Proboscis Monkey (Nasalis larvatus)


Family:                    Cercopithecidae.

Status:                     Endangered.

Size:                        Length 1.5 to 2 ft., weight 15 to 50 lbs.

Diet:                        Herbivore.

Characteristics:        Social, easy-going.

Area:                       Borneo.

Offspring:                One.

Predators:               Crocodile, clouded leopard, man.



·       The male can make a loud honking sound with his large noise, to warn off predators.

·       When the group leaves sleeping trees, the males are usually the last ones to depart.

·       When sitting in trees, proboscis monkeys usually hang their tails downward for balance.



Proboscis monkeys live in groups of up to 40 individuals. Some groups are single male harems, in which there are approximately seven females for every one male.  Males who don’t have their own harem live in all-male groups. They’re very social animals and show affection by grooming each other, using both their hands and teeth. Males are very protective of their females and juveniles. Males are much larger than females, and have large, elongated noses. They have reddish-brown hair on their heads and backs, and silvery-gray hair on their limbs and under parts. Proboscis monkeys mostly eat leaves, especially pedada leaves, but may also dine on fruit, seeds, and flowers. Because they eat mostly leaves, they have specialized stomachs divided in several parts to be able to digest their leafy diets, and because of that, they have large, round bellies. They move about on all fours, and are excellent swimmers (they have partially webbed feet), but are extremely careful when entering the water, because they’re preyed upon by crocodiles. Usually they remain concealed high up in heavily leaved trees, where they can’t be seen or easily reached by predators. They’re active early in the morning, then rest during the hottest part of the day, and come out again to forage in late afternoon. Their favourite trees to sleep in are the pedada, the dungun and the pisang-pisang. They usually move from tree to tree, rarely using the same tree two nights in a row.



The proboscis monkey can only be found on the island of Borneo, in mangrove forests and in lowland rainforests, no more than 600 metres at most, and usually less than 15 metres from a river or stream. They shy away from areas where there is human settlement, except for one area along the Menanggol River, where they’ve become used to the presence of humans. At last count, there were only 7,000 proboscis monkeys left in Borneo, but the numbers are declining rapidly despite the fact that they are protected by the government. Logging in the areas where they live has resumed, further reducing their home areas, and as a consequence, there has been a continuous decline in population. Proboscis monkeys have shown very poor survival rates in zoos and wildlife sanctuaries, and often have much shorter lifespans than proboscis monkeys in the wild.



Mating can take place at any time during the year, but females, who initiate mating, wait until food supplies are plentiful. They give birth after a 166-day pregnancy. The baby has a blue face that lightens after two months to a dark gray, and by one year, the face begins to take on the pink colour of an adult. The baby stays close to its mother for one year, then becomes more and more independent. At about 18 months, males leave to join all-male groups. Females usually stay with the group they were born into. The lifespan of a proboscis monkey is 13 years.