First Estimates of Primate Density and Abundance in Siberut National Park, Mentawai Islands, Indonesia

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Short Communication First estimates of primate density and abundance in Siberut National Park, Mentawai Islands, Indonesia

M ARCEL C. QUINTEN,FIFIN N OPIANSYAH and J . K EITH H ODGES

Abstract In  we carried out the first systematic survey to the IUCN Red List (IUCN, ). The pig-tailed langur is determine the density and abundance of endemic forest pri- among the  most threatened primates (Mittermeier mates in Siberut National Park, in the Mentawai Islands of et al., ). West Sumatra, Indonesia. Distance sampling was employed Regardless of their conservation status, there is a dearth to survey  transects located systematically throughout the of reliable information on the size of the region’s primate Park, yielding a total survey effort of  km and  obser- population, which is essential for effective management vations of primates for data analysis. From density estimates and conservation planning. The few publications that have for the four resident primate species, the Siberut langur presented population estimates for the Mentawai Islands are Presbytis siberu, the pig-tailed snub-nosed langur Simias typically species-specific (e.g. Tilson, ; Whittaker, ) concolor, Kloss’s gibbon Hylobates klossii and the Siberut and/or base their estimates on geographically restricted data macaque Macaca siberu, we extrapolated a total population (e.g. Waltert et al., ; Quinten et al., ). Significantly, of c. , primates within the Park. We conclude that there is a lack of data from the archipelago’s only protected Siberut National Park is of major significance for the contin- area, Siberut National Park, located on the largest and ued survival of Siberut’s endemic primates, and provide re- northernmost of the four islands. Formally declared in commendations to help ensure that it will continue to , the Park covers .% of Siberut (Fig. ) and comprises function as a refuge for primates. predominantly evergreen primary lowland rainforest (.%; M. Quinten, unpubl. data). Unlike many of Keywords Hylobates klossii, line-transect survey, Macaca Indonesia’s protected areas, Siberut National Park was de- siberu, Mentawai Islands, population density, Presbytis si- signed to contain human settlements. It is subdivided into beru, Siberut National Park, Simias concolor three land-use zones (sanctuary, traditional use and park village) and there are at least , inhabitants in the park  he Mentawai Island primates are a unique community village zone (PHPA, ), which is the least restricted. As Tof sympatrically occurring, endemic species of the with many government-established parks and reserves, pro-  c. , km (BPS, ) Mentawai Archipelago in West tection and enforcement within the Park are hampered by ’ Sumatra, Indonesia. On the four main islands (Siberut, staff members lack of knowledge and training in wildlife Sipora, North Pagai and South Pagai) six species (Roos ecology and conservation management, and by insufficient . et al., ) coexist: the Siberut macaque Macaca siberu, funding. Thus, despite its -year history and its potential the Pagai Island macaque Macaca pagensis, the Siberut lan- importance as a refuge for primates, no systematic surveys gur Presbytis siberu, the Pagai langur Presbytis potenziani, have been carried out within the Park boundaries and the pig-tailed snub-nosed langur Simias concolor, and consequently no data on primate density and abundance Kloss’s gibbon Hylobates klossii. Threatened mainly by are available. anthropogenic hunting and habitat loss (commercial log- Following on from surveys of primates in the north of the  ging, agriculture), all six species are considered to be in de- island, outside the National Park (Waltert et al., ;  cline (Whittaker, ). They are categorized as Vulnerable Quinten et al., ), the Siberut Conservation (M. siberu), Endangered (P. siberu (as P. potenziani siberu) Programme established a collaboration with the Siberut and H. klossii) or Critically Endangered (P. potenziani (as National Park Authority, Green Siberut Association, and P. potenziani potenziani), M. pagensis and S. concolor)on UNESCO to carry out surveys within the Park. Our aims were to provide the first systematic and reliable estimates of primate density and abundance in the Park, extend the

