Nasalis Larvatus Research Articles

Land cover and Proboscis monkey habitats in Berau Delta, East Kalimantan

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.

Model Assessment on Cooling Effect of Mangrove and Proboscis Monkey Conservation Area in Tarakan City

<p><em>A conservation area for mangrove forests and proboscis monkeys locates within a dense urban centre in Tarakan city. Its surrounding area has rapidly transformed into condensing urban artificial structures with minimal vegetation cover. The study aims to determine the cooling effect of the conservation area toward its surrounding. The study applies model assessment, which comprises ENVI-MET for simulation of air temperature distribution, and Rayman for PMV (Predicted Mean Vote) calculation to investigate the level of heat stress. The result shows that the mangrove cover has a cooling effect effectively after midnight to 11:00 the subsequent day. Specifically, for the surrounding area, it is confined within an 8-hour window (from 0:00 to 8:00). Within this window, inside the mangrove area, ENVI-MET generates significantly lower air temperature, when compared to its surrounding. The mangrove presence correlates to reducing air temperature up to 1.8</em><em>°</em><em> C. The cooling effect also extends to its surrounding with a limited radius (approximately 10 m). However, PMV calculation implies that there is no significant improvement in thermal comfort as a result of the mangrove presence. The results may not adequately reflect the reality in the field. Further research to calibrate PMV measurement that involves human monitoring is required to validate the findings.</em></p>

STRUKTUR POPULASI BEKANTAN (NASALIS LARVATUS) DI RAWA GELAM

Number of proboscis monkey population in Cajuputi Swamp Forest is 258 individual. This population is strongly influenced by condition of its habitat which is to degradation to 3.417 hektar. The object of research is to analyzed structure of proboscis monkey population. Method of research are river survey (Sha et al, 2008) and concentration count (Anonymous, 1981; Alikodra, 2002). The avarage density of proboscis monkey in their homerange is 3 individuals/hectares, with 30,2% males and 48,5 % females. This population is slow growth because there is only one baby/year, this is also indicated by number of 14 individuals babies (5,4%) and 41 infant (15,9%) lower when compared to number of adult indiviuals, so it is very worryng for continued growth of the population.

STASIUN RISET BEKANTAN PADA LAHAN BASAH

Wetlands are a natural habitat for endemic animals of South Kalimantan, namely proboscis monkeys (Nasalis larvatus). These primates are one indicator in wetlands conservation, but now the status of proboscis monkeys is endangered which means wetlands are naturally also damaged. This makes The Indonesian Proboscis Monkey Friends Foundation worried about the preservation of these primates who are endangered in a side the number of foreign researchers who are interested in proboscis monkeys so it also weakens status proboscis monkeys as endemic animals.The Indonesian Proboscis Monkey Friends Foundation wants the proboscis monkey in South Kalimantan to become an identity in the area along with the wetland ecosystem which is the habitat of proboscis monkeys. Therefore a fundamental problem with the design of the Proboscis Monkey Research Station on Wetlands is how the design of the proboscis research station on wetlands is in harmony with natural conditions around it so that it can become the identity of the region. Settlement the problem was solved through the metabolism-organic method and the visual identity-metaphor method. The metabolism-organic method is the solution to the problem of harmony building with nature, while the visual identity-metaphor method is the solution in the matter of regional identity. Based on the two methods, the concept proposed for this design is the concept of "subject-object interaction" which is realized through the concept of "wetland ecology". This concept of "subject-object interaction and wetland ecology" is a concept that elevates interactions between researchers and wetland organisms such as proboscis monkeys by entering the wetland elements into the design of this research station.

