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Distribution and conservation of the proboscis monkey (Nasalis larvatus) in Kalimantan, Indonesia
Abstract
The proboscis monkey Nasalis larvatus is endemic to the island of Borneo. A review of the species' distribution reveals that it occurs throughout Kalimantan, the Indonesian part of Borneo, from the coastal areas to the headwaters of probably all major rivers. Proboscis monkeys are more widely distributed than has been thought previously, and were never confined to the coastal and downstream areas of rivers on the island of Borneo (including what is now Sabah, Sarawak, Brunei and Kalimantan) as has been assumed in some primate literature. Proboscis monkey habitat, i.e. riverine and coastal forest, is the most threatened of all vegetation types in Borneo, owing to conversion into agricultural land and logging. Another threat to their survival is hunting. The combination of these threats has reduced populations of N. larvatus in Sabah, Sarawak and East Kalimantan, and based on this it is expected that other populations elsewhere in Borneo are likewise threatened. Our study shows the present low efficiency of conservation programmes in Kalimantan, which adds to the problem of protecting N. larvatus. For the survival of the species the populations in Kalimantan are still of great significance, as they are considerably larger than those in Sabah, Sarawak, and Brunei. We therefore recommend the protection of some of the largest populations in order to ensure the long-term survival of the species.
... Proboscis monkeys face a multitude of threats, first and foremost is loss of habitat, either through conversion of natural forest to plantation forest, clear-felling of forest, including mangroves, for its timber or for conversion into to agricultural land, or by poor management of existing forests [10,40,69]. Infrastructural development, including the creation of a new capital, Nusantara, in East Kalimantan, and roads throughout Borneo [5,10,42], ads further pressure on already imperilled populations of the species. ...
... Infrastructural development, including the creation of a new capital, Nusantara, in East Kalimantan, and roads throughout Borneo [5,10,42], ads further pressure on already imperilled populations of the species. Habitat loss, habitat fragmentation and infrastructural development allow humans to get into more, and closer, contact with proboscis monkeys leading to conflict which ultimately may result in the capturing and/or killing of the monkeys [33,40,69]. In Indonesia, only a small proportion of the species' potential habitat, around 9%, is included in the country's protected areas network [85]. ...
... A quarter of a century ago Meijaard and Nijman [40] concluded that the trade in proboscis monkeys did not constitute a significant threat to the species. Habitat conversion, fires and hunting was seen as posing a much larger threat to their survival. ...
Proboscis monkeys Nasalis larvatus are endemic to the island of Borneo (politically shared between Malaysia, Brunei Darussalam and Indonesia) and are threatened by habitat destruction, fires and hunting. Because of their specialised diet, they are very challenging to maintain in captivity and in the past live trade was not seen as an impediment to their conservation. We report on and review the trade in proboscis monkeys over the period 1999–2024, based on published literature, media reports, seizure records, court rulings and communication with experts. We found no records for Malaysian Borneo or Brunei. We found 25 reports in the Indonesian media (concerning 52 proboscis monkeys), mostly from after 2016, and mostly from the province of South Kalimantan (14 reports) but also from the islands of Sulawesi and Java, both gateways for export and neither within the natural range of the species. In 2024 one proboscis monkey was seized in Mumbai, India, coming from Indonesia. Proboscis monkey skulls were found in trade in wildlife shops in Bali in 2022–2025, specifically targeting foreign tourists. Online traders in Sumatra, Kalimantan and Java were found offering at least 48 proboscis monkeys for sale. Between 2016 and 2024, 14 people were prosecuted in Indonesia for trading, transporting or keeping a total of 42 proboscis monkeys, receiving a mean fine of USD1,795 (out of a possible maximum of USD6,150) and a mean sentence of 13 months in prison (out of a maximum of 5 years). Prior to the turn of the century there were very few proboscis monkeys in zoos, but in recent years this has changed, and now there are at least 74 individuals in 10 Indonesian zoos and 2 individuals in a Malaysian zoo, in addition to at least 31 individuals in zoos in Singapore, China and Japan. Our review shows that not only are zoos increasingly acquiring this species but that proboscis monkeys are also increasingly available in the illegal wildlife trade. We urge the authorities, especially in Indonesia, to increase the efforts to enforce existing legislation and to be more active in their efforts to curb the trade in these globally threatened primates.
... One of the affected species is the proboscis monkey (Nasalis larvatus), endemic to the island of Borneo, and classified as endangered with a declining trend by IUCN (Boonratana et al., 2020). Proboscis monkeys are threatened locally by hunting and throughout the range by habitat loss (Meijaard & Nijman, 2000;Sha et al., 2008). They mainly occur either in one-male-multi-female breeding units (OMU) or all-male units (AMU) and inhabit mangroves and riparian forests, which are probably the fastest disappearing forest types in Borneo (Langner et al., 2007). ...
... The current total population of the proboscis monkey remains unknown. The rough estimate of 25,000 (Manansang et al., 2005) was based on published estimates from major political divisions of Borneo that are now 15-35 years old (Bennett & Sebastian, 1988;Meijaard & Nijman, 2000;Salter & MacKenzie, 1985;Sha et al., 2008). Recent studies updated data for some populations in Sabah, namely those in the Klias Peninsula (679 individuals; Bernard et al., 2021), Lower Kinabatangan (1960Matsuda et al., 2020), and for Balikpapan Bay in East Kalimantan. ...
... Recent studies updated data for some populations in Sabah, namely those in the Klias Peninsula (679 individuals; Bernard et al., 2021), Lower Kinabatangan (1960Matsuda et al., 2020), and for Balikpapan Bay in East Kalimantan. The Balikpapan Bay population was originally described to contain between 100 and 1000 individuals (Meijaard & Nijman, 2000) or 1400 individuals (Stark et al., 2012). Toulec et al. (2022) increased the estimate to at least 1800 individuals. ...
Populations of rare and endangered species are nowadays in peril due to large-scale habitat conversion, and even sizeable and stable populations are confronted with unexpected challenges. We conducted a full census of a proboscis monkey (Nasalis larvatus) population in Balikpapan Bay and located 292 one-male-multifemale units and 67 all-male units in 2022. Using data on average group size, subsampled from Balikpapan Bay, we estimated a total population size of 3907 individuals. The rate of proboscis monkey habitat loss in Balikpapan Bay has been slowing down to the current 0.69% per year. It is predicted that habitat recovery may exceed habitat loss after 13 years. The Indonesian capital city relocation was announced in 2019 with spatial plans designed to cover a total land area of 2,560 km² across various habitats until 2045. A total number of 1449 individuals (37.08% of the population) were found on 80.55 km² (41.29%) of habitat that overlapped with current spatial plans of Nusantara Capital city. The construction work just started; before that, the government had already claimed it would be a “smart, green, beautiful, and sustainable city”. We, therefore, include our recommendations to mitigate the impact of the construction and to pursue the goal to construct the most sustainable capital city, concerning local biodiversity and thus become a pioneer in a new direction of proboscis monkey conservation.
... Nasalis larvatus, commonly known as the Proboscis monkey, is an endemic primate of the island of Borneo. They can be found in riverine forests, peat swamps, mangroves as well as mixed dipterocarp forests (Bennett and Sebastian, 1988;Meijaard and Nijman, 2000;Kombi and Abdullah, 2013;Chong et al., 2018;Laman and Aziz, 2019;Mazlan et al., 2019). Taxonomically, the Proboscis monkey is categorised under the family Cercopithecidae and subfamily Colobinae. ...
... The Proboscis monkey is now listed as 'Endangered' by the IUCN Red List and under Appendix I of CITES. Habitat destruction and poaching have been the major causes of its population decline (Meijaard and Nijman, 2000). They are also hunted for the bezoar stones in their intestines, which are highly valued by traditional Chinese medicine practitioners (Sha et al., 2011). ...
... In Sarawak, (Meijaard et al., 2008). A combination of hunting, degradation of habitat from logging activities, and conversion to agricultural land were identified to significantly impact the Proboscis monkey population (Meijaard and Nijman, 2000). ...
Nasalis larvatus, commonly known as the Proboscis monkey, is an endemic primate of the island of Borneo. They can be found in riverine forests, peat swamps, mangroves as well as mixed dipterocarp forests (Bennett and Sebastian, 1988; Meijaard and Nijman, 2000; Kombi and Abdullah, 2013; Chong et al., 2018; Laman and Aziz, 2019; Mazlan et al., 2019). Taxonomically, the Proboscis monkey is categorised under the family Cercopithecidae and subfamily Colobinae. Being a Colobine monkey, leaves constitute its dietary mainstay. Nevertheless, it also eats fruits, seeds, and shoots from mangrove plants (Yeager, 1989). Unlike other Colobine species, the Proboscis monkey possesses compartmentalised stomachs, and stomach bacteria help to ferment the food.
The Proboscis monkey is now listed as ‘Endangered’ by the IUCN Red List and under Appendix I of CITES. Habitat destruction and poaching have been the major causes of its population decline (Meijaard and Nijman, 2000). They are also hunted for the bezoar stones in their intestines, which are highly valued by traditional Chinese medicine practitioners (Sha et al., 2011). A severe decline in population numbers will result in the loss of some genetic information unique to the species.
The Proboscis monkey population in Sarawak was estimated at under 2,000 individuals by Salter and MacKenzie (1985). A survey by Bennett et al. (1987) estimated that the Proboscis monkey population in Sarawak was less than 1,000 individuals. Nonetheless, the species is widely distributed, with considerable fragmented populations primarily concentrated in the western part of Sarawak (Salter and MacKenzie, 1985). In Sarawak, the Proboscis monkey is listed as ‘Totally Protected’ under the Wild Life Protection Ordinance, 1998. Consequently, this species cannot be kept as a pet, hunted, captured, killed, sold, imported or exported, nor owned (including any recognisable parts) without written permission from the Controller of Wild Life. The penalty for such an offence is a fine of RM30,000 and two years’ imprisonment. However, in the year 2000, the IUCN status of the primate changed from ‘Vulnerable’ to ‘Endangered’ (Meijaard et al., 2008). A combination of hunting, degradation of habitat from logging activities, and conversion to agricultural land were identified to significantly impact the Proboscis monkey population (Meijaard and Nijman, 2000).
The Proboscis monkey population has reportedly decreased by over 50% over the last 40
years (Meijaard et al., 2008). Therefore, immediate action is urgently needed to conserve
this primate in Sarawak. An action plan for conserving the Proboscis monkey in Sarawak
has been proposed for 2021 to 2025, based on population size, distribution, genetic
diversity, and health data.