MARCEL C. QUINTEN (Corresponding author) and J. KEITH HODGES Reproductive existing dataset on primate population sizes in the Biology Unit, German Primate Center, Kellnerweg 4, Goettingen 37077, Mentawai Islands, and provide training in primate survey Germany, and Siberut Conservation Programme, Pola Mas, Padang 25122, methodology and data analysis for staff of the National Indonesia. E-mail [email protected] Park Authority and affiliated organizations in the region. FIFIN NOPIANSYAH Siberut National Park Office, Padang, West Sumatra,  −  Indonesia We organized a -day workshop ( May ), during which participants received in-depth training in theor- Received  August . Revision requested  November . Accepted  December . First published online  March . etical (e.g. survey design, general methodology) and

Oryx, 2016, 50(2), 364–367 © 2015 Fauna & Flora International doi:10.1017/S0030605314001185 Downloaded from https://www.cambridge.org/core. IP address: 170.106.40.139, on 28 Sep 2021 at 00:15:08, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605314001185 Primates in Siberut National Park 365

primate observations by transect, and analysed each species separately using both visual and acoustic observations. We truncated the data to estimate the detection function g(x) and the cluster (group) size (Table ); we determined cluster size using the size bias regression method, regressing ln(cluster size) against the estimated g(x). By surveying all  transects – times we achieved a total survey effort of  km, yielding  detection events for the four primate species on Siberut (Table ): S. concolor (), M. siberu (), P. siberu () and H. klossii (). Presbytis siberu was the most abundant primate, and based on a density   of c. . individuals per km (c. . clusters per km )we estimate the total population in the Park to be , indi-  viduals. We modelled a density of . individuals per km  (c. . clusters per km ) and a total population of c. , individuals for Siberut’s other colobine, S. concolor. The estimated densities of H. klossii and M. siberu were . and   . individuals per km (c. . and c. . clusters per km ), respectively, yielding population estimates of c. , gib- bons and , macaques (Table ). Collectively, this indicates a population of c. , primates within the Park. However, as our survey transects were located almost ex- clusively in primate habitat (e.g. primary and swamp forest), leaving non-suitable habitat underrepresented (c. –%of the Park area, including bare land and agricultural areas; M. Quinten, unpubl. data), this number may represent a slight overestimation. FIG. 1 Locations of  closed-circuit transects, within a Given that no other systematic survey of primates has systematic-random sampling grid, used to survey the four been conducted in Siberut National Park we cannot com- endemic primate species in Siberut National Park in the pare our results with earlier information, or comment on Mentawai Islands, Indonesia. The rectangle on the inset indicates population changes over time. A comparison with the the location of the main map in Indonesia. only available population estimates for the whole island (Whittaker, , largely based on WWF, ; Table ), practical (e.g. equipment handling, transect cutting) aspects however, suggests that a substantial proportion of the popu- of primate population surveys. We then assigned successful lations of all four primate species occurs within the Park, participants to one of seven teams and sent them to the field emphasizing its conservation importance for the region’s to conduct distance sampling surveys (Buckland et al., , primates. It also indicates that P. siberu and S. concolor are ) of primates at two or three of a total of  closed- considerably more abundant on Siberut than Whittaker circuit transects (length per transect , m), located ac- () suggested (our estimates for the Park are c. .– cording to a random vector grid (Fig. ). The survey design times higher than those of Whittaker for the entire island). represented the best possible solution taking into account Given the Park’s comparatively high abundance of pri- logistical difficulties (no roads, remoteness, difficult terrain) mates, and considering that () the Park covers almost and available resources (time, manpower, budget). half of Siberut Island, () the areas outside the Park are lar- All teams conducted daily survey walks during times of gely production and conversion forest, and () there is little peak primate activity (c. .–. and .–.), and remaining forest (and thus primate habitat) on the three recorded standard survey data (cf. Quinten et al., ). southern Mentawai Islands, we conclude that Siberut Using a laser range finder, perpendicular distances were National Park represents the most important habitat for pri- measured from the transect line to the centre of all counta- mates in the Mentawai region. To successfully fulfil its func- ble individuals of each primate cluster; when primates were tion as a refuge, the Park administration will need to address detected acoustically the perpendicular distance to the esti- two main challenges. Firstly, encroachment associated with mated location was measured. All teams returned to main- human population growth (cf. PHPA, ) continues to land Sumatra in June  to attend a workshop, where we have a negative impact on primate populations in the analysed all data using DISTANCE v. . (Thomas et al., Park, principally in terms of habitat loss and hunting ). For this purpose we pooled individual surveys and (Quinten et al., ). Secondly, inadequate funding and

