relevant.