Which rainforest primate is endemic to the island of Borneo and has a famously enlarged nose?

The proboscis monkey is a Bornean rainforest primate famous for its enlarged nose.

Proboscis monkeys live only on Borneo, especially in mangroves, riverine forests, peat swamps, and other wet habitats. Adult males have much larger noses than females. Researchers associate the male nose with vocal communication and sexual signaling, although its precise acoustic effects are complex.

The monkeys eat leaves, shoots, seeds, and unripe fruit. Their digestive system is adapted to a foliage-heavy diet, but this also means they must avoid many chemically defended or highly ripe foods. They are capable swimmers, and their partially webbed fingers and toes help them cross waterways.

Proboscis monkeys are social and may form groups that join together in larger gatherings. Habitat loss, hunting, and fragmentation have reduced their numbers. Their restriction to Borneo makes them especially vulnerable to changes in coastal and lowland forests.