Objectives
The specific objective of the current project is to formulate a long-term action plan
which will provide the Sarawak Forestry Corporation with detailed guidelines on
the conservation and management of the endangered Proboscis monkey (Nasalis
larvatus) in Sarawak from the year 2021 to 2025.
Action plan scope
I. Review of the conservation status of the Proboscis monkey in Sarawak
II. Review of the population estimates, genetic variations and parasite infections in the Proboscis monkey from Sarawak
III. Recommendations for the implementation of a five-year action plan (2021 to 2025) for surveying and monitoring the Proboscis monkey in Sarawak
IV. Recommendations for research and eco-tourism activities related to the Proboscis monkey in Sarawak
... Endemic to the island of Borneo, proboscis monkeys Nasalis larvatus primarily live in seasonally flooded lowland habitats, such as mangrove and riparian forests (Kawabe & Mano, 1972;Meijaard & Nijman, 2000a;, where they occur at very different densities both within and between habitat types (riparian 25.5-62.6 individuals/km 2 ; mixed forest types 4.4-6.9 ...
... These loose congregations usually split in the morning into individual groups to forage some distance from the riverbanks. The major threats to proboscis monkeys include loss of mangrove and riparian forest (mainly due to conversion into aquaculture, agriculture, or destruction due to forest fires), habitat fragmentation, and also hunting locally (Boonratana, 2013;Meijaard & Nijman, 2000a;Sha et al., 2008), yet the impact on individual populations remains largely undocumented. ...
... Population size estimates for the four major political divisions of Borneo (i.e., the Malaysian states of Sabah and Sarawak, Indonesian Kalimantan, and Brunei Darussalam) differ widely, and many are based on surveys and extrapolations from over a decade ago: Sabah (5907: Sha et al., 2008), Sarawak (fewer than 1000 individuals: Bennett, 1988;9586: Laman & Aziz, 2019), Brunei (420: , Kalimantan (∼8000-12,000: Meijaard & Nijman, 2000a;9200: Manansang et al., 2004). The accuracy of those estimates could be biased. ...
Systematic and well-structured monitoring is essential for taxa with high extinction risk such as primates. Endangered proboscis monkeys Nasalis larvatus are endemic to Borneo, where they are found scattered across lowland habitats of the island, which are under strong anthropogenic pressure. A large population of proboscis monkeys in Balikpapan Bay, Indonesian Borneo, was predicted to decline due to the ongoing habitat loss and degradation, notably because of forest fires. We examined changes in the number and composition of groups of a part of this population from 2007 to 2017, which included a period of forest fires linked to the El Niño-Southern Oscillation events. We conducted a census from a boat; attempting to locate all proboscis monkey groups within the Balikpapan City administrative area in 2007, 2012, and 2017. During the most recent census, we observed a total number of 60 proboscis monkey groups in two subpopulations. The population density was 1.14 group per km2 of suitable habitat. Contrary to previously published predictions, we did not find evidence of a population decline. Contrary to predictions, the 2015 El Niño induced fires impacted mainly forests on ridges and slopes, thus affecting only a small part of the proboscis monkey habitat located close to rivers and mangrove swamps. However, the increasing population density of monkeys, coupled with ongoing habitat degradation and habitat loss in one of the subpopulations, suggests that proboscis monkey population in Balikpapan Bay may be approaching a limit of resilience to habitat changes. In case it proves infeasible to census all individuals in the whole population, we recommend using a group-level census, connected with systematic group counts to obtain a reasonably precise proboscis monkey population size estimate.
... It also contributes to the decreasing of the habitat suitability for proboscis monkeys [3,9]. In long term, it increases the level of vulnerability to local [7,10]. On the contrary, some studies reported that fragmented habitats can still support proboscis monkey population, such as in the Sungai Hitam, Samboja [11]. ...
... We assumed that the level of human disturbance caused this phenomenon. This behavior is understandable because of its tendency to be timid and avoid humans [10,16]. The river estuary area has more settlements. ...
... But, we considered the process to be at a low level because we found only 3 infants during the observation. On the other hand, the infant itself is an age group that is prone to death due to predators or other natural causes [10,16]. Although, low number of juveniles and infants is not an indicator of a decline in natality. ...
A population estimation of proboscis monkeys ( Nasalis larvatus ) has been conducted in Manggar River, Balikpapan. In this non-conservation area, the anthropogenic activities threaten the proboscis monkey habitat. Boat survey technique was applied along ± 17 km of the river in the morning and evening. The number of proboscis monkeys in the surveyed area was estimated to range from 57 to 69 individuals with estimated population density of 4.75 individuals/Km ² . Moreover, the population of this primates was divided into 4 groups and the sex ratio between adult males and females was 1:2.33. The proboscis monkeys were distributed in the middle of the river to the upstream. The highest population was found in the upstream area with less human activities. Conservation efforts in the Manggar River need to be carried out considering the proboscis monkey habitat in the area has been fragmented and isolated. These efforts could involve local economic communities.
... Pada tahun 2000, laju deforestasi habitat bekantan tercatat sebesar 3,49% per tahun. Sebelumnya, pada tahun 1995 telah terjadi penurunan luas 6 tipe ekosistem habitat antara 20-88% (Meijaard & Nijman, 2000) dan laju penurunan ke enam habitat ini, baik di dalam maupun di luar kawasan, adalah sebesar 2% per tahun (Manansang dkk., 2005). Akibatnya, populasi bekantan cenderung menurun karena primata ini kurang toleran terhadap kerusakan habitat. ...
... Sebaran populasi bekantan telah terpencar antara 15-40 km (Bismark & Iskandar, 2002), sedangkan populasi bekantan yang tersisa di habitat terfragmentasi berupa ladang dan permukiman telah dianggap sebagai hama oleh sebagian masyarakat (Soendjoto dkk., 2005). Pada tahun 1990 habitat bekantan telah dilaporkan berkurang seluas 49% dan pada tahun 1995 dilaporkan tinggal 39% dan hanya 15% dari habitatnya berada di kawasan konservasi (Meijaard & Nijman, 2000). Perkiraan penurunan habitat bekantan sekitar 2% setahun akibat kerusakan habitat tidak hanya terjadi di luar kawasan konservasi, bahkan telah memasuki kawasan konservasi. ...
Indonesia adalah negara negara megabiodisersity. Meskipun luas wilayah nya hanya 1,3% dari luas muka bumi, namun Indonesia memiliki 12% ma malia, 16% reptilia, 10% tumbuhan, 25% ikan dan 17% burung yang ada di dunia. Pemerintah telah melakukan berbagai upaya perlindungan, penga wetan dan pelestarian keanekaragaman hayati, antara lain melalui pen cadangan kawasan hutan sebagai hutan konservasi seperti taman nasio nal, cagar alam, suaka margasatwa, taman wisata alam, taman hutan raya, dan taman buru. Disamping itu, pemerintah juga menetapkan jenis-jenis tumbuhan dan satwa yang dilindungi melalui Peraturan Menteri Lingkungan Hidup dan Kehutanan Nomor P.106/MenLHK/Setjen/KUM.1/12/ 2018. Upaya konservasi satwa juga dilakukan melalui penyusunan Strategi dan Rencana Aksi Konservasi spesies yang terancam punah serta penetapan 25 spesies prioritas. Peningkatan populasi 25 spesies prioritas sebesar 10% dari baseline data 2013 merupakan salah satu yang akan dicapai pemerintah. Upaya pening katan populasi tersebut antara lain dilakukan melalui pembinaan populasi, penanggulangan konflik, perlindungan dan pengamanan, penyadartahuan, rehabilitasi dan pelepasliaran, pengelolaan dan pengem- bangan pangkalan data. Buku bunga rampai berjudul “Mengenal Lebih Dekat Satwa Langka Indonesia dan Memahami Pelestariannya” adalah karya para peneliti konservasi keanekaragaman hayati lingkup Kementerian Lingkungan Hidup dan Kehutanan yang dirancang untuk konsumsi publik dengan tujuan mengenalkan kekayaan keanekaragaman hayati satwa dan mensosialisasikan upaya-upaya konservasinya. Harapannya adalah masyarakat ber tambah pengetahuannya, meningkat pemahamannya dan akhirnya ber partisipasi serta mendukung segala upaya konservasi keanekaragaman hayati pada umumnya dan satwa langka yang terancam punah pada khususnya. Buku mencakup berbagai jenis satwa liar yang ada di Indonesia dari Pulau Sumatera hingga Papua
... These monkeys are known to be the largest representatives of colobines and they are the only members of the genus Nasalis [Napier & Napier 1967;Medway 1977]. They are largely restricted to coastal lowland mangrove, riparian, and swamp forests [Kawabe & Mano 1972;Wolfheim 1983;Salter et al. 1985, Boonratana 1993Bernard 1997] up to 750 km inland, but usually less than 55 km from the coast, and at altitudes below 350 m above sea level [Medway 1977;Salter & Mackenzie 1985;Bennett & Sebastian 1988;Meijaard & Nijman 2000]. Proboscis monkeys are closely associated with water-ways, traveling inland to forage (generally up to 1 km) and returning to their sleeping sites along the river edge every evening [Bennett & Sebastian 1988;Yeager 1989;Boonratana 2000]. ...
... In Sabah, the species is listed as totally protected. Hunting, degradation of their habitats by logging and conversion into agricultural land (particularly for palm oil production), were identified as the major factors in the decline of their population [Meijaard & Nijman 2000]. ...
Proboscis monkeys, Nasalis larvatus (Wurmb, 1787), are indigenous to the island of Borneo and are considered one of its most emblematic species. Today the conservation status of this primate is classified as Endangered on the IUCN Red List and listed under Appendix I of CITES, prohibiting all international commercial
trade. In the Malaysian state of Sabah, the species is listed as totally protected and cannot be hunted. Continuing studies suggest that the number of proboscis monkeys has been decreasing in recent years. These studies have identified various
factors contributing to this decline and its potential consequences. In order to carry out a thorough assessment of the conservation status of the species it is essential to have a good understanding of the animal’s ecology and habitat requirements and to use research-based approaches. One of such are species distribution models (SDMs), which in recent decades have become widely used tools in ecology by relating species occurrences to environmental data to gain ecological insights. In this work, we specifically evaluated the effect of environmental parameters such as cloud cover to predict the potential distribution of the proboscis monkey in Sabah. Cloud cover, a seemingly simple atmospheric phenomenon, exerts a profound influence on a wide range of ecological biological processes, yet the assessment of its
importance has remained remarkably limited. For modelling purposes the ‘flexsdm’ R (v. 3.3.3) modelling package was employed for testing out the Maximum entropy (Maxent) algorithm, one of the most widely used SDM modelling methods. Model evaluation gave satisfactory results and the resulting model found
a high level of suitability for proboscis monkeys in nearshore areas. A concerning discovery is that perhaps less than 13% of Sabah’s area is suitable habitat for proboscis monkeys, raising questions about their long-term viability. Cloud cover, particularly average annual cloudiness, is a key environmental factor influencing
the distribution of proboscis monkeys in Sabah. The conversion of Borneo’s forests to oil palm plantations can negatively impact cloud properties, potentially threatening the monkeys’ habitat.
