Proboscis monkey

Proboscis monkey

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. This species is restricted to lowland habitats that may experience tides. It favours 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 20 m (66 ft) 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.

In Sabah, Malaysia, proboscis monkeys have been observed in mixed-species groups with silvery lutungs, and interspecific mating and a possible hybrid has been observed. Researchers believe this may be a result of the two species being confined to a small patch of riverine forest due to deforestation in order to plant oil palm trees.

Proboscis monkeys are known to make various vocalizations. When communicating the status of group, males will emit honks. They have a special honk emitted towards infants, which is also used for reassurance. Males will also produce alarm calls to signal danger. Both sexes give threat calls, but each are different. In addition, females and immature individuals will emit so-called "female calls" when angry. Honks, roars and snarls are made during low-intensity agonistic encounters. Nonvocal displays include leaping-branch shaking, bare-teeth open mouth threats and erection in males, made in the same situations.

My Sincere thanks to Fr Rayappa Kasi for help with the footage.