Proboscis Monkey (Nasalis larvatus): Bio-ecology and Conservation

Abstract

Proboscis monkeys (Nasalis larvatus) are endemic to Borneo and primarily reside in peat swamp forest, mangrove, and riparian forest. Some smaller populations have also been found in upstream dipterocarp forest, as well as in rubber plantations, 300 km from coastal areas (Soendjoto 2003). Swamp forest along riverbank and riparian mangrove in the coast are also potential habitats for proboscis monkeys. The proboscis monkey population is very dependent on the quality of the wetland ecosystem, especially mangrove forest and riparian forest. This species’ focus on quality habitat makes it relatively intolerant to habitat disturbance (Bennett and Gombek 1993; Yeager 1992). McNeely et al. (1990) reported that there are 29,500 km² of proboscis monkey habitat. Since 1990, 49% of this habitat has been lost, and only 4.1% of this habitat occurs within designated conservation areas. Undoubtedly, as village settlements and agricultural areas along the river’s edge tend to increase, the proboscis monkey habitat will decline as will its population. The increasing frequency of river traffic, forest concession activity, forest fire, illegal logging, and conversion of swamp forest to plantation estate and agricultural land, or fishpond development at mangrove forest, all represent primary causes of proboscis monkey habitat destruction.

The degradation of proboscis habitat has occurred quite fast because most of it has high economic value to the people who reside in the surrounding riverbank. The community uses the river as a transportation line, while the riparian forest is used by people to open agricultural gardens and settlements. All of these behaviors cause destruction to proboscis monkey habitat. As a result, the population of proboscis has decreased, the distribution has become more spotty (increased distance between subpopulations) (Bismark and Iskandar 2002; Ma’ruf et al. 2005), and local people continue to view the proboscis monkey as a pest.