The rare and unique Proboscis Monkey is found only in the coastal areas of Borneo, in mangrove and diterocarp forests and in the lowland rainforests near fresh water and rivers. Less than 3000 Proboscis monkeys remain today and they are fast on their way to extinction due to logging and deforestation.
This reddish-brown monkey has a large pot belly and a tail as long as its body, but its most distinctive feature is its long nose, giving it its unique appearance, as well as its name. The male Proboscis is much larger than the female, as is its nose, which often hangs down over its mouth.
The nose is a prominent feature in the primates’ life style. It stands out straight and acts as a resonator when the monkey vocalizes, making loud honking sounds when it senses danger, and pushing it aside in order to feed; it swells and turns red when the Proboscis is excited or angry, and it is a hindrance when the creature is wounded as it cannot lick itself clean.
Proboscis Monkeys depend on the mangroves near the rivers for resting and sleeping, so that they generally venture no further than 600 m. from the river’s edge. These specialized plant eaters feed only on young leaves from Borneo trees, seeds and green starchy fruits. Their unique digestive systems and are divided into compartments filled with cellulose digesting bacteria which enable them to digest leaves and seeds and neutralize toxins, and give them their pot belly appearance They are the only mid-sized mammal with this ability living in the forest’s canopy.
Living in groups averaging in size from 12-32 animals and sometimes as many as 60, Proboscis Monkeys have a unique two-level social system. One level includes all-male groups comprised of infant, adolescent and adult monkeys; a second level is made up of several groups of harems, each led by a separate male, who come together to form a troop. Since these monkeys are neither territorial nor aggressive, smaller groups join together to form larger troops that overlap in territory. They avoid deforested areas and human settlement.