... Understanding the gut microbiome is essential for unravelling the mutualistic relationship between organisms and gut microbes, especially in light of rapid and extensive habitat changes. This knowledge aids in explaining the adaptation process within changing environments, particularly for endangered species like the proboscis monkey (Nasalis larvatus) where habitat loss, degradation, and fragmentation pose signi cant threats to their survival [11][12][13][14]. ...
... The species has been red-listed by the IUCN as an Endangered species since 2000 [14][15]. They are known to inhabit primarily lowland wetland forests along rivers and coastal areas such as riverine, mangrove, peat swamp and freshwater swamp forests [13][14][15]. They are folivores, feeding on a variety of plant parts including young leaves or shoots, unripe fruits, including seeds, and owers [11,14,16,17]. ...
Numerous research on the gut microbial diversity of non-human primates (NHP) has been done to evaluate the impact of environmental changes on the diversity of gut microbiota and to determine the mutualistic relationship between the animals and gut microbes that aid in their adaptation to living in an altered environment. The metagenomics approach was employed to explore gut microbial diversity and abundance in the endangered and endemic proboscis monkeys of Borneo. The amplicon sequencing of the 16S ribosomal RNA (rRNA) gene from 24 faecal samples successfully generated over two million raw reads of bacteria (98%) and archaea (2%) representing 4030 OTUs. Gut microbial diversity and abundance vary across different populations, i.e.: wild, semi-wild and captivity, suggesting that higher diversity was discovered in individuals inhabiting areas with higher food resource availability in natural habitats. The observed alterations in gut microbial diversity and abundance among proboscis monkey populations inhabiting distinct environmental conditions in this study provide empirical evidence for the impact of environmental changes on the proboscis monkey’s gut microbiota. Besides, the prevalence of pathogenic bacteria identified in the proboscis monkey’s gut highlights the potential hazards associated with human-primate interactions and raises the urgent need for public health management. [197 words]
... River access often causes riparian forests to rapidly change into other land uses, such as settlements, cultivation, oil palm plantation [1], tourism facilities [2], coal loading areas and hauling routes [3]. The habitat of proboscis monkey has decreased by more than 45% from its initial habitat of 121,670 km 2 [4], with an estimated damage rate of 2% per year [5], and only 9% of this number is currently still in protected areas [6]. This IOP Publishing doi: 10.1088/1755-1315/1282/1/012018 2 reduction and decrease in habitat quality is followed by a decline in the proboscis monkey population, predicted to be around 70% in the last 36 years [7]. ...
... The estimated proboscis monkey population based on monitoring data conducted by the East Kalimantan BKSDA in 2022 at the Muara Kaman Sedulang Nature Reserve ranged from 364-644 individuals. This estimate is categorized as low because it is less than one thousand individuals [4]. This low proboscis monkey population may indicate that riparian conditions in the reserve have been damaged. ...
Proboscis monkey ( Nasalis larvatus Wurmb.) is an endemic primate species to Borneo’s island. Muara Kaman Sedulang Nature Reserve is one of protected area for this species in the island, but it’s riverine habitat is largely lost by forest fires and conversion for aquaculture, agriculture and settlements. A conservation action in the area needs spatial information regarding the habitat suitability of proboscis monkey. This study aimed to project a spatial model for habitat suitability of proboscis monkey in the reserve through species distribution modelling (SDM) using the Maximum Entropy (MaxEnt), based on the species’ occurrence records and environmental predictors. The results showed that suitable habitat for proboscis monkey was 3,410.27 ha (5.22% of the nature reserve total area). Model performance evaluation shows an accuracy of the Area Under Curve (AUC) value of 0.940, which is a very good category. Jackknife-test results showed the presence of secondary swamp forest (40.8%), distance from water bodies (25.9%), land cover (12.4%), secondary forest (6.3%) and mixed gardens (5.1%) are five variables that significantly contribute to the distribution of proboscis monkeys in the reserve. This study provides suggestions for conservation of proboscis monkey in remaining suitable habitat, which include local people involvement, monitoring and habitat restoration.
... In 2000, the conservation status of Proboscis Monkey was elevated from 'Vulnerable' to 'Endangered' under the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, as its population faced a severe decline of 50% during the past 40 years (Meijaard et al. 2021). Significant threats to Proboscis Monkey's population include hunting, illegal logging and land conversion (Meijaard and Nijman, 2000). ...
... This distance of 0.75 km was applied as a conservative estimate to standardise the ranging distance used by the Proboscis Monkey in Limbang Mangrove National Park. This distance is within the range of the species' reported daily movement (less than 1 km from the riverbank) (Medway 1977;Bennett and Sebastian 1988;Yeager 1991;Boonratana 2000;Meijaard and Nijman 2000;Matsuda 2008;Bismark 2010). ...
The Proboscis Monkey is endemic to Borneo, where the species is widely
distributed in mangroves and estuarine habitat. Sensitive to disturbance, and with a
declining population listed by IUCN as ‘Endangered’, protective legislation is generally in
place. Treated as an ‘iconic’ species for tourism in Sarawak, several mangrove areas have
been protected for conservation of the species. Limbang Mangrove National Park is one
such place but, with an estimated population of 44 individuals in 2019, had become a
critical site. A new survey of 11 boat trips covering 223.59 km of mangrove riverbank in
Limbang Mangrove National Park and adjoining estuaries recorded 236 individuals in 34
groups. The estimated population density was 1.03-1.78 individuals/km2, and 0.15-0.25
groups/km2. Proboscis Monkeys were evenly distributed within the National Park
boundaries, but concentrated at the centre of the Park. A questionnaire survey of local
communities found that more than 50% of respondents supported conservation of this
species. Based on the Boosted Regression Tree analysis, locality and income of the
respondents were the most influential factors that influenced their perception towards the
conservation of Proboscis Monkey in Limbang Mangrove National Park. We conclude that
conservation and sustainable ecotourism activities regarding Proboscis Monkeys in
Limbang Mangrove National Park should give priority to carfeful planning, taking into
consideration the long-term existence of this totally protected species.
... This value indicates that the model is very effective in measuring the presence and absence of N. larvatus (Fielding and Bell 1997;Manel et al. 2001). The high value of AUC on the model can be explained by the fact that AUC value is higher for species with small range size (Phillips et al. 2006;Elith et al. 2011) like the N. larvatus (Meijaard and Nijman 2000). The five of most important variables in a fit model for N. larvatus are altitude, distance to the fish ponds, annual precipitation, land cover and distance to the agriculture. ...
... It is strongly suggested that the other provincial governments follow South Kalimantan government's step in conducting such research in order to give more efforts on the conservation of the monkeys. As reported in Pulau Kaget, the N. larvatus is already extinct due to an insufficient amount of carrying capacity versus the population number (Meijaard and Nijman 2000). The main reason for this extinction lies in the 90% usage of Pulau Kaget as an agricultural area. ...
... Secara umum bekantan tersebar pada habitat lahan basah seperti daerah hutan mangrove, hutan riparian dan hutan rawa, baik rawa air tawar maupun rawa gambut (Salter, Mackenzie, Nightingale, Aken, & Chai, 1985;Boonratana, 1993;Meijaard & Nijman, 2000). Namun demikian, ternyata populasi bekantan juga tersebar di kawasan hutan lainnya. ...
Penelitian populasi bekantan dilakukan di kawasan ekosistem riparian Rawa Gelam, Kabupaten Tapin, Kalimantan Selatan pada bulan Februari-Maret 2014. Tujuan penelitian ini adalah untuk mengetahui kondisi populasi dan struktur kelompok bekantan yang hidup di luar kawasan hutan. Kawasan ekosistem Rawa Gelam merupakan lahan budidaya yang terletak di kanan-kiri Sungai Puting. Vegetasi Rawa Gelam yang tersisa hanya selebar maksimal 200 meter dan di belakangnya terdapat persawahan dan kebun kelapa sawit. Penghitungan populasi bekantan dilakukan dengan metode Total Count Sampling. Berdasarkan hasil penelitian, diketahui populasi bekantan di Rawa Gelam sebanyak sembilan kelompok bekantan, dengan jumlah 192 individu. Kepadatan populasi bekantan di kawasan ekosistem Rawa Gelam adalah 28,34 individu/km2 dengan kepadatan kelompok 1,34 kelompok/km2. Selain bekantan, kawasan Rawa Gelam juga dihuni oleh dua jenis primata lainnya, yaitu Monyet Ekor Panjang (Macaca fascicularis) dan Lutung Hitam (Trachyphitecus auratus). Tercatat ada lima kelompok Lutung Hitam dengan jumlah 47 individu dan tujuh kelompok monyet ekor panjang dengan jumlah 76 individu. Ancaman utama konservasi bekantan di Rawa Gelam adalah perusakan habitat dan perubahan fungsi kawasan. Untuk menyelamatkan bekantan dari kepunahan lokal, perlu dilakukan restorasi habitat dengan menerapkan pola agroforestridan pengembangan ekowisata terpadu.
... These primates are protected from hunting and confinement in Borneo. However, the deforestation of mangrove trees and both human and non-human predators have limited the population (Meijaard & Nijman, 2000a). This study will help in deciphering the phylogenetic order of the retroviruses of primates and identify the retroviruses that are highly conserved in Nasalis larvatus. ...
Nasalis larvatus, also known locally as Proboscis Monkey (Monyet Belanda / Bayau), are endemic to the island of Borneo. These Old World Monkeys which parted from the human lineage 25 MYA are iconic to Sabah and serve as one of the major tourist attraction in Sabah. This current study focused on characterizing the genes linked to immunity and host defense which are the retroviral elements present in the Nasalis larvatus genome. Retroviruses are single stranded RNA viruses that reverse transcribed their RNA into DNA for integration into the host's genome and have been posited to contribute to evolutionary processes. The aim of this study was to assess the genes related to immunity of different types and identification of retroviral elements in the Nasalis larvatus and gather novel data that can benefit in clinical studies and eventually enable effective conservation measures to be taken to protect the Nasalis larvatus in its natural habitats. Polymerase chain reaction (PCR) primers were designed from a total of 7 Retroviruses of non-human primate genes obtained from EST. The primers were used to independently amplify and sequence each DNA segment. The primers were designed using the online primer design tool (Primer 3). Amplification reactions were performed in a 96-well microtiter-plate thermal cycler, following which the PCR products were resolved using gel electrophoresis, extracted from the gel, purified, cloned and sequenced. The resulting sequences were analyzed. Alignment was done using ClustalW following which the phylogeny of the genes was resolved using MEGA5. This study highlighted the relatedness of the immunity related genes among the Nasalis larvatus and other non-primates and presumed ancestors and the descendants by analysis of homologous characters.
