Decline in proboscis monkeys

Sabah’s proboscis monkey populations are declining due to habitat loss as riparian forest are continually destroyed to plant oil palm and mangrove areas reclaimed for development. Images courtesy of Rudi Delvaux/DGFC/SWD.

University researchers and conservationists in Sabah have shown that proboscis monkey populations throughout Borneo may experience population decline if nothing is done to stop their habitat degradation.

The study, carried out by the School of Biosciences & the Danau Girang Field Centre, the Sabah Wildlife Department (SWD), and Oxford Brookes University with researchers from Indonesia is published in the scientific journal Endangered Species Research.

Proboscis monkeys are mainly confined to peat and freshwater swamp forests, mangrove forests, and lowland dipterocarp (riverine) forests, habitats which are the most threatened in Borneo because of logging and conversion of land for agriculture.

Proboscis monkeys are one of the most distinctive looking primates on the planet, having the longest noses of all primates. In Sabah, only 15% of proboscis monkey groups are in fully protected areas. The remaining populations are divided between those residing outside of the reserve network completely or those within partially protected forest reserves, where different levels of extraction are permitted.

The study looked at different scenarios to determine their influence on the declining population trends of three populations, two in Kalimantan and one in Sabah. The Sabah population was the Lower Kinabatangan Wildlife Sanctuary. The conservation strategies evaluated in the study were: (1) eliminating hunting; (2) eliminating fires; (3) eliminating deforestation; (4) reducing deforestation; (5) implementing reforestation programs and (6) reconnecting sub-populations.

The study used current population surveys and predicted a decrease of about 1,000 monkeys within the next 50 years in the Lower Kinabatangan Wildlife Sanctuary. It was found the scenario with the greatest improvement on each population was reconnecting the population through forest corridors in the Lower Kinabatangan Wildlife Sanctuary.

Danica Stark, PhD student, School of Biosciences & lead paper author said: "Recent surveys carried out by the non-governmental organization HUTAN and Danau Girang Field Centre showed a similar pattern of population decrease in the Lower Kinabatangan Wildlife Sanctuary.

"Whilst the Lower Kinabatangan Wildlife Sanctuary population is not predicted to become extinct within the next 50 years (probably because of its current high population size - of about 3,000 individuals), it is extremely likely that if nothing is done to stop deforestation and the increase of habitat loss and fragmentation, and to reconnect forest fragments along the main river and its tributaries, the proboscis monkey population will become in great danger of extinction."

Laurentius Ambu, Director of the Sabah Wildlife Department said: "There has been a strong conservation presence in the Lower Kinabatangan Wildlife Sanctuary in the past decade. However, there are too many narrow strips of forest along the Kinabatangan which are not sufficient and can result in the death of monkeys and their feeding trees due to over-exploitation. We need to identify the severity of riverine forest which have been converted into plantations and restore these forests."

"There are governments and local reforestation initiatives organised and implemented in and around the Kinabatangan region, joining local communities, oil palm schemes, and eco-tourism in halting forest loss and playing an important role in reconnecting the forest. The reforestation projects and protection against further expansion of oil palm plantations will have a positive influence on the proboscis monkey populations, getting stronger and more stable with time. However, we need to act now, increase the reconnection between forest fragments and reestablish large strips of riparian forest along the main river and its tributaries if we want the proboscis monkey to continue striving in Sabah and attract tourists," concluded Laurentius.

Sime Darby Foundation is currently funding a 3-year project on proboscis monkey to Danau Girang Field Centre and Sabah Wildlife Department to carry out research and conservation work towards a better management of the proboscis monkey populations in Sabah. The project aims to produce a management plan for the proboscis monkey in Sabah.