OuTrop: Gibbon Density Comparison

Ex- Gibbon Density and Comparison with Other Areas

August 2011

The Tropical Peatland Project

Protecting ’s biodiversity since 1999

outrop.com | facebook.com/outrop | @outrop

www.outrop.com @outrop facebook.com/outrop OuTrop: Gibbon Density Comparison

The Orangutan Tropical Peatland Project is an -based research and conservation organisation that works in partnership with the Centre for International Cooperation in Sustainable Management of Tropical Peatlands (CIMTROP) at the University of . We are supported by the Orangutan Tropical Peatland Trust (registered UK Charity no.1142870), and linked to the Wildlife Conservation Unit (WildCRU) at the Univer- sity of Oxford, the Wildlife Research Group in the Anatomy School of the University of Cambridge, the College of Life and Environmental Sciences at the University of Exeter, and the Department of Geography at the University of Leicester.

Suggested citation: Cheyne SM (2011). Ex-Mega Rice Project Gibbon Density and Comparison with other Sites. In Orangutan Tropical Peatland Project Report. Palangka Raya: Orangutan Tropical Peatland Project. © 2011, The Orangutan Tropical Peatland Project. All rights reserved. [email protected] : www.outrop.com : www.outrop.blogspot.com Cover photo: Andrew Walmsley/OuTrop

www.outrop.com @outrop facebook.com/outrop OuTrop: Gibbon Density Comparison

Contents

Introduction 1

Methods 2

Results 3

Discussion and conservation importance of MRP area 4

References 6

www.outrop.com @outrop facebook.com/outrop OuTrop: Gibbon Density Comparison

Introduction

The Mega Rice Project in Central , Indonesia was initiated in 1996 with the goal of clear-felling one million hectares of unproductive and sparsely populated lowland peat-swamp forest into rice paddies in an attempt to alleviate Indonesia’s growing food shortage (Boehm and Siegert, 1999). The Indonesian government made a large investment in constructing an estimated 4,600 kilometres of drainage canals, the largest of them 30 metres wide irrigation canals and removing trees, but the project did not succeed because rice could not be cultivated in the acidic soil. It was eventually abandoned after causing extensive damage to the forest and peat (Aldhous, 2004).

The former Mega Rice Project is part of a stretch of forested peatland that covers a large extent of the lowland river plains of southern Borneo. Although the area was once connected, it is now highly fragmented. The study area for this work is Block C, one of the five blocks A-E that comprise the entire ex-Mega Rice Project. It is surrounded by the to the east, the Sabangau River to the west, the to the south, and the main Palangka Raya-Sampit road to the north. Block C and the adjacent Sabangau Forest make up the Sabangau basin and are divided by the black water Sabangau River.

www.outrop.com @outrop facebook.com/outrop 1 OuTrop: Gibbon Density Comparison

Methods

Gibbon density was estimated using fixed-point counts, as described by Brockelman and Ali (1987), at three distinct survey sites within the research area. This method has been rec- ommended for the survey of gibbons for the following reasons: first, because the gibbons’ inconspicuous behavior and preference for high canopy makes the use of line transects for surveying unsuccessful [Brockelman and Ali 1987; Brockelman and Srikosamatara 1993; O’Brien et al. 2004; Nijman and Menken 2005; Cheyne et al. 2007; Hamard et al. 2010]. Sec- ondly, because the territorial behaviour of gibbons allows efficient mapping of triangulated points (Sutherland, 2000). The animals’ loud calls, audible from a considerable distance, allow their detection from greater distances than by using sightings [Davies 2002]. Finally, fixed-point counts allow quick, time-efficient surveys, with more reliable results than a line transect survey conducted within the same time frame (Nijman and Menken, 2005).

The density estimates were obtained with the following formula, developed by Brockelman and Ali (1987): D = n / [p(m) x E], where n is the number of groups heard in an area as deter- mined by the mapping, p(m) is the estimated proportion of groups expected to sing during a sample period of m days, and E is the effective listening area [Brockelman and Ali 1987; Nij- man and Menken 2005; Cheyne et al. 2007]. The correction factor p(m) was determined at each site with the formula p(m) = 1 – [1- p(1)]m, with p(1) being the singing probability for any given day, and m being the number of survey days. The effective listening area was cal- culated for each site using a fixed radius of 1km around each listening post, and was defined by the area in which at least two of the listening posts could hear gibbons singing.

Figure 1: Map of Sabangau catchment. Main field site in Sabangau (LAHG) = blue circle, Mega Rice field site = yellow circle. Dark green is remaining forest.

www.outrop.com @outrop facebook.com/outrop 2 OuTrop Standard Operating Procedure:OuTrop: Gibbon Litter-fall Density Comparison

Figure 2: Google Earth image of Sabangau catchment. Main field site in Sabangau (LAHG) = blue circle, Mega Rice field site = yellow circle. Results

Table 1: Basic data on survey carried out from 4-7 August 2011 Individuals in ELA based Days of survey Width of buffer (km) Calling probability (p(m)) Effective Listening Area Total study groups in ELA on groups heard (assume (ELA) (km2) 3.5 gibbons/group based on sightings)

4 1 0.6 6.44 9 31.5

www.outrop.com @outrop facebook.com/outrop 3 OuTrop: Gibbon Density Comparison

Table 2: Results of density and population - Kalampangan

Groups/km2 (D=n/[p(m) Individuals/km2 Lone gibbons/km2 Total gibbons/km2 x E)