... The conservation of proboscis monkeys (Nasalis larvatus), an endemic primate species to the island of Borneo, has become a critical issue due to their declining population and the degradation of their natural habitat. As an arboreal species, proboscis monkeys inhabit various wetland habitats such as gelam swamp ecosystems, peat swamps, and mangrove forests along riverbanks [1], [2]. These ecosystems provide essential resources and conditions necessary for the survival of proboscis monkeys and other wildlife. ...
The conservation of proboscis monkeys (Nasalis larvatus), an endemic primate species of Borneo, faces significant threats due to habitat degradation and declining populations. This study aims to develop a real-time and spatial data analysis-based monitoring system to improve the management of conservation areas for the species’ natural habitats. Conducted in the wetland ecosystems of Curiak Island, South Kalimantan, the research integrates remote sensing, Geographic Information Systems (GIS), and Internet of Things (IoT) technologies to monitor key environmental parameters such as vegetation health, land surface temperature (LST), and others. Indices like the Normalized Difference Vegetation Index (NDVI), Vegetation Health Index (VHI), Vegetation Condition Index (VCI), Temperature Condition Index (TCI), and Environmental Critical Index (ECI) are utilized to assess habitat conditions. Initial results showed poor vegetation health, with an NDVI of 0.6085, high LST of 20.41°C, and considerable environmental stress, reflected by an ECI of 74. Restoration efforts, however, improved conditions, with the NDVI rising to 0.7288, LST decreasing to 20.75°C, and the ECI lowering to 53 in the restoration area, signaling recovery. Though the ECI still suggests moderate environmental stress, the trend is positive. IoT sensors provided continuous real-time data, including CO levels at 0.2 PPM, CO2 at 34,045 PPM, O2 at 20.4% Vol, temperatures ranging from 33.155°C to 33.185°C, humidity between 67.45% and 67.65%, and pH at 6.8. Data on dissolved oxygen, total dissolved solids (TDS), and turbidity were also collected, providing dynamic insights into environmental conditions. The integration of community-based approaches ensures sustainable conservation efforts through local participation. This comprehensive monitoring system supports both proboscis monkey conservation and broader ecological objectives like biodiversity preservation, climate change mitigation, and ecosystem service provision, emphasizing adaptive management in conservation strategies.
... Proboscis monkeys inhabit various riparian and coastal forest environments, including riverine, mangrove and peat swamp forests [28], and their dietary patterns have been reported to be flexibly adapted to these environments; diverse diets in riverine forests with higher plant diversity, and low dietary diversity in mangrove forests where plant diversity is extremely low [29][30][31]. Owing to its adaptable feeding habits, the proboscis monkey is an ideal study species for determining how habitat-specific dietary differences influence gut microbiota. ...
Recent technological advances have enabled comprehensive analyses of the previously uncharacterized microbial community in the gastrointestinal tracts of numerous animal species; however, the gut microbiota of several species, such as the endangered proboscis monkey (Nasalis larvatus) examined in this study, remains poorly understood. Our study sought to establish the first comprehensive data on the gut microbiota of free-ranging foregut-fermenting proboscis monkeys and to determine how their microbiota are affected locally by environmental factors, i.e. geographical distance, and social factors, i.e. the number of adult females within harem groups and the number of adults and subadults within non-harem groups, in a riverine forest in Sabah, Malaysian Borneo. Using 16S rRNA gene sequencing of 264 faecal samples collected from free-ranging proboscis monkeys, we demonstrated the trend that their microbial community composition is not particularly distinctive compared with other foregut- and hindgut-fermenting primates. The microbial alpha diversity was higher in larger groups and individuals inhabiting diverse vegetation (i.e. presumed to have a diverse diet). For microbial beta diversity, some measures were significant, showing higher values with larger geographical distances between samples. These results suggest that social factors such as increased inter-individual interactions, which can occur with larger groups, as well as physical distances between individuals or differences in dietary patterns, may affect the gut microbial communities.
... In total, 626 sample points obtained from the GBIF and the Meijaard study were used, which were proportionally divided into two groups: 70 % (440 points) as training points and 30 % (186 points) as validation points. The data on the Proboscis monkey's presence points were used as samples in this study and were obtained from the Global Biodiversity Information Facility (GBIF, 2022) and were augmented with data from Meijaard and Nijman (2000) study ( Fig. 1). Additionally, data points from both the GBIF and the Meijaard study were adjusted based on the current land cover types using ESA Land Use Land Cover (LULC) 2022 (ESA, 2022), with a focus on forest cover type areas. ...
This study aimed to analyze the habitat suitability of the endangered Proboscis monkey (Nasalis larvatus) on Borneo using a multi-machine-learning approach. This study integrated physical, vegetational, meteorological, and human activity data to develop a comprehensive habitat suitability model. Four machine-learning algorithms, namely, maximum entropy (MaxEnt), random forest (RF), support vector machine (SVM), gradient tree boosting (GTB), and classification and regression trees (CART), were employed to model the habitat suitability index. A total of 1943 sample points were divided into training (70 %) and validation (30 %) sets for the analysis. This study included three main stages: geospatial database creation, spatial habitat modeling using multi-machine-learning algorithms, and habitat suitability evaluation. In addition, the pressure from human development on the habitat suitability index model was analyzed. This study identified a high level of suitability for Proboscis monkey habitats in nearshore areas. The maximum habitat suitability for Proboscis monkeys was observed to be 11.54 %, as evidenced by the consensus of the MaxEnt value and four machine-learning algorithms. Conversely, the minimum habitat suitability was recorded at 13.27 %, as indicated by disagreement among all algorithms. The AUC values for the machine-learning models ranged from 74 % to 90 %, indicating moderate to high predictive performance. This study provides valuable insights for the formulation of well-planned development programs for Proboscis monkeys. The results of this study will contribute to the accurate identification of potential Proboscis monkey habitats, thereby providing support for conservation efforts aimed at safeguarding this endangered species.
... The proboscis monkey is a primate endemic to Borneo with a limited population distribution only found on the island of Borneo which includes 3 countries, namely Indonesia, Malaysia and Brunei Darussalam [2]. Proboscis monkeys have a spectacular appearance and are easy to observe in the wildlife, making them an excellent tourist attraction [3]. ...
This study was conducted to identify local community perceptions on impacts of proboscis monkey conservation-based ecotourism development in the Curiak Island Area. There were 20 respondents participated in the study. Data were collected through interview to gather information about respondents’ profile and local community perception on socio-cultural and economic impacts of proboscis monkey conservation-based ecotourism development. Data were analysed by using descriptive statistics analysis. The results showed that local community perception on socio-cultural impacts and economic impacts are 4.88 and 4.90 respectively in which are very high category. Therefore, those can be interpreted that the local community perceptions are positive towards the proboscis monkey conservation-based ecotourism development.
... Proboscis monkeys are animals that have benefits as ecotourism attractions [1]. One of the places recognized for proboscis monkey ecotourism is Curiak Island, situated within the Anjir Muara District of Barito Kuala Regency, South Kalimantan. ...
This study was conducted to identify local participation under proboscis monkey conservation-based ecotourism development in Curiak Island Area and the relationship between their socio-demographic characteristics. A total of 20 respondents participated in the study. The data taken included respondents’ profiles and local community participation in proboscis monkey ecotourism development. The data were analyzed by using descriptive statistics analysis and rank Spearman correlation analysis. The results showed that local community participation in proboscis monkey conservation-based ecotourism is at a medium level with an average mean score of 3.34. The correlation coefficient between age and local community participation is −0.223 with a significance value of 0.345 so that it can be said that there is no significant relationship (p>0.05) between age and local community participation and are at a very low category, the correlation coefficient value between gender and local community participation is 0.286 with a significance value of 0.221 so that it can be said that there is no significant relationship (p>0.05) between gender and community participation local and are at a low category, the correlation coefficient value between education and local community participation is 0.296 with a significance value of 0.205 so that it can be said that there is no significant relationship (p>0.05) between education and local community participation and are at a low category, and the correlation coefficient value between income and local community participation is 0.496 with a significance value of 0.026 so that it can be said that there is a real relationship (p<0.05) between income and local community participation and are at a medium category. It can be concluded that local community participation in proboscis monkey conservation-based ecotourism is at a medium level. The socio-demographic characteristic that has a real relationship with local community participation is monthly income. Socio-demographic characteristics that have no significant relationship with local community participation are age, education, and educational background.
... It is also known to have endemic mammalian species, such as the proboscis monkey (Nasalis larvatus), whose population is scattered into sub-populations due to the damage caused by pond development by the local community. Moreover, the Mahakam delta area is an important habitat for proboscis monkeys and their predator of estuarine crocodiles (Crocodillus porosus) [1,2]. ...
Waterbirds are relatively permanent inhabitants of mangrove forests and can come from either the mainland or very distant regions as migrant species. These birds serve as an important indicator for preserving biodiversity in general by maintaining mangrove forests through rehabilitation and restoration activities. Additionally, some species have good economic potential to improve community welfare, as well as current pond products such as fish and shrimp. This study aimed to observe bird species diversity in the mangrove area to understand its function and recognize the migratory species that can be the basis for strengthening preservation or conservation. The research sites were in the Mahakam Delta, which is located in Muara Jawa and Sepatin, Kutai Kartanegara, Indonesia. More than 60 birds were successfully identified. Only one species was classified as CR (critically endangered), namely Thalasseus Bernstein. Meanwhile, bird species that were classified as VU (vulnerable) included Leptotilus javanicus, Fregata minor, and Egretta eulopheutes. Four species, including Anhinga melanogaster, Ichtyopaga ichtyaetus, Macronus ptilosus, and Numenius arquata, were identified as NT (near threatened) species. Most of the species found were characterized as having LC (least concern) status.
