The proboscis monkey (Nasalis larvatus) is one of the strangest and most recognisable primates on Earth. The adult male's enormous, pendulous nose can exceed 10 cm — it amplifies his calls and is thought to attract females. You will find them almost nowhere outside Borneo, and within Borneo, Bako National Park offers some of the most reliable sightings in the world.
Proboscis monkeys are semi-aquatic, which is unusual for primates. They are strong swimmers — even crossing rivers — and their webbed feet make them more agile in water than on land. At Bako, they congregate in the mangroves and nipah palms near the park jetty each evening before dusk, descending to drink and socialise. The best viewing spot is the mangrove boardwalk at Telok Assam, where troops gather at 17:00–18:00 most days.
Their diet is almost exclusively leaves, unripe fruit, and seeds — a specialised gut with a chambered stomach neutralises the plant toxins that would sicken other primates. You can recognise females and juveniles by their smaller upturned noses and slate-blue faces at birth that gradually turn grey. A resident troop of roughly 50 individuals ranges across the park's coastal mangrove fringe, and a second troop inhabits the Lintang Trail area — walk the Lintang loop at dawn for your best inland sighting.
Proboscis monkeys are classified as Endangered on the IUCN Red List. Their population has declined by more than 50% over the past 40 years due to mangrove deforestation and hunting. The protected land inside Bako is one of the few refuges where the species can persist. Park rangers ask visitors to maintain a 5-metre distance and never feed them — human food disrupts the specialised bacterial flora in their stomachs, often fatally.
If you visit only once, choose the late afternoon. Position yourself on the jetty pier or the first section of the mangrove trail by 16:30 and wait. Entire troops — sometimes 20 or more animals — come crashing through the canopy to roost at the forest edge as the sun drops below the South China Sea. Also watch for silver leaf monkeys in the same area; the two species often share the same trees without conflict.