STASIUN RISET BEKANTAN PADA LAHAN BASAH

Wetlands are a natural habitat for endemic animals of South Kalimantan, namely proboscis monkeys (Nasalis larvatus). These primates are one indicator in wetlands conservation, but now the status of proboscis monkeys is endangered which means wetlands are naturally also damaged. This makes The Indonesian Proboscis Monkey Friends Foundation worried about the preservation of these primates who are endangered in a side the number of foreign researchers who are interested in proboscis monkeys so it also weakens status proboscis monkeys as endemic animals.The Indonesian Proboscis Monkey Friends Foundation wants the proboscis monkey in South Kalimantan to become an identity in the area along with the wetland ecosystem which is the habitat of proboscis monkeys. Therefore a fundamental problem with the design of the Proboscis Monkey Research Station on Wetlands is how the design of the proboscis research station on wetlands is in harmony with natural conditions around it so that it can become the identity of the region. Settlement the problem was solved through the metabolism-organic method and the visual identity-metaphor method. The metabolism-organic method is the solution to the problem of harmony building with nature, while the visual identity-metaphor method is the solution in the matter of regional identity. Based on the two methods, the concept proposed for this design is the concept of "subject-object interaction" which is realized through the concept of "wetland ecology". This concept of "subject-object interaction and wetland ecology" is a concept that elevates interactions between researchers and wetland organisms such as proboscis monkeys by entering the wetland elements into the design of this research station.

The Validity Handout about Proboscis Monkey (Nasalis larvatus) on Curiak Island as an Enrichment Material for the Concept of Biodiversity in High School

Teaching materials in learning activities have an important meaning so that the learning process is easier and more effective. Local potential can be used as a source of learning to look at phenomena, events, and problems in an area or what is also called contextual learning. The handout is one of the teaching materials that is concise and makes it easier for students to understand learning. The research method used was to analyze the results of research on proboscis monkey (Nasalis larvatus) on Curiak Island by Zainudin and Rezeki, to be used as material for the development of proboscis monkey (Nasalis larvatus) handouts on Curiak Island with the Tessmer development model which was limited to the expert stage review (Expert Test). The validation test was carried out with experts consisting of 3 (three) validators with an overall validity value of 90.6% (very valid and fit for use without revision). Its validity is shown by the average assessment on the feasibility aspect of the content of 85.07% (very valid), the assessment of the feasibility of serving 91.25% (very valid), and the assessment of the language aspect of 87.14% (very valid).Abstrak Bahan ajar pada kegiatan pembelajaran memiliki arti penting, agar proses pembelajaran lebih mudah dan lebih efektif. Potensi lokal dapat dijadikan sumber belajar melihat pada fenomena, peristiwa, maupun permasalahan pada suatu daerah yang disebut dengan pembelajaran kontekstual. Handout merupakan salah satu bahan ajar yang ringkas dan memudahkan peserta didik memahami pembelajaran. Metode penelitian yang digunakan adalah menganalisis hasil penelitian tentang bekantan (Nasalis larvatus) di Pulau Curiak oleh Zainuddin dan Rezeki, untuk dijadikan bahan pengembangan handout bekantan (Nasalis larvatus) di Pulau Curiak dengan model pengembangan Tessmer yang dibatasi hanya pada tahap expert review (Uji Pakar). Uji validasi dilakukan olehn para ahli yang terdiri dari 3 (tiga) validator dengan nilai validitas keseluruhan yaitu 90,6% (sangat valid dan layak digunakan tanpa revisi). Kevalidan ditunjukkan oleh rata-rata penilaian pada aspek kelayakan isi 85,07% (sangat valid), penilaian aspek kelayakan penyajian 91,25% (sangat valid), dan penilaian aspek bahasa 87,14% (sangat valid).

Analysis of fecal nutrients and particle size in captive proboscis monkeys (Nasalis larvatus) fed seasonal dietary foliage at a Japanese zoo.

One male and three female captive proboscis monkeys (Nasalis larvatus) were used as test animals to compare fecal nutrients after being fed seasonal foliage. Foliage and fecal samples were collected during three seasons (spring, summer, and winter). We analyzed crude ash (CA), ether extract (EE), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL). In addition to the above components, for the fecal samples, we examined total fecal nitrogen (TFN), nitrogen in fecal NDF (NDF-N), metabolic fecal nitrogen (MFN), and particle size distribution (MPS). Seasonal differences in foliage components were observed, with NDF and ADF being lowest in spring (p < 0.05). Fecal NDF and ADF also tended to be lowest in spring. Further, the distribution of fecal particle size indicated that MPS tended to increase in winter. The mean fecal NDF content (47.4%) for all three seasons measured in this study was as much as 1.3 times lower than previously reported values in free-ranging specimens. These data provide useful information that can be used to find some suitable food items for the endangered highly folivorous monkeys in captivity.