... They often are subject to tourism in riparian areas because of their unusual appearance and because they are readily viewable from boats along the river. Proboscis monkeys are Endangered primates that are highly dependent on the riparian tropical forest of Borneo (Agoramoorthy et al., 2004;Bigoni et al., 2003;Lovett & Marshall, 2006;Meijaard & Nijman, 2000). Due to their specialized folivorous digestive system, they often feed in the trees along river banks (Agoramoorthy et al., 2004;Atmoko et al., 2020;Matsuda, Abram, et al., 2020a;Matsuda et al., 2009a;Yeager, 1989). ...
Primate ecotourism is a fast-growing tourism sector that may have a negative effect on wildlife. In riparian areas, tourists can conveniently reach primates via motor boats, but no study has directly examined whether such boats cause stress in primates. Our goal was to test whether the approach of a motor boat induces stress-related and other behaviors in proboscis monkeys ( Nasalis larvatus ), an Endangered species. We studied six one-male, multifemale groups living in a remote riparian area in Sabah, Malaysia, and conducted an experiment by approaching the monkeys in a motor boat by using three conditions with different speeds and travel distances (fast-close, slow-close, and slow-far conditions; 7-8 subjects per condition). For each condition, we compared stress-related behaviors before the boat approach with after the boat started approaching. Feeding, allogrooming and aggression were similarly examined, respectively. We also observed the monkeys’ behaviors at other times to examine age-sex classes differences in vigilance, social proximity, allogrooming, aggression and play (87 subjects). In the experiment, subjects displayed stress-related behaviors for longer in the fast-close and slow-close conditions once the boat started approaching than before the boat approach. The subjects also reduced feeding in the fast-close condition after the boat started approaching. In our observational study, males were more vigilant than females—a behavior that is likely to relate to male-male competition and group protection. This study provides evidence that even a single motor boat moving slowly, with humans behaving calmly, may negatively affect primate behavior and induce stress—an impact that is likely to be larger with tourist boats. Our study also shows that using conditions comparable to the slow-far condition (speed of 3.6 km/hr; no closer than 60 m), where no impact was observed, may help with to develop guidelines for primate tourism in riparian areas. Future research that examines the impact of boats on other primates is needed.
... (Boonratana, 2000). Spesies ini jarang bergerak jauh dari jalur air habitat lokalnya (Erik Meijaard & Nijman, 2000). ...
Puji syukur kehadirat Allah SWT, Tuhan Yang Maha Esa, Buku Ajar ECOEDUTOURISM (Model Penataan Kawasan Lahan Gambut Studi di Kawasan Pengelolaan Hutan (KPH) Kayu Tangi Kalimantan Selatan) dapat penulis selesaikan. Buku ini hadir sebagai wujud tanggungjawab atas profesi akademik sebagai dosen Geografi dalam mengemban misi mencerdaskan kehidupan bangsa. Buku Ajar ini menguraikan 6 (enam) bab pembahasan diantaranya; (1) Ecoedutourism; (2) Kawasan Pengelolaan Hutan; (3) Tipologi Kawasan; (4) Pengembangan Kawasan Pengelolaan Hutan; (5) Rencana Zonasi dan Tapak Kawasan Pengelolaan Hutan; (6) Kesiapan stakeholder dalam penataan ruang KPH Kayu Tangi berbasis ecoedutourism. Buku ajar ini selain memperkaya bacaan buku teks yang sudah ada juga mempunyai keunggulan dilengkapi dengan kompetensi yang akan dicapai mahasiswa (learning outcome), evaluasi, dan lembar kerja pada masing-masing pembahasan materi, yang disesuaikan dengan Rencana Pembelajaran Semester (RPS) matakuliah. Buku Ajar ini menjadi sangat bermanfaat bagi para mahasiswa yang mengambil bidang atau program studi Geografi, Semoga dengan kehadiran buku ajar ini semakin memperkaya dan memperluas wawasan dan pengetahuan para geografer dalam berkontribusi dalam pembangunan.
... Previous studies on the proboscis monkey focused on the population, conservation, feeding ecology, and social dynamics of this species (4,12,15). Studies pertaining to its reproduction mainly shed light on the behaviour, breeding ecology, and breeding seasonality (17), and no literature was found on the spermatology of N. larvatus. Sperm morphology, motility and concentration are considered the three most important parameters when assessing semen quality. ...
Introduction
The proboscis monkey ( Nasalis larvatus ) is an endangered species with a declining population. This article describes the first successful attempt at sperm collection and evaluation, and the testicular and sperm morphometries of the wild proboscis monkey in Sabah, Malaysia.
Material and Methods
Eight semen collection procedures using electro-ejaculation and digital manipulation were conducted in three wild adult male proboscis monkeys. A total of 21 ejaculates were collected. The testicular biometry was measured with the aid of ultrasonography. Sample evaluation included semen volume and pH and sperm concentration, viability, and abnormality. The sperm morphometry was undertaken using phase contrast microscopy.
Results
The mean (±SD) total testicular volume of these animals was 5.77 cm ³ (±1.58). Semen collection by electro-ejaculation resulted in an 84% success rate, while digital manipulation did not result in any ejaculation. Each animal showed different semen characteristics, where the volume was 5–540 μL, pH 8–9, and sperm concentration 0.041–83.00 ×106/mL. The percentage of abnormal sperm was high at 76.8% (±89.60), largely due to midpiece abnormality. Normal sperm had a spherical head and long tail with a head : midpiece : tail length ratio of 1 : 2: 8.
Conclusion
The social status of these animals may contribute to the generally low quality of the semen. The techniques and data from this study are useful for future conservation and application of assisted reproductive technology in this species.
... One of the priority areas for the conservation of proboscis monkeys is the Mahakam River [5], with Kedang Kepala River as one of its tributaries, and Kenohan-Suwi Wetland is upstream. The Suwi River and its surrounding wetlands play an essential role in regulating the hydrological balance and habitat of the endangered species. ...
Suwi River, which is a part of Kenohan-Suwi Wetland in East Kutai District, East Kalimantan is a habitat of endangered animals such as proboscis monkey ( Nasalis larvatus ). Therefore, this study aims to determine the habitat, distribution, threats, and conservation efforts of proboscis monkeys in the Suwi River. To achieve this, the boat survey method was adopted, while plot line samples were used for vegetation analysis. The results showed that the habitat is composed of riverine plant species, such as prupuk ( Mallotus sumatranus ; IV=121.84%), bungur ( Lagerstroemia speciosa ; IV=37.10%), and rengas ( Gluta renghas ; IV=34.76%). Furthermore, a minimum of 12 monkey groups was distributed in this area, however, their population is unknown. Illegal hunting by local people has caused population decline, this is in addition to other threats, such as habitat conversion, forest fire, and invasive plant species. The effort to protect the habitat of proboscis monkeys was made by developing Essential Ecosystem Areas Suwi-Mesangat. Other institutions that committed to protecting this area include Federal and local government, NGO, local community, and palm oil company
... Proboscis monkeys are closely associated with waterways and inhabit mainly riverine forests, mangrove, and lowland peat swamps (Sha et al., 2008). However, such habitats are becoming increasingly threatened by the conversion to industrial agricultural plantations, mainly oil palm, which requires these same lowland floodplain areas (Meijaard & Nijman, 2000a;Gaveau et al., 2014). As a result, agricultural expansion and forest fragmentation have been shown to exert considerable negative impacts on proboscis monkey population size and distribution island-wide (Meijaard & Nijman, 2000b;Matsuda et al., 2020;Toulec et al., 2020). ...
Proboscis monkey (Nasalis larvatus) habitats throughout its range are becoming increasingly fragmented and degraded. Discerning patterns of abundance and distribution, and elucidating factors that affect the survival of this species in altered landscapes are vital for its conservation. We assessed population trends over 10 years in the Klias Peninsula of western Sabah, Malaysian Borneo. Our findings revealed that population size and distribution remained generally stable between 2004 and 2014, and little further habitat loss occurred over this interval. However, a positive correlation in proboscis monkey abundance was found with increasing proximity to areas where more
large emergent trees remained along the riverbanks. This indicates that habitat quality is an ongoing conservation concern. Furthermore, we found that only about half of the available proboscis monkey habitat in this region is fully protected. The rest is within commercial and native-titled lands that are, by law, required to be converted to agriculture. For example, we identified key proboscis monkey habitat within and around the Padas Damit Class IV Amenity Forest Reserve, an area where we also found the highest densities of proboscis monkeys in the region. However, significant areas in close proximity or contiguous with this forest reserve have subsequently been converted to oil palm. Such development not only causes outright habitat loss but also risks disrupting connectivity of proboscis monkey habitat, especially along rivers. This in turn poses a threat not only to long-term viability of the local proboscis monkey population, but also to another vital aspect of the economy of the Klias region that depends on the draw of proboscis monkey-viewing for wildlife-based tourism. We suggest that mechanisms to
safeguard the contiguity of remaining proboscis monkey habitat within this area should be implemented at the landscape level to ensure persistence of the local population.
... Bekantan (Nasalis larvatus Wrumb.) merupakan salah satu satwa endemik pulau Kalimantan yang dilindungi di Indonesia karena populasinya kian menurun akibat kerusakan habitat dan perburuan liar.Secara internasional, bekantan termasuk dalam daftar Appendix I CITES (Erik Meijaard & Nijman, 2000b, 2000a dan berdasarkan Red Data Book IUCN, sejak tahun 2000 masuk dalam kategori endangered species (E. Meijaard, Nijman, & Supriatna, 2008). ...
... The habitat loss rate is estimated at 2% per year [4]; currently only 55% of the original 121,670 km 2 proboscis monkey habitat remains. Eleven percent of its habitat is located in conservation [5] and only 9% of is in protected areas [6]. The destruction of their habitat can result in habitat fragmentation and isolated populations in small areas. ...
The proboscis monkey is an endangered primate endemic to Borneo. Most of their habitats are outside conservation areas and are under threat from conversion to other land uses, such as those found in the Berau Delta. Habitat loss and destruction significantly affect the quality and viability of the proboscis monkey population. This study aims to determine land cover and proboscis monkey habitat types in Berau Delta. Land cover was obtained from the interpretation of the Lansat 8 OLI 2019 satellite image. Vegetation data were collected using a line plot transect method and continued with cluster analysis. The results showed that mangrove forest has the largest coverage (35.92%), followed by secondary forest (17.10%) and riparian forest (12.96%). At least 74 species of woody plants belonging to 61 genera and 37 families in a 2.4 ha observation plot. The range of species diversity index was from 0.80 to 2.88, and; evenness index values range from 0.58 to 0.82. The habitat was categorized into two main clusters: mangrove cluster (Buasin Cape, Guntung Estuary) and riverine cluster (Lati River, Saodang Kecil Island, Batu-Batu, Bebanir Lama). The mangrove forest habitat consists of Rhizophora mucronata, R. apiculata, Bruguiera sp, Sonneratia alba, and Avicennia alba. The riparian habitats are dominated by Sonneratia caseolaris, Vitex pinnata, Cerbera manghas, Brownlowia argentata, Heritiera littoralis, Syzygium lineatum, Nauclea officinalis, Xylocarpus
granatum, Syzygium sp.1, and A. alba. The average of total and lower branches height of trees in the Lati River and Basin Cape were higher than in other habitats, forming a continuous canopy.
