A monkey of riverine and coastal forests on Borneo. Males have conspicuously large noses.
Males are larger than females and have more protruding noses. Adults have reddish fur around the head and shoulders, with gray limbs and tails.
From 2022 to January 2025, researchers surveyed 18 sites across five districts of northwestern Sabah, Malaysian Borneo, in 30 boat surveys over 28 days. They saw proboscis monkeys at seven sites in 24 encounters, including repeat sightings; using each site’s highest count, they recorded at least 75 animals.
Sightings were limited to mangrove and riverine forests. Local reports extended known presence to 14 sites. The researchers described a patchy distribution with limited connectivity between groups.
IUCN Red List of Threatened Species · Endangered (EN) · Global
The 2021 global IUCN Red List assessment classifies the proboscis monkey as Endangered (EN) and records a decreasing population trend. It was last assessed on 21 November 2015. The assessment estimates a 70–75% population decline over three generations (36 years) and says hunting and habitat destruction continue to threaten most populations. The assessment is marked as needing an update.