The proboscis monkey is characterized by a pot belly and an unusually large, bulbous nose that scientists believe helps amplify its sounds during reproduction and danger. While the nose of the male hangs down over its mouth, the females have significantly smaller noses.
The proboscis monkey lives almost entirely on Borneo, an island in Malaysia in southeast Asia. This species inhabits the jungle, where it dwells among the treetops. The monkey's main food sources are leaves, seeds and unripe fruit. Occasionally, the monkey leaves the trees to collect fruit from the ground. The proboscis monkey only eats unripe fruit because the fermentation and bloating resulting from digesting ripe fruit can cause its death. The monkey is able to digest fibrous leaves because of the two-chambered stomach located in its pot belly. This stomach is filled with bacteria especially adapted to digesting the cellulose found in leaves.
The proboscis monkey is one of the largest species in Asia, reaching a height of up to 28 inches and a weight of up to 50 pounds. However, the females are significantly smaller, reaching only half the size of their male counterparts. As of 2014, this species is endangered. Habitat loss and hunting have caused the population numbers to drop.