Long-term monitoring data on population abundance and distribution are essential for developing and refining conservation strategies, particularly for endangered species like the proboscis monkey (Nasalis larvatus), for which data remain limited across much of their range in Borneo. Previous studies conducted in 2004/2005 and 2014 in the Klias Peninsula, western Sabah, northern Borneo, provided important insights into population trends and distribution. Building on this foundation, we reassessed the proboscis monkey population in 2022 after an 8-year interval and investigated changes in land use and land cover during the same period. Our findings indicate a lower overall estimate of population abundance (number of individuals); however, the number of observed groups is comparable to previous studies, suggesting some stability. Distribution patterns have remained relatively stable, with population strongholds in the central part of the Klias Peninsula, underscoring the continued importance of areas like Padas Damit Forest Reserve for proboscis monkey conservation. Our data also reveal concerning trends, including a decline in group sizes (number of individuals per group) within breeding units and the presence of very small populations in fragmented sites such as Bongawan, presenting ongoing conservation challenges. Our land-use and land-cover change findings further revealed that less than half of the available proboscis monkey habitats in this region are fully protected. Vegetation analysis showed that tree species richness positively influences proboscis monkey abundance, emphasizing the critical role of food resource diversity. These findings have important conservation implications for the long-term survival of this endangered primate in the Klias Peninsula region.
Proboscis monkeys are largely confined along the eastern coastal zone of Sabah, Malaysia. Sulaman Lake Forest Reserve (SLFR) is the only Class V Mangrove Forest Reserve in the forestry district of Kota Kinabalu, Sabah. This study is in accordance with the conservation strategies outlined in the Sabah Proboscis Monkey Action Plan (2019–2028), which is to focus on areas that have not been surveyed. Prior to this study, the status of proboscis monkeys in this reserve had not been scientifically documented. In addition, the habitat of this colobine species along the coastal zone of Sulaman Bay will be impacted by the construction of Pan Borneo Highway (Work Package 9). Hence, we intend to shed light on the status of proboscis monkeys in the SLFR including local threats to their population. This study discovered a small and isolated relict population of proboscis monkeys through a boat survey approach, which was also derived from interview sessions with local communities. We found that the degradation of mangrove forest integrity is a major threat to this population in the SLFR. It is hoped that this study would trigger more research, especially population size estimation because such baseline information is crucial in the formulation of effective conservation programmes.
Bekantan (Nasalis larvatus Wurm, 1787) adalah primata endemik Borneo yang dikategorikan sebagai spesies terancam punah oleh IUCN dan dilindungi oleh peraturan nasional. Populasi bekantan telah mengalami penurunan signifikan di berbagai habitat, termasuk di Cagar Alam Teluk Adang yang berbagi ruang dengan aktivitas manusia. Identifikasi faktor-faktor yang mempengaruhi habitat yang cocok bagi bekantan dalam sebaran spasial sangat penting untuk menentukan tindakan konservasi yang tepat untuk melindungi populasi bekantan di Cagar Alam Teluk Adang. Penelitian ini bertujuan 1) Menghasilkan peta kesesuaian habitat melalui model hubungan antara keberadaan bekantan dengan variabel lingkungan yang berpengaruh dan 2) Memetakan struktur habitat berdasarkan pada hasil peta kesesuaian habitat. Penelitian ini menggunakan Model MaxEnt untuk membangun prediksi distribusi bekantan berdasarkan data perjumpaan dan sepuluh variabel lingkungan. Hasil kesesuaian habitat kemudian dianalis menggunakan metode Analisis Morphological Spatial Pattern Analysis (MSPA) untuk menghasilkan struktur habitat. Berdasarkan hasil penelitian melalui Maxent, faktor-faktor lingkungan yang berpengaruh terhadap kehadiran bekantan adalah hutan mangrove, jarak dari sungai, jarak dari garis pantai dan Leaf Area Index. Hasil klasifikasi juga menunjukan luas potensi habitat bekantan adalah sekitar 7.513 Ha (15.7% dari total luasan). Habitat bekantan telah mengalami fragmentasi dengan 11 inti utama yang dapat secara utuh mengakomodasi home range bekantan.
Background
One of the constrain in proboscis monkey ( Nasalis larvatus ) conservation is gastrointestinal helminth (GH) infection. Here, we conducted a study to determine the prevalence of GHs in captive proboscis monkeys in Surabaya Zoo, Indonesia.
Methods
Twenty fecal samples were collected from three groups (i.e., nursery cage [NC] [ n = 1], communal show cage [SC] [ n = 8], and free‐ranging colonies [FC] [ n = 11]). The fecal samples have been examined through McMaster and sugar floatation techniques.
Results
The total prevalence of GH infection was 85.00% (17/20). We confirmed infection of Trichuris sp., Ascaris sp., Strongyloides sp., and Hymenolepis nana with Trichuris eggs was dominant. Although the prevalence of infection was high, the number of eggs per gram (epg) was low.
Conclusion
GH infection in captive proboscis monkeys in Surabaya Zoo, Indonesia, is highly prevalent. These results were useful for future research, control, and prevention of zoonotic potency purposes.
Habitat loss and degradation are currently the main anthropogenic causes of species extinctions. The root cause is human overpopulation. This unique volume provides, for the very first time, a comprehensive overview of all threatened and recently extinct mammals, birds, reptiles, amphibians, and fishes within the context of their locations and habitats. The approach takes a systematic examination of each biogeographic realm and region of the world, both terrestrial and marine, but with a particular emphasis on geographic features such as mountains, islands, and coral reefs. It reveals patterns useful in biodiversity conservation, helps to put it all into perspective, and ultimately serves as both a baseline from which to compare subsequent developments as well as a standardization of the way threatened species are studied.
The Colobines are a group of Afroeurasian monkeys that exhibit extraordinary behavioural and ecological diversity. With long tails and diverse colourations, they are medium-sized primates, mostly arboreal, that are found in many different habitats, from rain forests and mountain forests to mangroves and savannah. Over the last two decades, our understanding of this group of primates has increased dramatically. This volume presents a comprehensive overview of the current research on colobine populations, including the range of biological, ecological, behavioural and societal traits they exhibit. It highlights areas where our knowledge is still lacking, and outlines the current conservation status of colobine populations, exploring the threats to their survival. Bringing together international experts, this volume will aid future conservation efforts and encourage further empirical studies. It will be of interest to researchers and graduate students in primatology, biological anthropology and conservation science. Additional online resources can be found at www.cambridge.org/colobines.
The flora and fauna of Southeast Asia are exceptionally diverse. The region includes several terrestrial biodiversity hotspots and is the principal global hotspot for marine diversity, but it also faces the most intense challenges of the current global biodiversity crisis. Providing reviews, syntheses and results of the latest research into Southeast Asian earth and organismal history, this book investigates the history, present and future of the fauna and flora of this bio- and geodiverse region. Leading authorities in the field explore key topics including palaeogeography, palaeoclimatology, biogeography, population genetics and conservation biology, illustrating research approaches and themes with spatially, taxonomically and methodologically focused case studies. The volume also presents methodological advances in population genetics and historical biogeography. Exploring the fascinating environmental and biotic histories of Southeast Asia, this is an ideal resource for graduate students and researchers as well as environmental NGOs.
The flora and fauna of Southeast Asia are exceptionally diverse. The region includes several terrestrial biodiversity hotspots and is the principal global hotspot for marine diversity, but it also faces the most intense challenges of the current global biodiversity crisis. Providing reviews, syntheses and results of the latest research into Southeast Asian earth and organismal history, this book investigates the history, present and future of the fauna and flora of this bio- and geodiverse region. Leading authorities in the field explore key topics including palaeogeography, palaeoclimatology, biogeography, population genetics and conservation biology, illustrating research approaches and themes with spatially, taxonomically and methodologically focused case studies. The volume also presents methodological advances in population genetics and historical biogeography. Exploring the fascinating environmental and biotic histories of Southeast Asia, this is an ideal resource for graduate students and researchers as well as environmental NGOs.
The flora and fauna of Southeast Asia are exceptionally diverse. The region includes several terrestrial biodiversity hotspots and is the principal global hotspot for marine diversity, but it also faces the most intense challenges of the current global biodiversity crisis. Providing reviews, syntheses and results of the latest research into Southeast Asian earth and organismal history, this book investigates the history, present and future of the fauna and flora of this bio- and geodiverse region. Leading authorities in the field explore key topics including palaeogeography, palaeoclimatology, biogeography, population genetics and conservation biology, illustrating research approaches and themes with spatially, taxonomically and methodologically focused case studies. The volume also presents methodological advances in population genetics and historical biogeography. Exploring the fascinating environmental and biotic histories of Southeast Asia, this is an ideal resource for graduate students and researchers as well as environmental NGOs.
The flora and fauna of Southeast Asia are exceptionally diverse. The region includes several terrestrial biodiversity hotspots and is the principal global hotspot for marine diversity, but it also faces the most intense challenges of the current global biodiversity crisis. Providing reviews, syntheses and results of the latest research into Southeast Asian earth and organismal history, this book investigates the history, present and future of the fauna and flora of this bio- and geodiverse region. Leading authorities in the field explore key topics including palaeogeography, palaeoclimatology, biogeography, population genetics and conservation biology, illustrating research approaches and themes with spatially, taxonomically and methodologically focused case studies. The volume also presents methodological advances in population genetics and historical biogeography. Exploring the fascinating environmental and biotic histories of Southeast Asia, this is an ideal resource for graduate students and researchers as well as environmental NGOs.
Primate tourism is a growing phenomenon, with increasing pressure coming from several directions: the private sector, governments, and conservation agencies. At the same time, some primate sites are working to exclude or severely restrict tourism because of problems that have developed as a result. Indeed, tourism has proven costly to primates due to factors such as disease, stress, social disruption, vulnerability to poachers, and interference with rehabilitation and reintroduction. Bringing together interdisciplinary expertise in wildlife/nature tourism and primatology, experts present and discuss their accumulated experience from individual primate sites open to tourists, formal studies of primate-focused tourism, and trends in nature and wildlife tourism. Chapters offer species- and site-specific assessments, weighing conservation benefits against costs, and suggesting strategies for the development of informed guidelines for ongoing and future primate tourism ventures. Primate Tourism has been written for primatologists, conservationists and other scientists. It is also relevant to tourists and tourism professionals.