TABLE 1 Species-specific survey results for the primates inhabiting Siberut National Park, Indonesia (Fig. ), and previous estimates for Siberut Island as a whole (Whittaker, ), with the analysis parameters, mean encounter rate, size and density of primate clusters, detection probability, mean density estimate for individuals, and estimated population. 170.106.40.139 Pig-tailed langur Siberut macaque Mentawai langur Kloss’s gibbon Simias concolor Macaca siberu Presbytis siberu Hylobates klossii Analysis parameters

, on * c (m) 50 62 60 56 28 Sep2021 at00:15:08 w (m) 115 94 100 93 nt 52 79 95 59 Oryx na 48 43 77 49 06 02,364 50(2), 2016, , nvisual/acoustic 45/3 32/11 62/15 41/8 Analysis results − Mean encounter rate for clusters, km 1 (95% CI) 0.25 (0.17–0.38) 0.22 (0.13–0.39) 0.40 (0.28–0.57) 0.26 (0.17–0.39) , subjectto theCambridgeCore termsofuse,available at Mean cluster size (95% CI) 3.0 (2.4–3.8) 3.2 (2.2–4.6) 2.4 (2.0–2.8) 2.7 (2.1–3.4) −2 – – – – –

367 Mean cluster density, km (95% CI) 2.8 (1.3 4.6) 1.8 (1.0 3.2) 4.4 (2.9 6.8) 2.4 (1.5 3.8) Detection probability (95% CI) 0.38 (0.28–0.51) 0.68 (0.52–0.89) 0.46 (0.34–0.61) 0.58 (0.45–0.74) © −2 05Fua&FoaItrainldoi:10.1017/S0030605314001185 International Flora & Fauna 2015 Mean density, individuals km (95% CI, CV) 8.5 (5.0–14.5, 27.2) 5.6 (2.8–11.1, 35.2) 10.4 (6.6–16.5, 23.1) 6.3 (3.7–10.6, 26.5) Estimated population size (range), Siberut National Park 14,112 (8,252–24,133) 9,248 (4,639–18,438) 17,384 (11,014–27,439) 10,484 (6,206–17,713) Results of Whittaker (2005) Estimated population size (range), Siberut Island 10,750 (6,000–15,500) 23,500 (17,000–30,000) 5,550 (1,600–9,500) 19,500 (18,000–21,000)

*c, truncation distance for cluster size estimation; w, truncation distance for density estimation; nt, total number of observed clusters; na, number of clusters used for data analysis after truncation; nvisual/acoustic , ratio of visual versus acoustic observations Primates in Siberut National Park 367

