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Proboscis monkey
Nasalis larvatus


CITES: Appendix I (What is CITES?)
IUCN Red List: N. larvatus: EN (What is Red List?)
Key: EN = Endangered
(Click on species name to see IUCN Red List entry, including detailed status assessment information.)

Nasalis larvatus
Photo: A. S. Clarke

It is very difficult to keep proboscis monkeys in captivity and few zoos have been successful. However, with very careful husbandry, it is possible keep proboscis monkeys in captivity and thus there is potential for ex situ conservation (Agoramoorthy et al. 2004). Proboscis monkeys are particularly threatened because one of their preferred habitats is coastal lowland forests, locations which are also often preferentially developed or cultivated by people. In sum, most of their habitat is threatened or already disturbed (Sebastian 2000). Compounding the problem, most proboscis monkeys are found outside of protected reserves (Boonratana & Sharma 1992).


Threat: Human-Induced Habitat Loss and Degradation

As with many primate species, habitat loss is a major threat to proboscis monkeys and much of their former habitat has already been lost (Bennett 1988; Boonratana & Sharma 1992; Sebastian 2000). In addition, extensive proboscis habitats are being targeted for development, as is the case in Central Kalimantan, Indonesia (Meijaard & Nijman 2000a). Human land use, including clearance for agriculture, plantation development (including for coca and oil palm production), mining, for human resettlement and for industrial sites, as well as burning, swamp reclamation, commercial aquaculture (fish and shrimp farming), and logging destroys habitats and also isolates populations from one another (Bennett 1988; Boonratana & Sharma 1992; Yeager 1992a; Sebastian 2000; Meijaard & Nijman 2000a; Soendjoto 2004; Agoramoorthy 2007). These problems are also made worse by access roads, which fragment populations and increases inbreeding (Soendjoto 2004). Also, many plantations have electric fences around them, which may prevent normal proboscis monkey ranging (Boonratana & Sharma 1992). Selective logging sometimes destroys preferred sleeping and feeding trees (Yeager 1992a). After logging, forests are sometimes poisoned to prevent undesirable vegetation from regrowing with the goal of increasing timber productivity as the forest regenerates. This likely affects proboscis monkeys adversely and prevents them from living in those habitats (Bennett 1988). In addition, human immigration from other areas is increasing land use and other sources of disturbance (Sebastian 2000).

Threat: Harvesting (hunting/gathering)

In some areas, proboscis monkeys are persecuted as crop raiders and are poisoned. In some regions, they are hunted for food, and in others, they are hunted recreationally, and as bait or feed for lizards, snakes and crocodiles (Bennett et al. 1987; Bennett 1988; Boonratana & Sharma 1992; Meijaard & Nijman 2000a; Soendjoto 2004). Hunting has already significantly reduced proboscis monkey numbers at some localities (Meijaard & Nijman 2000a). Also, even though they might not be the target species, firearm hunting of other game has the potential to disturb proboscis monkeys and alter their behavior (Tuen & Pandong 2007). However, hunting for food and persecution as crop pests is not always the case, as local Muslim inhabitants will not eat monkey meat for religious reasons (Boonratana & Sharma 1992). Proboscis monkeys are also kept illegally as pets (Meijaard & Nijman 2000b). Their sleeping habits near rivers also make them especially susceptible to hunting from boats (Tuen & Pandong 2007).

Threat: Pollution

In riverine areas of increased human activity, pollution may increase, especially due to spilled oil and fuel from boats, but also from human septic waste (Yeager 1992a). All of these types of pollution have the potential to alter proboscis monkey habitats.

Threat: Natural Disasters

Natural droughts increase the susceptibility of proboscis monkey habitats to destructive fires (Yeager 1992a).

Threat: Human Disturbance

Summertime activities of humans, such as fishing, fish-salting and smoking, trapping, and encampments, all disturb proboscis monkeys, keeping them away from preferred areas along rivers. Other activities that also disturb proboscis monkeys include rattan collection, the collection of honey from bees, and firewood gathering (Sebastian 1994 cited in Sebastian 2000). Further, increasing boat traffic, sometimes as a result of gold extraction along rivers, disturbs proboscis river crossing behavior and causes declines in population density and group size. Also, increased boat traffic threatens proboscis monkeys due to the potential for collisions while they are crossing rivers (Yeager 1992a). In Sabah, some proboscis monkey populations are threatened by unmanaged tourism (Ramesh Boonratana pers comm.).





Content last modified: February 25, 2009

Written by Kurt Gron. Reviewed by Ramesh Boonratana.

Cite this page as:
Gron KJ. 2009 February 25. Primate Factsheets: Proboscis monkey (Nasalis larvatus) Conservation . <>. Accessed 2020 July 6.