Primate tourism is a growing phenomenon, with increasing pressure coming from several directions: the private sector, governments, and conservation agencies. At the same time, some primate sites are working to exclude or severely restrict tourism because of problems that have developed as a result. Indeed, tourism has proven costly to primates due to factors such as disease, stress, social disruption, vulnerability to poachers, and interference with rehabilitation and reintroduction. Bringing together interdisciplinary expertise in wildlife/nature tourism and primatology, experts present and discuss their accumulated experience from individual primate sites open to tourists, formal studies of primate-focused tourism, and trends in nature and wildlife tourism. Chapters offer species- and site-specific assessments, weighing conservation benefits against costs, and suggesting strategies for the development of informed guidelines for ongoing and future primate tourism ventures. Primate Tourism has been written for primatologists, conservationists and other scientists. It is also relevant to tourists and tourism professionals.
Primate tourism is a growing phenomenon, with increasing pressure coming from several directions: the private sector, governments, and conservation agencies. At the same time, some primate sites are working to exclude or severely restrict tourism because of problems that have developed as a result. Indeed, tourism has proven costly to primates due to factors such as disease, stress, social disruption, vulnerability to poachers, and interference with rehabilitation and reintroduction. Bringing together interdisciplinary expertise in wildlife/nature tourism and primatology, experts present and discuss their accumulated experience from individual primate sites open to tourists, formal studies of primate-focused tourism, and trends in nature and wildlife tourism. Chapters offer species- and site-specific assessments, weighing conservation benefits against costs, and suggesting strategies for the development of informed guidelines for ongoing and future primate tourism ventures. Primate Tourism has been written for primatologists, conservationists and other scientists. It is also relevant to tourists and tourism professionals.
Primate tourism is a growing phenomenon, with increasing pressure coming from several directions: the private sector, governments, and conservation agencies. At the same time, some primate sites are working to exclude or severely restrict tourism because of problems that have developed as a result. Indeed, tourism has proven costly to primates due to factors such as disease, stress, social disruption, vulnerability to poachers, and interference with rehabilitation and reintroduction. Bringing together interdisciplinary expertise in wildlife/nature tourism and primatology, experts present and discuss their accumulated experience from individual primate sites open to tourists, formal studies of primate-focused tourism, and trends in nature and wildlife tourism. Chapters offer species- and site-specific assessments, weighing conservation benefits against costs, and suggesting strategies for the development of informed guidelines for ongoing and future primate tourism ventures. Primate Tourism has been written for primatologists, conservationists and other scientists. It is also relevant to tourists and tourism professionals.
Primate tourism is a growing phenomenon, with increasing pressure coming from several directions: the private sector, governments, and conservation agencies. At the same time, some primate sites are working to exclude or severely restrict tourism because of problems that have developed as a result. Indeed, tourism has proven costly to primates due to factors such as disease, stress, social disruption, vulnerability to poachers, and interference with rehabilitation and reintroduction. Bringing together interdisciplinary expertise in wildlife/nature tourism and primatology, experts present and discuss their accumulated experience from individual primate sites open to tourists, formal studies of primate-focused tourism, and trends in nature and wildlife tourism. Chapters offer species- and site-specific assessments, weighing conservation benefits against costs, and suggesting strategies for the development of informed guidelines for ongoing and future primate tourism ventures. Primate Tourism has been written for primatologists, conservationists and other scientists. It is also relevant to tourists and tourism professionals.
Primate tourism is a growing phenomenon, with increasing pressure coming from several directions: the private sector, governments, and conservation agencies. At the same time, some primate sites are working to exclude or severely restrict tourism because of problems that have developed as a result. Indeed, tourism has proven costly to primates due to factors such as disease, stress, social disruption, vulnerability to poachers, and interference with rehabilitation and reintroduction. Bringing together interdisciplinary expertise in wildlife/nature tourism and primatology, experts present and discuss their accumulated experience from individual primate sites open to tourists, formal studies of primate-focused tourism, and trends in nature and wildlife tourism. Chapters offer species- and site-specific assessments, weighing conservation benefits against costs, and suggesting strategies for the development of informed guidelines for ongoing and future primate tourism ventures. Primate Tourism has been written for primatologists, conservationists and other scientists. It is also relevant to tourists and tourism professionals.
Primate tourism is a growing phenomenon, with increasing pressure coming from several directions: the private sector, governments, and conservation agencies. At the same time, some primate sites are working to exclude or severely restrict tourism because of problems that have developed as a result. Indeed, tourism has proven costly to primates due to factors such as disease, stress, social disruption, vulnerability to poachers, and interference with rehabilitation and reintroduction. Bringing together interdisciplinary expertise in wildlife/nature tourism and primatology, experts present and discuss their accumulated experience from individual primate sites open to tourists, formal studies of primate-focused tourism, and trends in nature and wildlife tourism. Chapters offer species- and site-specific assessments, weighing conservation benefits against costs, and suggesting strategies for the development of informed guidelines for ongoing and future primate tourism ventures. Primate Tourism has been written for primatologists, conservationists and other scientists. It is also relevant to tourists and tourism professionals.
Primate tourism is a growing phenomenon, with increasing pressure coming from several directions: the private sector, governments, and conservation agencies. At the same time, some primate sites are working to exclude or severely restrict tourism because of problems that have developed as a result. Indeed, tourism has proven costly to primates due to factors such as disease, stress, social disruption, vulnerability to poachers, and interference with rehabilitation and reintroduction. Bringing together interdisciplinary expertise in wildlife/nature tourism and primatology, experts present and discuss their accumulated experience from individual primate sites open to tourists, formal studies of primate-focused tourism, and trends in nature and wildlife tourism. Chapters offer species- and site-specific assessments, weighing conservation benefits against costs, and suggesting strategies for the development of informed guidelines for ongoing and future primate tourism ventures. Primate Tourism has been written for primatologists, conservationists and other scientists. It is also relevant to tourists and tourism professionals.
Primate tourism is a growing phenomenon, with increasing pressure coming from several directions: the private sector, governments, and conservation agencies. At the same time, some primate sites are working to exclude or severely restrict tourism because of problems that have developed as a result. Indeed, tourism has proven costly to primates due to factors such as disease, stress, social disruption, vulnerability to poachers, and interference with rehabilitation and reintroduction. Bringing together interdisciplinary expertise in wildlife/nature tourism and primatology, experts present and discuss their accumulated experience from individual primate sites open to tourists, formal studies of primate-focused tourism, and trends in nature and wildlife tourism. Chapters offer species- and site-specific assessments, weighing conservation benefits against costs, and suggesting strategies for the development of informed guidelines for ongoing and future primate tourism ventures. Primate Tourism has been written for primatologists, conservationists and other scientists. It is also relevant to tourists and tourism professionals.
Primate tourism is a growing phenomenon, with increasing pressure coming from several directions: the private sector, governments, and conservation agencies. At the same time, some primate sites are working to exclude or severely restrict tourism because of problems that have developed as a result. Indeed, tourism has proven costly to primates due to factors such as disease, stress, social disruption, vulnerability to poachers, and interference with rehabilitation and reintroduction. Bringing together interdisciplinary expertise in wildlife/nature tourism and primatology, experts present and discuss their accumulated experience from individual primate sites open to tourists, formal studies of primate-focused tourism, and trends in nature and wildlife tourism. Chapters offer species- and site-specific assessments, weighing conservation benefits against costs, and suggesting strategies for the development of informed guidelines for ongoing and future primate tourism ventures. Primate Tourism has been written for primatologists, conservationists and other scientists. It is also relevant to tourists and tourism professionals.
This book offers a comprehensive account of the current state of inland waters in tropical and subtropical East Asia, exploring a series of case studies of freshwater fish, reptiles, amphibians, birds, mammals and water bodies at particular risk. The book highlights the rich freshwater biodiversity of tropical East Asia and draws attention to the various threats it faces due to human activities and rapid environmental change. It addresses the question of whether the contributions of these animals and habitats, or biodiversity in general, to ecosystem functioning and service provision provide sufficient basis for arguments supporting nature conservation. Drawing on instances from the rivers and lakes of tropical East Asia, the book also asks whether the benefits accruing from intact ecosystems are likely to be enough to ensure their preservation. If the answer to either or both these questions is ʼno’, then what are the prospects for freshwater biodiversity in rapidly changing tropical East Asia? This book will be of interest to students and scholars of biodiversity, conservation, freshwater ecology, ecosystem services and Asian Studies.
Mangroves are one of the most potential tidal wetlands characterized by their hydrological, ecological, and geological features. They form the diversified and biologically productive ecosystem, populated with heterogeneous groups of plant taxonomy. The transboundary Sundarban mangrove wetland (89°02′ to 89°55′E and 21°30′ to 22°30′N) is situated on the Ganges–Brahmaputra–Meghna river network. This represents the largest continuous tract of mangrove forest in the world, spanning across Bangladesh (62%) and India (38%). The chapter gives an illustrative account of the diversity and distribution patterns of mangroves in India and other coastal regions across the world, along with their anomalous biogeographical patterns, mangrove landform classification and their morphological structure and adaptation strategies. In addition, the mangrove ecosystem goods and services, carbon storage efficiency and application of remote sensing for mangrove mapping have been discussed. A haven for rich biodiversity, Sundarban harbors several rare and globally threatened plants and animals. The overall common key threats for mangrove ecosystems are land-use changes, overexploitation of natural resources, chemical pollution from point and diffusive sources, reduced freshwater supply and silt deposition. Both India and Bangladesh should implement bilateral monitoring programs to resolve those emerging problems and formulate necessary management strategies to restore this diversified and iconic mangrove ecosystem.
A recent update of biodiversity in Wehea-Kelay Landscape. 500k ha of landscape mapped, more than 500 animals and 700 plants identified. Home of critically endangered Bornean orangutans, the largest population in East Kalimantan in the outside conservation areas.
Proboscis monkeys, endemic to the island of Borneo, are declining in Sarawak. Their mangrove and peat swamp forest habitats are being degraded or destroyed and people continue to hunt them despite their protected status. Surveys between 1984 and 1986 established the status of this monkey and its habitats in this Malaysian state. The author who participated in the surveys, receiving some financial support from the Oryx 100% Fund, discusses the results and makes recommendations for future conservation action.
