Proboscis monkeys are among the most specialized and difficult primates to maintain in captivity, with complex dietary and social needs.
Proboscis monkey welfare in captivity presents extraordinary challenges rooted in their dietary specialization. Their ruminant-like digestive system is adapted for a diet of specific leaves, unripe fruits, and seeds that are difficult to source and replicate in non-Bornean environments. Feeding inappropriate diets causes severe digestive problems. The extreme difficulty of maintaining these animals in good health means that proboscis monkey captivity programs are justified only in facilities with demonstrated success in dietary management and specialist primate care. For most facilities, the honest welfare assessment is that these animals cannot be adequately cared for in captivity and their conservation is better served by in-situ habitat protection.