BIODIVERSITAS ISSN: 1412-033X Volume 21, Number 11, November 2020 E-ISSN: 2085-4722 Pages: 5155-5163 DOI: 10.13057/biodiv/d211121 Habitat suitability of Proboscis monkey (Nasalis larvatus) in Berau Delta, East Kalimantan, Indonesia TRI ATMOKO1,2,♥, ANI MARDIASTUTI3♥♥, M. BISMARK4, LILIK BUDI PRASETYO3, ♥♥♥, ENTANG ISKANDAR5, ♥♥♥♥ 1Research and Development Institute for Natural Resources Conservation Technology. Jl. Soekarno-Hatta Km 38, Samboja, Samarinda 75271, East Kalimantan, Indonesia. Tel.: +62-542-7217663, Fax.: +62-542-7217665, ♥email: [email protected], [email protected]. 2Program of Primatology, Institut Pertanian Bogor. Jl. Lodaya II No. 5, Bogor 16151, West Java, Indonesia 3Department of Forest Resource Conservation and Ecotourism, Faculty of Forestry and Environment, Institut Pertanian Bogor. Jl. Lingkar Akademik, Kampus IPB Dramaga, Bogor16680, West Java, Indonesia. Tel.: +62-251-8621677, ♥♥email: [email protected], ♥♥♥[email protected] 4Forest Research and Development Center. Jl. Gunung Batu No 5, Bogor 16118, West Java, Indonesia 5Primate Research Center, Institut Pertanian Bogor. Jl. Lodaya II No. 5, Bogor 16151, West Java, Indonesia. Tel./fax.: +62-251-8320417, ♥♥♥♥email: [email protected] Manuscript received: 1 October 2020. Revision accepted: 13 October 2020. Abstract. Atmoko T, Mardiastuti A, Bismark M, Prasetyo LB, Iskandar E. 2020. Habitat suitability of Proboscis Monkey (Nasalis larvatus) in Berau Delta, East Kalimantan, Indonesia. Biodiversitas 21: 5155-5163. Habitat suitability of Proboscis monkey (Nasalis larvatus) in Berau Delta, East Kalimantan, Indonesia. The proboscis monkey (Nasalis larvatus) is an endemic species to Borneo's island and is largely confined to mangrove, riverine, and swamp forests. Most of their habitat is outside the conservation due to degraded and habitat converted. Habitat loss is a significant threat to decrease in 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 during April - August 2019; with the aims of identifying proboscis monkey habitat suitability in Delta Berau, East Kalimantan through Species Distribution Modeling (SDM). For SDM, 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 was predicted to be only 9.32% (8,726.58 ha) out of total 93,631.41 ha area. The appropriate habitat areas determined were Sapinang Island, Bungkung Island, Sambuayan Island, Saodang Kecil Island, Besing Island, Lati River, Bebanir Lama, Batu-Batu, and Semanting Bay. This study also provides some suggestions for conservation of proboscis monkey, which include local protection of uninhabited islands, participatory ecotourism management, and company involvement in protection and management efforts. Keywords: Colobinae, Species Distribution Model, MaxEnt, primate conservation, riverine forest Abbreviations: SDM: Species Distribution Model, MaxEnt: Maximum Entropy, VIF: variance inflation factor, FCD: Forest Canopy Density, ROC: Receiver Operating Characteristic, AUC: Area Under the Curve, ULUP: Urban Land-Use Plan. INTRODUCTION cultivation, palm oil plantation (Soendjoto and Nazaruddin 2012), tourist facilities (Boonratana 2013), coal loading Proboscis monkey (Nasalis larvatus Wurmb.) is a area and haul route (Atmoko et al. 2012). The proboscis unique primate species of old world monkey that belongs monkey habitat has been lost more than 45% of the initial to the Colobinae subfamily. Endangered species status habitat of 121,670 km2 (Meijaard and Nijman 2000), with a A2cd was confirmed by the red list IUCN committee since destruction rate is estimated at 2% per year (Manansang et 2000 (Boonratana et al. 2020) and included in Appendix I al. 2005), and only 9% of them currently remains in of CITES (www.cites.org). The monkeys are protected and protected areas (Wardatutthoyyibah et al. 2019). This highly prioritized for conservation by Indonesian law. condition has caused the population to decrease by more However, the monkey population is decreasing due to than 70% in the past 36 years (Boonratana et al. 2020). destruction and loss of their primary habitat in mangrove The proboscis monkey is an endemic primate for and riverine forest by various human activities. Since Borneo and small islands nearby in the vicinity. mangrove forests have enormous potential for fish and Distribution of animals covered in three countries, shrimp pond fisheries, therefore many mangrove forests are Indonesia (all province of Kalimantan), Malaysia (Sabah, being converted into ponds (Atmoko 