The status of the proboscis monkey Nasalis larvatus Wurmb. was assessed within the Malaysian State of Sarawak by means of boat surveys at selected sites during 1980–1981, through interviews with residents and by searches of Forest Department files for locality records. The species is widely distributed, mainly in coastal areas, but there are broad discontinuities in its range. Areas occupied by proboscis monkeys are covered primarily by mangrove forests, riparian forests and associated vegetation types. Indices of abundance are highest in mangrove/high forest complexes along the coast and in riparian forests, and lowest in extensive stands of mangrove. Much of the area occupied by proboscis monkeys is subject to logging, agriculture and settlement, which generally lead to local reductions of monkey population densities. Some hunting occurs. About 10% of the total State population of this species is found in officially gazetted protected areas, but additional areas are required to increase the extent and diversity of protected habitat.
Kutai National Park in East Kalimantan was originally established as a game reserve in 1936 and became a national park in 1982. The park's lowland forests have suffered from logging, agricultural encroachment and extensive fires during the prolonged dry season in 1982 and 1983. During the 1980s a new coal mine opened at Sangatta to exploit rich coal deposits along the northern boundary of the park. The new mine could have been the ‘last straw’ for Kutai. Instead, industrial development has provided a new and exciting opportunity to strengthen park protection and management.
The endemic proboscis monkeys in Borneo live along the rivers and coasts where people also tend to concentrate. Hitherto there has been room for both. But in Kalimantan, logging and wood-processing industries are expanding rapidly — Indonesia hopes to be self-sufficient in pulp and paper by 1984 — and this, together with the planned removal by the same date of 2½ million people from overcrowded Java, mostly to Kalimantan, could seriously affect the proboscis.
Rain forests in Central Kalimantan, Borneo, are under increasing pressure from commercial industry, agricultural projects and transmigration programmes. Our knowledge of the hill forests in central Borneo is virtually non-existent, yet they may disappear before we realize their true value as intact forests. These rapid developments prompted the FFPS to launch the Red Alert Project, which, together with Project Barito Ulu, is investigating ways to promote rain-forest conservation in Kalimantan, Indonesia.
Proboscis monkey (Nasalis larvatus) social organization was studied at the Natai Lengkuas station, Tanjung Puting National Park in Kalimantan Tengah, Indonesia. Data were collected on ten one-male groups and two all-male groups using scan sampling and event sampling during follows, and through evening census surveys. Proboscis monkeys were found to form stable one-male groups. Specific groups associated at their sleeping sites, in a manner similar to the fission-fusion pattern described for hamadryas and gelada baboons. Analyses performed on these associations indicated that the groups formed two separate bands. These separate bands appear to be a secondary level of organization, distinct from the primary level of organization, the one-male and all-male groups. This is the first evidence for such a two-tiered system of organization in an arboreal colobine species. Proboscis monkeys closely resemble gelada baboons in their organizational pattern. In both species, adult females direct the majority of their affiliative behavior towards their offspring and other adult females, males do not engage in active herding, all-male groups are present, and one-male groups do spend time apart from other groups. Home ranges of both groups and of bands of proboscis monkeys overlapped extensively; temporal avoidance between bands may have been mediated by early morning vocalizations and branch shaking displays.
Proboscis monkey (Nasalis larvatus) socioecology was studied at the Natai Lengkuas Station, Tanjung Puting National Park, in Kalimantan Tengah, Indonesia. Data on the nature of intergroup interactions were collected on ten one-male groups and two all-male groups using event sampling during follows and also through evening census surveys. Proboscis monkeys form stable one-male groups, with specific groups regularly associating at their sleeping sites (band members). Both intraband and interband high-intensity agonistic displays (slapping, chasing, biting) were rare. Lower intensity agonistic displays (vocalizations, leaping-branch shaking, and erect penis and open-mouth displays) occurred frequently. Temporal avoidance between bands may have been mediated by early morning vocalizations and branch shaking displays by the adult males. Associations between groups may play a role in displacement avoidance and/or predation avoidance.
Studies on the ecology of the proboscis monkey were conducted in seven areas of Sarawak during 1980–1981. Groups were found
in a variety of riparian and coastal habitats but where high forests occurred they appeared to be preferred over other adjacent
types. Undisturbed tidal forests were widely used but were preferred only where high forest was lacking or limited in extent.
Clear-felled tidal forests and areas around human settlements were completely avoided, although some use was made of selectively
felled tidal forests, remnant tidal forests adjacent to agricultural land, and selectively logged high forest. Monkeys slept
primarily and perhaps exclusively along river edges where these were available, moving inland up to 750m during the day and
returning to the riverside in late afternoon. Groups often split up into distinct subunits during daily movements. Feeding
occurred throughout the day and in all habitats occupied. Proboscis monkeys were observed feeding on at least 90 plant species,
including leaves or shoots of 75 species, fruits of 15 species, seeds of 10 species, and flowers of 4 species. Certain tidal
forest species (Sonneratia alba, Avicennia alba, Bruguiera gymnorrhiza, Rhizophora spp.) appeared to be the single most important food plants, although where high forests were available more feeding time
was spent in these types than in tidal forests or other habitats.
Proboscis monkeys,Nasalis larvatus (Wurmb), were investigated in the Padas Bay and Kinabatangan River areas, Sabah, from July 1968 to March 1969. The proboscis monkey is a common, widely distributed species of coloboids in Sabah, living in the various vegetations that extend from the coastal swamp to the inland plain. It appears to have a terrestrial tendency, compared with other coloboids, moving around on the ground in the forest and extending its activity, sometimes, to the open land along the river beach. The number of monkey in a troop, we observed, ranged from 11 to 32, and almost all troops were composed of several adult males, many more adult females, and immature animals. The adult males appear to play the role of leaders in the troop through their characteristic behavior, attacking, threatening, warning, watching, etc., other troop members or invaders. Each troop always emitted various boisterous vocalizations which were divided into 14 types.
The social structure of proboscis monkeys (Nasalis larvatus) was investigated in the Brunei Bay area of Brunei Darussalam (Northern Borneo). Intraspecific variability in social systems
had been suggested to occur in this species, with social structure varying with habitat differences. Prior reports for this
area suggested that groups contained several males, females, and offspring and were unstable. Contrary to these reports, I
found that the monkeys were organized into groups containing one male, several females, and offspring. These groups associated
at sleeping sites at the river’s edge, thus forming a secondary level of organization. This is the same social system reported
in Sarawak, Malaysia and Kalimantan, Indonesia in different habitat types. It appears that methodological differences may
account for the discrepancies between reports. I have found no evidence to suggest that intraspecific variation in social
systems occurs in this species.
Data are presented from a 16-month study of proboscis monkeys in an area of mixed coastal forest in Sarawak. The population
density, social organization, and feeding and ranging behavior are described in detail. Results are compared with those from
other primates in an attempt to understand why females of certain species (including proboscis monkeys) transfer between social
groups. The scarcity of available food and reasons for the limited habitat preferences of proboscis monkeys are also discussed.
"There have been several major research efforts on the rate and causes of Indonesia 's deforestation in recent years and much associated literature, but there is still no consensus in the research community on these issues. This paper reviews the areas of uncertainty and confusion, and proposes questions that must be answered to get a better grasp of the subject. Among the key questions are: (1) How are we to define 'forest', 'deforestation' and 'agency' in the context of Indonesia?; (2) What are the socio-economic characteristics and land-use practices of the various agents that have been lumped under the term 'shifting cultivation'?; (3) Is the relationship between increasing population density and loss of forest cover causal or incidental?, (4) Why do some concessionaires appear to manage their sites relatively well, while many others do not?; (5) What have been the net forest cover effects of macro-economic restructuring and changes of commodity prices since the early 1980s? Guidelines are proposed for improved research on the rate and causes of forest cover change. The paper closes noting the need to rise above a tendency to seek mono-causal explanations. Cogent explanations will necessarily be complex, since the causes reside in long-standing and broad socio-economic forces."
2 maps, in pocket, scale: 1:1,000,000 Map(s) inclu.
Validation of observations is an important part of any remote sensing program. With respect to aerosols this is exceedingly difficult because each technique typically measures a different aerosol parameter. Correlative sensors, therefore, must be capable of measuring the same parameter over the same size range or include enough measurements to properly characterize the aerosol, possibly with the assistance of models. In any correlative measurement program, simultaneity in space and time is required. This can be less restrictive during periods of atmospheric stability. The discussion is presented which is focused on the validation programs developed for NASA's Stratospheric Aerosol Measurement (SAM II), and the Stratospheric Aerosol and Gas Experiments I and II (SAGE I and II). To date these were limited to the stratosphere. Since satellite sensors are capable of providing near-global and long-term observations, periodic correlative observations over various global locations and seasons are required for assuring that data quality is unchanged, or for understanding any changes observed.
A brief survey was conducted in East Kalimantan, Indonesia, to determine the influence of selective logging operations on primate populations. Data were also collected on some birds and squirrels. Selective logging that causes only moderate habitat disturbance does not seem to result in a significant decrease in the densities of several primate species. Whereas some species adjust readily to moderately disturbed habitats, other species may have difficulty in maintaining a breeding population in logged areas. A review of the literature plus our own data suggest that rain forest birds and squirrels seem to be the most disrupted by selective logging of their habitats. While some of the other mammals are directly harmed by selective logging, others are endangered only by the human encroachment that often follows. Suggestions regarding enlightened tropical forestry practices, additional studies of the influence of selective logging, and the establishment of forest preservation areas are also discussed.
Proboscis monkeys, Nasalis larvatus, were observed from a boat in coastal mangrove swamps in Brunei. The size of foraging parties varied from 2 to 63 individuals and there was evidence that these parties were of ephemoral composition. Mean group size was 13.8 (mode 6-10). Overall, parties comprised males:females:juveniles in the ratio 1:2.6:1.8. It is suggested that variation in the size of foraging parties may be a consequence of the patchy distribution of food trees amongst a forest of inedible Nipa fructicans.
Conservation status of primates in Malaysia, with special reference to Indonesia
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MacKinnon, K., 1987. Conservation status of primates in Malaysia, with
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The distribution of primates and the survey on the aection of forest ®res
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Satellite Remote Sensing of the 1997± 1998 Fires in Indonesia: Data, Methods, and Future Perspectives. WWF-Indonesia On a collection of mammals made in eastern and central Borneo by Mr Carl Lumholtz
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Threats to the proboscis monkey Zoological results of the Dutch Scienti®c Expedi-tion to Central Borneo. The mammals
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A preliminary investigation of the proboscis monkey population in Danau Sentarum Wildlife Reserve
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