The Conservation of Proboscis Monkey in Suwi River, East Kalimantan, Indonesia

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

Social and reproductive behaviour of proboscis monkey Nasalis larvatus (van Wurmb, 1787) at Taman Safari Bogor, West Java

Research on social and reproductive behaviours of proboscis monkey Nasalis larvatus (van Wurmb, 1787) at Taman Safari Bogor has been done. The purposes of the research are to evaluate social interactions between male and female proboscis monkeys, between the females, and to evaluate reproductive behaviours in male and female pairs. Observation methods used were scan sampling and ad libitum sampling with fifteen minutes intervals without pause. The observation time was six hours per day and was done for four weeks in November 2019. Subjects observed in the study were one adult male aged 20 years (J) and two adult females aged 14 years (B1) and 11 years (B2) in a glass cage. Social behaviours observed indicate high affiliative behaviours (average 99.28 %) and low aggressive behaviours (average 0.72 %). Reproductive behaviours were carried out by both pairs with the higher frequency of reproductive behaviours happened between J and B1 than J and B2. Based on the t-test carried out with the value of α = 0.05, the frequency of reproductive behaviours of the pairs significantly different with the value of P < 0.05.

The Development of Borneo Wildlife Game Platform

Games are a unique, interesting, and fun entertainment medium. Games can contain education, introduction to certain flora and fauna, work and daily life, intelligence and dexterity. The game built in this study aims to introduce the flora and fauna found in the forests of East Borneo (Kalimantan), Indonesia as the object of a plat former game. Games are built using the Game Development Life Cycle method in order to make good and organized games. The GDLC method contain 6 stages, first is the initiation for the initial idea, second is to preproduction for the asset creation, third stage is production for the system creation, forth is the testing for the trial, fifth is the beta for the external trial, and the sixth stage is to release for publication. The results of the study resulted in the Borneo Wildlife game platform. This game introduces the unique flora and fauna in East Borneo, Indonesia, such as Black Orchids, Ironwood trees, Proboscis monkeys, Mahakam dolphins and Hornbills, as well as how to protect and preserve their nature. The game received 46 downloads from March 1, 2021 to May 24, 2021.

New Insights on the Evolution of the Sweet Taste Receptor of Primates Adapted to Harsh Environments.

Simple SummaryA sense of taste is vital to an animal’s fitness. It enables animals to select and ingest beneficial foods and avoid harmful substances in their daily lives. There have been relatively few studies regarding the evolution of the taste receptor gene for sweetness, particularly in regard to endemic Bornean primates. We constructed TAS1R2 gene phylogenies for 20 anthropoid primate species using four different methods as well as established the phylogenic time divergence. The phylogenetic analysis successfully separated the primates into their taxonomic groups and as per their dietary preferences. Of note, the estimated time of divergence for the primate speciation pattern in this study was more recent than the previously published estimates. This difference may have been due to environmental changes, such as food scarcity and climate change, during the late Miocene epoch, which likely forced primates to adapt their dietary preferences. These findings establish a foundation for further investigations.Taste perception is an essential function that provides valuable dietary and sensory information, which is crucial for the survival of animals. Studies into the evolution of the sweet taste receptor gene (TAS1R2) are scarce, especially for Bornean endemic primates such as Nasalis larvatus (proboscis monkey), Pongo pygmaeus (Bornean orangutan), and Hylobates muelleri (Muller’s Bornean gibbon). Primates are the perfect taxa to study as they are diverse dietary feeders, comprising specialist folivores, frugivores, gummivores, herbivores, and omnivores. We constructed phylogenetic trees of the TAS1R2 gene for 20 species of anthropoid primates using four different methods (neighbor-joining, maximum parsimony, maximum-likelihood, and Bayesian) and also established the time divergence of the phylogeny. The phylogeny successfully separated the primates into their taxonomic groups as well as by their dietary preferences. Of note, the reviewed time of divergence estimation for the primate speciation pattern in this study was more recent than the previously published estimates. It is believed that this difference may be due to environmental changes, such as food scarcity and climate change, during the late Miocene epoch, which forced primates to change their dietary preferences. These findings provide a starting point for further investigation.