2.33 4.89 1 5.89

Total population estimate for 1254 2km [Cattau 2010}: 7385 individuals

Individuals/km2 based on groups heard (assuming 3.5 gibbons/group from sightings [Cheyne et al. 2007]) Lone gibbons (5.5% of paired population [Cowlishaw 1996; Cheyne et al. 2007]) Discussion and conservation importance of MRP area

H. albibarbis is listed as Endangered on the IUCN Red List 2008 [IUCN 2008] based on an estimated population reduction of over 50% when considering the past 30 years and projected future habitat change due to draining of peat-swamps, logging and burning into the next 15 years (totalling 45 years which is approximately 3 generations). Where the species persists there is hunting and collection for the wildlife trade. A large part of the species range is in peat-swamp – an extremely threatened ecosystem. This species may qualify for Critically Endangered in the future if rates of habitat change increase, and thus should be carefully monitored as availability of suitable habitat and population are declining.

There is a severe lack of data on non-protected areas or small forest areas which may contain viable populations. In the absence of a full Population and Habitat Viability Analysis (PHVA) all survey data are vitally important to obtain accurate population estimates of this species. Based on these data, this area is home to 3% of the global population of this endangered species. Thus, this area is clearly capable of supporting a viable population but it is isolated from other potential corridors of genetic transfer from other forests and the area is highly fragmented.

www.outrop.com @outrop facebook.com/outrop 4 OuTrop: Gibbon Density Comparison

Figure 3 showing average density for Sabangau of 2.6 groups/km2 (green circle) and for MRP 2.33 groups/ km2 (red circle).

Burnt area separating forest fragments View of remaining forest

Based on these results the density of gibbons is less than that in Sabangau (2.6 groups/km2) as is the number of gibbons/km2 (5.89 compared to 10.7 for Sabangau). The estimate of ±7,000 gibbons indicates that this forest could support a viable population of gibbons, despite the highly fragmented and disturbed state of the forest and surrounding areas. These are preliminary data based on only 4 days of survey and based on these data it is clear that more survey work is needed. It is clear that without extensive attempts to connect the fragments, this population of gibbons does not have a long-term future.

www.outrop.com @outrop facebook.com/outrop 5 OuTrop: Gibbon Density Comparison

References

Aldhous, P. 2004. Land remediation: Borneo is burning. Nature. 432: 144-146.

Boehm, H. D. V., and Siegert, F. 1999. Application of Remote Sensing and GIS to survey and evaluate tropical peat. Kalteng Consultants. International Conference and Workshop on Tropical Peat Swamps, Safeguarding a Global Natural Resource. 27-29 July 1999. Penang, Malaysia.

Brockelman WY, Ali R (1987). Methods of surveying and sampling forest primate populations. In Primate Conservation in the tropical rainforest. (Mittermeier RA, Marsh RW, eds); p^pp 23-62. New York: Alan Liss.

Brockelman WY, Srikosamatara S (1993). Estimation of density of gibbon groups by use of the loud songs. American Journal of Primatology 29:93-108.

Cattau ME (2010). USING THE ECOSYSTEM SERVICE VALUE OF HABITAT AREAS FOR WILDLIFE CONSERVATION: IMPLICATIONS OF CARBON-RICH PEATSWAMP FORESTS FOR THE BORNEAN ORANG-UTAN, Pongo pygmaeus. In Nicholas School of the Environment; p^pp.: Duke University.

Cheyne SM, Thompson CJH, Phillips AC, Hill RMC, Limin SH (2007). Density and Population Estimate of Gibbons (Hylobates albibarbis) in the Sabangau Catchment, , Indonesia. Primates 49:50-56.

Cowlishaw G (1996). Sexual selection and information content in Gibbon song bouts. Ethology 102:272-284.

Davies G (2002). Primates. In African forest biodiversity. (Davies G, ed); p^pp 99-116. Earthwatch Press.

Hamard MCL, Cheyne SM, Nijman V (2010). Vegetation correlates of gibbon density in the peat-swamp forest of the Sabangau catchment, Central Kalimantan, Indonesia. American Journal of Primatology 72:607-616.

IUCN (2008). Red List of Threatened Species. In; p^pp.: IUCN.

www.outrop.com @outrop facebook.com/outrop 6 Nijman V, Menken S, B.J. (2005). Assessment of census techniques for estimating density and biomass of gibbons (Primates: Hylobatidae). The Raffles Bulletin of Zoology 53:169-179. O’Brien TG, Kinnaird MF, Nurcahyo A, Iqbal M, Rusmanto M (2004). Abundance and distribution of sympatric gibbons in a threatened Sumateran rainforest. International Journal of Primatology 25:267-284.

www.outrop.com @outrop facebook.com/outrop 7 OuTrop: Gibbon Density Comparison

Wildlife Conservation Research Unit Department of Zoology University of Oxford The Recanati-Kaplan Centre Tubney House, Abingdon Road Tubney, Oxon, OX13 5QL, UK

Tel: +44 (0)1865 611119

www.wildcru.org

The Orangutan Tropical Peatland Project, 91 Jalan Semeru, Bukit Raya, Palangka Raya 73112, Kalimantan Tengah, Indonesia.

The Orangutan Tropical Peatland Trust, (registered UK Charity no.1142870), Wildlife Conservation Research Unit, Department of Zoology, University of Oxford, Recanati-Kaplan Centre, Abingdon Road, Tubney, Oxfordshire OX13 5QL, United Kingdom

www.outrop.com @outrop facebook.com/outrop