levels of training in wildlife management, together with a BUCKLAND, S.T., PLUMPTRE, A.J., THOMAS,L.&REXSTAD, E.A. fragile relationship between the Park authorities and some () Design and analysis of line transect surveys for primates.  – of its resident communities, compromise the effectiveness International Journal of Primatology, , . IUCN () IUCN Red List of Threatened Species v. .. Http:// of the Park in achieving its conservation objectives. www.iucnredlist.org [accessed  August ]. We advise the Indonesian Ministry of Forestry to in- MITTERMEIER, R.A., SCHWITZER, C., RYLANDS, A.B., TAYLOR, L.A., crease funding for the Park, to ensure adequate human re- CHIOZZA, F., WILLIAMSON, E.A. et al. (eds) () Primates in Peril: sources to support the enforcement of its statutes on a local The World’s  Most Endangered Primates –. IUCN/SSC level and to improve staff training in conservation manage- Primate Specialist Group, International Primatological Society, Conservation International & Bristol Conservation and Science ment. Greater emphasis needs to be placed on outreach ac- Foundation, Bristol, UK. tivities to foster closer interaction and cooperation between PHPA () Siberut National Park Integrated Conservation and Park management and the resident communities, raising Development Management Plan (–). Volume I: Current local awareness of the value of Siberut’s rainforest habitat Conditions and Evaluation. Chemonics International in association and the importance of a sustainable approach to resource with PT. Indeco Duta Utama and PT. Nadya Karsa Amerta, for Ditjen Perlindungan Hutan dan Pelestarian Alam, Departemen utilization. Finally, we recommend that further research Kehutanan, Jakarta, Indonesia.  be carried out, specifically ( ) studies to examine the socio- QUINTEN, M.C., STIRLING, F., SCHWARZE, S., DINATA,Y.&HODGES, economic needs of the Park’s inhabitants, and assess their J.K. () Knowledge, attitudes and practices of local people on impact on the land, () time-series land-cover assessments Siberut Island (West-Sumatra, Indonesia) towards primate hunting  – to determine rates of deforestation/habitat loss, and () and conservation. Journal of Threatened Taxa, , . QUINTEN, M.C., WALTERT, M., SYAMSURI,F.&HODGES, J.K. () long-term monitoring of population trends in the Park – Peat swamp forest supports high primate densities on Siberut Island, (with surveys every years); ideally this would be comple- Sumatra, Indonesia. Oryx, , –. mented by surveys outside the Park in Siberut’s production ROOS, C., BOONRATANA, R., SUPRIATNA, J., FELLOWES, J.R., GROVES, forest/timber concessions. C.P., NASH, S.D. et al. () An updated taxonomy and conservation status review of Asian primates. Asian Primates Journal, , –. Acknowledgements THOMAS, L., LAAKE, J.L., REXSTAD, E., STRINDBERG, S., MARQUES,F. F.C., BUCKLAND, S.T. et al. () Distance .. Release . Research We thank all partners (the Siberut National Park Authority, Unit for Wildlife Population Assessment, University of St. Andrews, the Siberut Conservation Programme, Green Siberut St. Andrews, UK. Http://www.ruwpa.st-and.ac.uk/distance/ [accessed  August ]. Association, and UNESCO) for their invaluable efforts in TILSON, R.L. () Social organization of Simakobu monkeys (Nasalis planning, coordinating and funding the project, specifically concolor) in Siberut Island, Indonesia. Journal of Mammalogy, , Mr Jusman, Ms Pio, Ms Acha De La Presa and Dr –. Matthias Waltert. We thank the Rufford Foundation, the WALTERT, M., ABEGG, C., ZIEGLER, T., HADI, S., PRIATA,D.& Mohamed bin Zayed Species Conservation Fund and the HODGES, J.K. () Abundance and community structure of Spanish Agency for International Cooperation for financial Mentawai primates in the Peleonan forest, north Siberut, Indonesia. Oryx, , –. support, and the Indonesian Institute of Sciences for provid- WHITTAKER, D.J. () New population estimates for the endemic ing the necessary research permits. Finally, we thank the Kloss’s gibbon (Hylobates klossii) on the Mentawai Islands, members of the dedicated survey teams who made this Indonesia. Oryx, , –. project possible, including the National Park employees WHITTAKER, D.J. () A conservation action plan for the Mentawai  – Ridho, Dedet, Kusmiadi, Efrinaldi, Matheus and Badul, primates. Primate Conservation, , . WWF () Saving Siberut: A Conservation Master Plan. WWF the Green Siberut Association staff Yoyok and Silvanus, Indonesia Programme, Bogor, Indonesia. the SMILE-team Fabianus, Ronal and Hamdi, Bogor Agricultural University students Dani and Yandhi, Darmanto from UNESCO, and Siswanto from R&D Forestry. Biographical sketches

References M ARCEL C. QUINTEN is a conservation biologist working with the German Primate Center and the Siberut Conservation Programme BPS (BADAN PUSAT STATISTIK)() Kepulauan Mentawai in on the preservation of the endemic primates of the Mentawai Figures . Badan Pusat Statistik Kabupaten Kepulauan Mentawai, Archipelago. F IFIN N OPIANSYAH is a conservation analyst for the Tuapejat, Sumatra, Indonesia. Siberut National Park Authority and is conducting doctoral research BUCKLAND, S.T., ANDERSON, D.R., BURNHAM, K.P., LAAKE, J.L., on protected area management at Bogor Agricultural University in BORCHERS, D.L. & THOMAS,L.() Introduction to Distance Java, Indonesia. J. K EITH H ODGES has research interests in evol- Sampling: Estimating Abundance of Biological Populations. Oxford utionary endocrinology and comparative reproduction in primates, University Press, Oxford, UK. and primate conservation.