Proboscis monkeys are endangered Bornean primates with highly specialized dietary and social needs that make ex-situ conservation extremely challenging.
Proboscis monkeys are one of the most difficult primate species to maintain in captivity. Their complex gut microbiome requires a strictly controlled leaf-based diet — feeding starchy foods or fruit in excess can cause fatal gastrointestinal fermentation. Social structure is rigid; harem groups require large, complex enclosures. Aquatic access is highly enriching given their natural riverine lifestyle. Few zoos outside Southeast Asia attempt to house them, and breeding success is very rare. Conservation efforts are therefore best focused on habitat protection in Borneo rather than captive breeding programs.