Proboscis monkeys are remarkably specialist Borneo primates that have rarely thrived in captivity. Their welfare requirements make successful captive management exceptionally challenging.
Proboscis monkey welfare in captivity represents one of the clearest cases where the welfare cost of captivity is exceptionally high. Their dietary requirements — complex leaf fermentation chemistry, prohibition of simple sugars — are difficult to replicate in captivity and have historically caused high mortality. Their aquatic behaviour, riverine habitat needs, and complex social structure add to the challenges. The welfare case for captive proboscis monkey holding is poor — conservation value is limited because successful reintroduction requires intact riverine forest, and welfare costs are high. Conservation investment is better directed at protecting remaining Borneo forest habitat.