Proboscis monkey / Bangkatan / Monyet Belanda (Nasalis larvatus)
IUCN Red List category & criteria: Endangered A2c ver 3.1
Recent publications:
Endemic to the Island of Borneo, the proboscis monkey (Nasalis larvatus) is an endangered primate species, mostly threatened by the habitat loss and fragmentation. They are found in riverine, mangrove, freshwater and peat swamp forests, areas which tend to be first colonized, farmed, industrialized and least protected by man. Although the movement and dispersal of proboscis monkeys is not restricted by water, populations become isolated due to the increasing loss of habitat by logging and agriculture (palm oil plantations). Proboscis monkeys are selective feeders that follow the leaf-eating pattern among colobines, therefore increasing their vulnerability to habitat loss and degradation.
Proboscis Monkey Conservation Program
Principal Investigator: Benoît Goossens
In 2005, an extensive state wide survey was conducted to establish the population status and to assess the threats to the survival of this species in Sabah (Sha et al. 2008). The population size was estimated to a minimum of 5,907 individuals found along major coastal river systems in Sabah. The distribution of the proboscis monkeys appeared highly fragmented, with only five major centers of continuous distribution (three on the east coast, one on the west coast, and one in the south of the state) and numerous small isolated populations. Moreover, only 15.3% of the population estimated was found within protected forest reserves, with much of the species’ diminishing range habitats exposed to further conversion, extraction and disturbance.
The Proboscis Monkey Conservation Program aims to gain better understanding of the current demographic, genetic and health status of this species populations.
Main objectives:
1) Research and conservation of one of the most charismatic (and endemic) primate species of Borneo, the proboscis monkey.
2) Rescue and translocation operations of pocketed populations of proboscis monkeys in unviable habitats.
3) Promote the restoration and re-establishment of wildlife corridors along large rivers in Sabah that will be emphasized during an international workshop at the end of the project.
4) Increase the capacity in conservation biology and wildlife management within the Sabah Wildlife Department through high-education training of a senior wildlife officer, one SWD/DGFC veterinarian, and one international PhD student.
Samples and data are being collected from proboscis monkeys from all the five major centres throughout Sabah. The project team is capturing and sampling between 5 and 15 individuals per population. The samples include blood, saliva, urine and faeces; ecto-parasites and morphometric data are also being collected. Some of the analyses being made include blood biochemistry, nutrition, population genetics, and parasite and virus identification. In addition, satellite collars were deployed on individuals from different populations, and the forest quality and its level of disturbance is being quantified with the aid of drones (Unmmaned Aerial Vehicles).
In February 2017, an international workshop has been held on the conservation of the proboscis monkey in Borneo to present the results of the work carried out on the species and to discuss these results with all stakeholders involved in the conservation of the proboscis monkey. A Population and Habitat Viability Assessment (PHVA) for the taxon was also carried out before the workshop encompasing population-specific management goals, the results of the PHVA have also been presented at the workshop. Two significant outputs resulting from this workshop will be the production of a Resolution to be tabled before the State Cabinet of Sabah and the production of a final State Action and Management Plan for the proboscis monkeys. We will also stress out the importance of wildlife corridors along the main rivers in the country that will benefit not only for the proboscis monkey but also for other endangered species such as orang-utans, Bornean elephants, eight species of hornbills, etc.
Projects within the Proboscis Monkey Conservation Program
Conservation genetics and management of the proboscis monkey (Nasalis larvatus) in Sabah.
PhD Candidate: Senthilvel KSS Nathan
Institution: Cardiff University
Supervisors: Benoît Goossens, Michael W Bruford, , Pablo Orozco-terWengel
Advisor: Milena Salgado Lynn
Molecular biologist: Cyrlen Jalius
Duration: October 2011- October 2019
The rapid area decrease and fragmentation of N. larvatus habitat is likely to have led to a significant decrease in population sizes, and hence to a significant genetic impoverishment. It is therefore crucial to rapidly sample as many populations as possible to determine the extent of genetic diversity present in remnant populations (continuous and isolated) and to characterise their genetic health in order to propose management measures to restore and re-establish healthy populations of proboscis monkeys. Habitat loss and fragmentation have also increased isolation of proboscis monkey groups, therefore rescue and translocation operations in all areas where the monkeys are at high risk of being killed are also needed.
The aim of this study will be to examine the phylogeographic patterns, genetic diversity and differentiation within and between the five major centres of continuous population distribution and the small isolated populations of proboscis monkeys. This data will provide the Sabah Wildlife Department with accurate information about genetic diversity and genetic health of the proboscis monkey in Sabah to include in the conservation management program of the species in the state.
The specific objectives of this study are the following:
- Determine the population structure and demographic history of the proboscis monkey in Sabah.
