The proboscis monkey is endemic to the island of Borneo and can be found on all three nations that divide the island: Brunei, Indonesia and Malaysia. It is most common in coastal areas and along rivers.Bennett E. L., Gombek F. (1993) Proboscis monkeys of Borneo. Sabah (MY):Koktas Sabah Berhad Ranau. This species is restricted to lowland habitats that may experience tides. It favors dipterocarp, mangrove and riverine forests. It can also be found in swamp forests, stunted swamp forests, rubber forests, rubber plantations, limestone hill forests, nypa swamps, nibong swamps, and tall swamp forests, tropical heath forests and steep cliffs. This species usually stays within at least a kilometer from a water source. It is perhaps the most aquatic of the primates and is a fairly good swimmer, capable of swimming up to underwater. It is known to swim across rivers. Aside from this, the proboscis monkey is largely arboreal and moves quadrupedally and by leaps. It is known to jump off branches and descend into water.