KARAKTERISTIKkPOHON TEMPAT TIDUR (night sleeping trees) BEKANTAN (Nasalis larvatus) DI TAMAN WISATA ALAM PULAU BAKUT KABUPATEN BARITO KUALA PROVINSI KALIMANTAN SELATAN

This research was conducted on July 2018 in Pulau Bakut Natural Park, Barito Kuala district, South Kalimantan province. Primates spend more time in sleeping sites, sleeping sites selection can affect their survival. The variables observed in this study were 6 types, namely tree species, tree height and diameter, tree distance from river bank, number of main branches, tree distance from feed sources and number of sleeping trees. Trees used as sleeping trees by proboscis monkeys did not depend on tree species. Sleeping trees were on the edge of the island between 0-15 m from the river. The selected sleeping trees of proboscis monkeys had relatively large stems (between 23.57 to 92.36 cm) and were relatively high (10—35 m) with many branches, overlapped each other, thus created connectivity with the surrounding vegetation. The sleeping trees of proboscis monkeys identified during the study period were 2 (two) species, namely Sonneratia caseolaris (sea rambai/red pidada) and Fagraea crenulata (moon wood). The selection of sleeping trees on the river bank was a proboscis monkey's strategy to avoid predators, avoid parasites from their feces, reduce injuries due to falls, facilitate social interaction and motion efficiencyKeywords: Proboscis monkeys; Nasalis larvatus; night sleeping trees; bakut island

The occurrence of infectious intestinal protozoans in primates of the Lower Kinabatangan floodplain, Sabah, Malaysia (Retracted)

Primate parasite study is an important subject in primate research, especially with the ongoing threats from anthropogenic disturbances such as land conversion and deforestation. This study is conducted to investigate the occurrence of Cryptosporidium and Giardia in primates of the Lower Kinabatangan Wildlife Sanctuary (LKWS), Sabah, Malaysia. Fecal samples collected were tested with immunochromatographic test kits to rapidly screen for Cryptosporidium spp. and Giardia spp. in samples from 45 long-tailed macaques and 40 proboscis monkeys. The overall rate of infection for Cryptosporidium spp. for both species is moderately high at approximately 44.71% (n = 38), with 17.64% (n = 14) individuals are positive with Giardia spp., while 38.82% of the individuals (n=33) tested are not infected with either Cryptosporidium spp. or Giardia spp. Parasite documentation is an integral aspect of primate research, as the information will provide insights on the health status and disease risk of non-human primate populations, thus helping scientists to make better conservation plans for wildlife.

Habitat suitability of Proboscis monkey (Nasalis larvatus) in Berau Delta, East Kalimantan, Indonesia

The proboscis monkey (Nasalis larvatus) is an endemic species to Borneos’ island and is largely confined to mangrove, riverine, and swamp forest. Most of their habitat is outside the conservation due to degraded and habitat converted. Habitat loss is a significant threat to a decreased in the monkey's population. Berau Delta is an unprotected habitat of proboscis monkey, lacking in attention and experiencing a lot of disturbances. This study was conducted on April – August 2019; with aims of the study is to determine Species Distribution Modeling (SDM) for identifying proboscis monkey habitat suitability in Delta Berau, East Kalimantan. The MaxEnt algorithm was used to produce a habitat suitability map based on this species’ occurrence records and environmental predictors. We built the models using 208 points of proboscis monkey presence and 12 environment variables within the study area. Model performance was assessed by examining the area under the curve. The variables most influencing the habitat suitability model were the riverine habitat (60.9%), distance from the pond (16.0%), and distance from the coastline (5.2%). The proboscis monkey suitable habitat is only 9.32% (8,726.58 ha) from 93,631.41 ha total area. The appropriate habitat areas are Sapinang Island, Bungkung Island, Sambuayan Island, Saodang Kecil Island, Besing Island, Lati River, Bebanir Lama, Batu-Batu, and Semanting Bay. We provide some suggestions for the proboscis monkey conservation, which are local protection of uninhabited islands, participatory ecotourism management, and company involvement in protection and management efforts.