2015). Likewise, Sarawak), and Brunei Darussalam, which is the largest riparian forests and rivers have mainly been used for population found in the Kalimantan region (Phillips and transportation to Kalimantan's deep inland for a long time Phillips 2016). Delta Berau is the crucial habitat of ago. Frequent river access is causing riverine forests to proboscis monkey in East Kalimantan with a large quickly degrade to other land use, such as settlements, population (Atmoko et al. in press). Any aspect of study 5156 BIODIVERSI TAS 21 (11): 5155-5163, November 2020 related to proboscis monkey in this location has never been roxellana (Dong 2019), Hylobates moloch (Widyastuti et done. Information on the distribution and habitat suitability al. 2020), Semnopithecus entellus (Chetan et al. 2014) is the primary data needed to carry out conservation efforts. and Trachypithecus geei (Thinley et al. 2019). So far, Geographic information systems (GIS) have been MaxEnt spatial modeling of the distribution of proboscis applied widely in the distribution of wildlife modeling monkeys has been carried out by (Wardatutthoyyibah et al. through the Species Distribution Model (SDM) approach 2019) for the whole of Kalimantan. Whereas in this study, (Prasetyo 2017). Several methods used for SDM techniques the focus will be on the specific area in the Berau Delta, with the presence-absence dataset are generalized linear East Kalimantan. This study aims to develop the model of models (GLMs) and generalized additive models (GAMs) relationships between the existence of the proboscis (Guisan et al. 2002), whereas BIOCLIM (Booth 2018), monkey on the biological components habitat, disturbance DOMAIN (Sarquis et al. 2018) and maximum entropy from human activity, and climatic or environment (MaxEnt) (Phillips et al. 2006) use presence data only. The variables. The habitat suitability model resulting would be MaxEnt is a most popular tool with excellent performance useful for the proboscis monkeys conservation planning at compared with other SDM methods (Merow et al. 2013), the landscape scale. which is through an algorithm equation that estimates the probability distribution for a species occurrence based on environmental variables. MATERIALS AND METHODS MaxEnt has been used to predict the distribution of primate animals, such as Gorilla beringii beringei (Thorne Study area et al. 2013), Pan troglodytes (Fitzgerald et al. 2018), The study was conducted in the Berau Delta, Berau Alouatta ululata (Filho and Palmeirim 2019), Pongo District, East Kalimantan, Indonesia, between 2o17’-1o50’ tapanuliensis (Rahman et al. 2019), Pygathrix N and 117o31’-118o01’ E (Figure 1). nemaeus (Tuan Anh et al. 2019), Rhinopithecus Figure 1. The study site in Berau Delta, East Kalimantan, Indonesia ATMOKO et al. – Habitat suitability of Proboscis monkey in Berau Delta, Indonesia 5157 In the study area Proboscis monkey's habitat is conducted on large and selected small rivers along 413.96 restricted to the rivers banks and shores. Therefore the km stretch. To get an accurate geographic point, the study area bordered from rivers and beaches as far as 1,810 positions of monkeys were recorded using "sight 'n go" m. That distance is the furthest distance of the daily range facility on GPS Garmin CSx60, whose accuracy was of proboscis monkey (Boonratana 2000). The total study further increased by putting the direction and distance of area after it was bordered was 936.31 km2. The area’s the animals from the observer calculated from laser annual precipitation in 2019 reached 1,727 mm, mean distance meter. Duplicate data records on the single grid temperature varied between 23°C and 33°C, and mean cell (30 m x 30 m) were removed, to reduce spatial bias relative humidity was 84.9% (www.bmkg.go.id). The Delta (Dong 2019) and the occurrence coordinates were tabulated Berau is flat with an altitudinal range from 0 to 290 m in a comma-separated value (CSV) format. above sea level (asl) and the highest peak at Padai Hill. The forest type within the area is riverine and mangrove forests. Habitat variables The mangrove forest is dominated by This study used 12 explanatory variables categorized Rhizophora mucronata, R. apiculata, Bruguiera sp., from biology, disturbance, and physico-environmental Sonneratia alba and Avicennia alba, whereas the riverine variables (Table 1). We used biological factors represented forest is dominated by Sonneratia caseolaris, Vitex pinnata, by Forest Canopy