Proboscis Monkey (Nasalis larvatus)


Class: Mammalia
Order: Primates
Family:    Cercopithecidae
Size:    Length: 22 to 28 inches  (56 to 72 cm)
Weight: 15 to 53 pounds (7 to 24 kg)
Diet: Mainly leaves, but also fruit, seeds and flowers
Distribution: Borneo
Young:  1
Animal Predators:  Crocodiles, clouded leopards, pythons and false gavials
IUCN Status: Endangered
Terms: Group: Troop
Lifespan: 13 years in captivity, more in the wild



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

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


Males are much larger than females and have a large, elongated nose. Proboscis monkeys have reddish-brown hair on their head and backs, creamy hair on their chest and silvery-grey hair on their limbs and undersides. Because they eat mostly leaves, they have a specialized stomach that is divided in several parts to be able to digest their leafy diets, and because of that, they have a large, round belly. 



Proboscis monkeys can only be found on the island of Borneo in mangrove forests and in lowland rainforests, usually less than 16 yards (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 have become used to the presence of humans. 


Feeding Habits

Proboscis monkeys mostly eat leaves, especially pedada leaves, but may also dine on fruit, seeds, and flowers. 



Females initiate mating, which can take place at any time during the year. They give birth after a 166-day pregnancy. The baby has a blue face that lightens after two months to a dark grey, and by about 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 troop they were born into, although they may move from one group to another when they are young. 



Proboscis monkeys live in troops of up to 32 individuals. Some troops are single male harems, in which there are approximately seven females for every one male.Males who do not have their own harem live in all-male groups. They are 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. 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 are preyed upon by crocodiles. Usually they remain concealed high up in heavily leaved trees, where they cannot be seen or easily reached by predators. They are 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.



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.



Proboscis Monkey Wildlife Fact File, IM Pub, US