Proboscis monkeys have highly specialised digestive and dietary needs that make their successful captive management extremely challenging.
Proboscis monkey welfare in captivity illustrates the limits of zoo keeping for highly specialist species. Their digestive physiology is so tightly adapted to a specific leaf diet that dietary errors cause acute, potentially fatal bloat. The challenge of providing appropriate fresh foliage consistently has meant most attempts to keep proboscis monkeys outside their native range have failed. Their welfare needs cannot be met by most facilities. Conservation of this Endangered species must primarily occur through wild habitat protection — specifically the Borneo lowland forests they depend on. Zoos that cannot genuinely meet welfare needs should not attempt to keep this species.