Proboscis monkeys are endemic to Borneo and among the most distinctive primates, recognised by their pendulous noses. Their dependence on coastal mangrove and riverine forest makes them acutely vulnerable to habitat conversion.
Proboscis monkey welfare is overwhelmingly shaped by habitat loss. These animals are forest specialists that cannot survive in fragmented or degraded landscapes — they require large continuous areas of mangrove, riverine forest, and secondary forest connected by river corridors. As habitat shrinks, remaining groups are pushed into smaller fragments where food resources are depleted and intragroup competition increases, lowering subordinate individual welfare. Road crossings and river barriers isolate populations, disrupting natural group dynamics and reducing genetic diversity. In captivity, proboscis monkeys are notoriously difficult to maintain — their specialised gut fermentation system means inappropriate diets cause rapid health failure, and most captive individuals historically survived only months.