Morfologia do tubo digestório de Alouatta belzebul

O Alouatta belzebul é uma espécie classificada como “Vulnerável” e isso se justifica principalmente pela caça, fragmentação e perda do hábitat nas florestas tropicais. A anatomia deste gênero apresenta características peculiares em todas as espécies estudadas, assim este trabalho objetivou descrever a morfologia do tubo digestório de Alouatta belzebul a fim de fornecer subsídios para avaliação de dietas, realização de procedimentos clínicos e cirúrgicos nestes animais. Foram utilizados 10 espécimes de Alouatta belzebul, adultos, machos, de diferentes idade. O trabalho foi realizado na Universidade Federal de Goiás e aprovado no comitê de ética N.083∕17. Os animais previamente criopreservados, foram descongelados e fixados por meio da infusão intramuscular e intracavitária de solução aquosa de folmol a 10%. Existem diversas variações na anatomia macroscópica do tubo digestório entre os primatas e estas variações ocorrem de acordo com os hábitos alimentares. Em Alouatta belzebul, que são folívoros-frugívoros, o tubo digestório abrange a maior parte da cavidade abdominal. Estes animais possuem números variáveis de rugas palatinas, de 10 a 17 pares de rugas, independente do sexo e idade, valores estes diferentes dos relatados para Sapajus libidinosus, de 18 a 21 pares de rugas. O estômago pseudo-compartimentalizado com uma região glandular e duas aglandulares, assemelhando com os achados de Nasalis larvatus. O intestino grosso apresenta o ceco aumentado em formato de L, corroborando com os achados em Callithrix penicillata. Os resultados demonstram que as variações estruturais do tubo digestório ocorrem de acordo com o hábito alimentar das diferentes espécies.

Factors influencing riverine utilization patterns in two sympatric macaques

Many species of terrestrial animals, including primates, live in varied association with the aquatic (e.g., riverine or coastal) environment. However, the benefits that each species receive from the aquatic environment are thought to vary depending on their social and ecological characteristics, and thus, elucidating those benefits to each species is important for understanding the principles of wild animal behaviour. In the present study, to gain a more complete picture of aquatic environment use, including social and ecological factors in primates, factors affecting riverine habitat utilization of two macaque species (Macaca nemestrina and M. fascicularis) were identified and qualitative comparisons were made with sympatric proboscis monkeys (Nasalis larvatus), which have different social and ecological characteristics. Temporal variation in sighting frequency of macaques at the riverbanks was positively related to the fruit availability of a dominant riparian plant species and negatively related to the river water level which affects the extent of predation pressure. Riverine utilization of macaques was greatly influenced by distribution and abundance of food (especially fruit) resources, possibly in association with predation pressure. Additionally, qualitative ecological comparisons with sympatric proboscis monkeys suggest that the drivers of riverine utilization depend on the feeding niches of the species, and different anti-predator strategies resulting from their differing social structures.

Large male proboscis monkeys have larger noses but smaller canines

The uniquely enlarged noses of male proboscis monkeys are prominent adornments, and a sexually selected male trait. A recent study showed significant correlations among nose, body, and testis sizes and clear associations between nose size and the number of females in a male’s harem. However, to date, the analyses of other common male traits, i.e., canines, are lacking. Whereas male nose size had a positive correlation with body size, we unexpectedly found a negative correlation between body and canine sizes. We explain this by an interaction between sexual and natural selection. Larger noses in males may interfere with the use of canines, thereby reducing their effectiveness as weapons. Additionally, longer canines are opposed by natural selection because the larger gape it imposes upon its bearer reduces foraging efficiency, particularly in folivores. This unique case of decoupling of body and canine size reveals that large canines carry an ecological cost.

