A Comparison of Hylobatid Survey Methods Using Triangulation on Müller’s Gibbon (Hylobates muelleri) in Sungai Wain Protection Forest, East Kalimantan, Indonesia

Abstract

Density estimates are a common tool for assessing potential changes in primate populations over time and for evaluating important habitat characteristics such as preferred food sources. There are several different methods for estimating the density and population of wild primates, though the accuracy of these methods across different habitats and species is difficult to assess. We calculated the density of the population of Müller's gibbon (Hylobates muelleri) in the pristine and regenerating forest in Sungai Wain Protection Forest in East Kalimantan, Indonesia from May to July 2012. We collected data on the location of bonded pairs and compared the results of two different density estimate methods: triangulation and point transect sampling using Distance software. The triangulation method yielded population estimates of 486.9 ± SD 132.6 individuals in the pristine forest and 274.3 ± SD 179.0 in the regenerating forest. Distance analysis produced population estimates of 580.5 ± CV 20.6 and 388.4 ± CV 23.4 individuals for the pristine and regenerating forest, respectively. The difference in the density estimates between methods was not significant. We hypothesize that point transect sampling overestimated group density based on the unusually high estimate, Int J Primatol 5 Orangutan Tropical Peatland Project, Palangka Raya, Central Kalimantan, Indonesia but further investigation into the accuracy of point transect analysis using Distance with respect to gibbons is needed. We conclude that triangulation remains an important tool for hylobatid surveys because of its efficacy in locating gibbon groups using acoustic detection.

Population mapping of gibbons in Kalimantan, Indonesia: correlates of gibbon density and vegetation across the species’ range

“…For a rapid assessment of gibbon density under time and financial constraints, the triangulation me thod may be most appropriate , Hamard et al 2010, Gilhooly et al 2015. However, triangulation represents increased effort over other methods for several reasons.…”

“…Care must be taken not to extrapolate across a landscape without considering the habitat type/ subtype , Hamard et al 2010, Gilhooly et al 2015. With this project, we sought to address the following research questions:…”

“…These plots covered a total of 1000 m 2 at each set of 3 listening posts within the effective listening areas of ~3.5 km 2 representing a sample of the available habitat. Previous studies investigating relationships between forest structure and primate densities used plots of 10 × 10 m (Rendigs et al 2003, Blackham 2005, Hamard 2008, Gilhooly et al 2015. Ten plots per habitat were analysed, with the exception of 5 habitats, for which 6 plots per site were analysed because of time constraints.…”

“…Data from Sabangau are from Hamard et al (2010), data from Bawan and Mungku Baru are from Harrison et al (2010Harrison et al ( , 2012. Data from Tujang and Borah are from Cheyne et al (2012), and data from Sungai Wain are from Gilhooly et al (2015). DBH: diameter at breast height, CSA: cross-sectional area, MSF: mixed swamp forest; LIF: low interior forest; TIF: tall interior forest; Ex-MRP: ex-Mega Rice Project; NA: not available ulations.…”

Assessing Land Cover Changes and CO2 Emissions in Tropical Forests, 1998-2016: A Case Study of the Sungai Wain Protection Forest

“…Despite these serious forest losses and degradation, there is a lack of definitive information on the extent and pattern of land cover changes in the SWPF. Most research in the SWPF has concentrated on the ecology [24][25]27]. This current study, therefore, aims to address this issue.…”