- Identify the level of genetic differentiation between sub-populations and the threats to genetic diversity.
- Determine if and how are landscape (riverine and mountain barriers) and environmental factors are influencing gene flow and population structure in the proboscis monkey populations in Sabah
- Simulate changes in genetic diversity and differentiation within and among fragmented populations of proboscis monkeys in Sabah using different management scenarios and examine the genetic implications of management options for fragmented populations of proboscis monkeys (following Bruford et al. 2010).
- Subsequently, identify appropriate intervention measures to maintain gene flow and diversity between the proboscis monkey sub-populations in Sabah.
Fragment size, edge effects, and anthropogenic factors influences on the movement, distribution of proboscis monkeys (Nasalis larvatus) in the Kinabatangan Floodplain, Sabah.
PhD Candidate: Danica Stark
Institution: Cardiff University
Supervisors: Benoît Goossens, Ian Vaughan
Duration: Completed
Responses to habitat loss and forest fragmentation are species specific and need to be examined as such. Habitat loss and fragmentation are challenging wildlife, and species with large home ranges or that are habitat specialists are particularly vulnerable to this. Although there have been many studies examining primate responses to habitat loss and fragmentation, they have focused mainly on abundance and density. Home ranging and other detailed ecological responses have not played a large role in these discussions, but are crucial given the functional roles primates play in their ecosystems. It is likely that different primate species will respond differently to habitat loss or other anthropogenic activities according to differences in their ecological traits.
Research Questions:
- How large are proboscis monkey home ranges and how is this estimate affected by the method of analysis?
- Is there a simple, low-cost, yet ecologically-meaningful way of collecting data/mapping in remote/difficult areas using drone data to map habitat?
- Do forest characteristics impact the range size, intensity rates or recursion rates? Protected forest vs unprotected forest.
- What is the short-term variation in habitat use for the foraging or movement ecology of proboscis monkeys?
Satellite collars were put on proboscis monkeys, which is the first time ever for this species. As proboscis monkeys tend live in swampy, wet areas, it is often difficult to track them by foot continuously, particularly in the wet season when the forest can flood. Furthermore, due the difficulties in habituating and tracking a primate group, previous studies have only been able to track one group at a time, and are limited by factors such as weather, which can prevent field work. By using GPS collars, ten groups were tracked across different seasons, with multiple groups tracked simultaneously. Drones (Unmanned aerial vehicles) were used to map the home range of the proboscis monkeys in order to produce high resolution and ecologically-meaningful habitat maps.
The results produced from the project are expected to be used in developing a State Action Plan for the management plan of proboscis monkeys in Sabah. It will demonstrate the amount of forest necessary for the survival of the species, in terms of space available, food resources and connectivity to allow for movement between groups/sub-populations.
Health Evaluation and comparative status of free- ranging proboscis monkeys (Nasalis larvatus) on their natural habitat in Borneo, Sabah, Malaysia
MSc Candidate: Diana Ángeles Ramírez Saldívar
Institution: Institute of Tropical Biology and Conservation, Universiti Malaysia Sabah
Supervisors: Charles S. Vairappan, Benoît Goossens
Duration: ongoing
- To carry out corporal evaluation as a health indicator, by recording full body measurements, physiologic parameters and vital signs.
- To determine the concentration of some macro and micro minerals; water soluble and fat soluble vitamins; haematology profile and serum biochemistry.
- To evaluate levels of cortisol in serum, faeces and hair as an indicator of chronic stress.
Eco-ethology of proboscis monkey, Nasalis larvatus, and assessment of its role in forest regeneration along the Kinabatangan River
PhD Candidate: Valentine Thiry
Institution: Université Libre de Bruxelles
Supervisors: Martine Vercauteren, Roseline C. Benudel-Jamar, Benoît Goossens
Duration: October 2014 – October 2018
Valentine is studying proboscis monkeys, and their feeding ecology in particular. She makes her behavioural and ecological observations along the Kinabatangan riverside, and collects faecal samples every morning at sleeping sites. She will study proboscis monkey’s diet using the DNA metabarcoding methodology by comparing short chloroplast DNA sequences found in faeces to a plant DNA Database (a database she builds along the way for this purpose). Her aim is to identify proboscis monkey’s food items in the Kinabatangan fragmented landscape and to study the seasonal dietary variations throughout the year. Interested in the role proboscis monkeys could potentially play in seed dispersal, she will also investigate faecal samples for their content in seeds and set up different germination tests. Finally, she will study how the phytochemical composition of leaves varies between consumed and not-consumed plant species, with a gradient distance to the river.
The project aims to determine which the key plant species for N. larvatus are in the fragmented landscape of the Lower Kinabatangan Wildlife Sanctuary and to contribute to the conservation of this endangered species.