Effects of amusing memes on concern for unappealing species.

There is limited knowledge of the mechanisms that can inspire people's concern and engagement in the protection of unpopular and unappealing species. We analyzed Polish people's interest in themed internet memes featuring the proboscis monkey (Nasalis larvatus) and the consequences of this interest for conservation marketing. We examined Google Trends data, used Google Search, and searched popular media materials to estimate interest in the proboscis monkey in Poland. Photos of the proboscis monkey when presented with humor in internet memes attracted as much interest as usually more popular species (e.g., koala, panda, and orangutan) used in marketing by nongovernmental organizations. Amusing internet memes spread by social media positively correlated with increasing interest in the unappealing species, such as proboscis monkey. Interest in amusing internet memes positively correlated with individuals' decisions to donate to 6 crowdfunding actions. Thus, conservation marketing that includes amusing memes and social media may provide a worthwhile complement to traditional campaigns and are likely to influence individuals who are unaffected by the usual means.

Emerging challenges for sustainable development and forest conservation in Sarawak, Borneo.

The forests of Borneo—the third largest island on the planet—sustain some of the highest biodiversity and carbon storage in the world. The forests also provide vital ecosystem services and livelihood support for millions of people in the region, including many indigenous communities. The Pan-Borneo Highway and several hydroelectric dams are planned or already under construction in Sarawak, a Malaysian state comprising part of the Borneo. This development seeks to enhance economic growth and regional connectivity, support community access to services, and promote industrial development. However, the implications of the development of highway and dams for forest integrity, biodiversity and ecosystem services remained largely unreported. We assessed these development projects using fine-scale biophysical and environmental data and found several environmental and socioeconomic risks associated with the projects. The highway and hydroelectric dam projects will impact 32 protected areas including numerous key habitats of threatened species such as the proboscis monkey (Nasalis larvatus), Sarawak surili (Presbytis chrysomelas), Bornean orangutans (Pongo pygmaeus) and tufted ground squirrel (Rheithrosciurus macrotis). Under its slated development trajectory, the local and trans-national forest connectivity between Malaysian Borneo and Indonesian Borneo would also be substantially diminished. Nearly ~161 km of the Pan-Borneo Highway in Sarawak will traverse forested landscapes and ~55 km will traverse carbon-rich peatlands. The 13 hydroelectric dam projects will collectively impact ~1.7 million ha of forest in Sarawak. The consequences of planned highway and hydroelectric dams construction will increase the carbon footprint of development in the region. Moreover, many new road segments and hydroelectric dams would be built on steep slopes in high-rainfall zones and forested areas, increasing both construction and ongoing maintenance costs. The projects would also alter livelihood activities of downstream communities, risking their long-term sustainability. Overall, our findings identify major economic, social and environmental risks for several planned road segments in Sarawak—such as those between Telok Melano and Kuching; Sibu and Bintulu; and in the Lambir, Limbang and Lawas regions—and dam projects—such as Tutoh, Limbang, Lawas, Baram, Linau, Ulu Air and Baleh dams. Such projects need to be reviewed to ensure they reflect Borneo’s unique environmental and forest ecosystem values, the aspirations of local communities and long-term sustainability of the projects rather than being assessed solely on their short-term economic returns.

Stability Analysis on Mangrove Forest Resource Models with Proboscis Monkey and Fish Pond Land Interaction with Time Delay

Mangrove is one of the most important ecosystems in Balikpapan, where the Proboscis monkeys-an endemic animal in Borneo-lives. The growth of their population is affected by the opening of pond land by human around the forest. In this research, the problem from the interaction among the growth rate of mangrove, monkey and the opened pond land is presented in a mathematics model in the form of prey-predator for those three variables. We give an attention to the model by introducing time delays for the growth rate of fish pond land. It shows that the linearized system performs a small perturbation and the value of critical delay of the characteristic equation will affects the stability of the equilibrium point and causes stability changes (Hopf bifurcation). In this work, we obtain the existence of a critical value of the time delay and the fulfillment of the transversal conditions.