Identifying priority areas for the conservation of the Critically Endangered northern white-cheeked gibbon Nomascus leucogenys in northern Lao
KHAMKEO S YX AIY AKHAMTHOR,DUSIT NGOPRAS ERT NORBE RT O ASE NSI O and TOMMASO S AV I N I
Abstract All gibbon species are declining throughout South and South-east Asia because of habitat loss and human activ- ities such as hunting. Lao still contains a relatively large area of forest habitat suitable for gibbons, but their status in the country remains poorly known. Here we present the first density estimate of the Critically Endangered northern white- cheeked gibbon Nomascus leucogenys in Nam Et-Phou Louey National Protected Area, northern Lao. We con- ducted gibbon surveys using an auditory sampling technique during May–August 2014 andMay 2015,at 40 sites, covering 125.6 km2. We applied N-mixture models to analyse group counts, investigating which landscape and human distur- bance covariates influenced the spatial variation of gibbon abundance across the study area. We estimated the average gibbon density to be 0.4 groups/
km2.Gibbon density was higher in mixed deciduous forest (0.74 groups/km2)than in evergreen forest (0.09 groups/km2),which could be a result of long-termhunting in evergreen forest
areas.Thus, future gib- bon protection plans should consider not only evergreen for- est as priority habitat, but also deciduous forest, which tends to receive less attention in conservation planning. We also highlight key areas containing gibbons where law enforce- ment patrols should be focussed, to limit threats such as poaching. Future forest management plans should aim to maximize the size and connectivity of suitable gibbon habitat, to enable exchange between subpopulations.
Keywords Density estimation, Lao, Nam Et-Phou Louey National Protected Area, N-mixture model, Nomascus leucogenys, northern white-cheeked gibbon
Introduction
KHAMKEO SYXAIYAKHAMTHOR,DUSIT NGOPRASERT and TOMMASO SAVINI (Corresponding author) Conservation Ecology Program, School of Bioresources and Technology, King Mongkut’s University of Technology Thonburi, Bangkhuntien, Bangkok 10150, Thailand E-mail
tommasosavini@gmail.com
NORBERTO ASENSIO Department of Social Psychology and Methodology of Behavioural Sciences, University of the Basque Country, Donostia-San Sebastián, Spain
Received 23 October 2018. Revision requested 19 November 2018. Accepted 28 November 2018. First published online 29 August 2019.
tation of animal populations for bush meat and pet trade (Hughes, 2017). The region has one of the highest deforesta- tion rates in the tropics (Stibig et al., 2014), and forest cover has declined by c. 11% since 1990 (Sodhi et al., 2004). The area is considered a biodiversity hotspot with numerous threatened and endemic species, where future land-use changes are expected to cause extinctions across a wide range of taxa (Sodhi et al., 2010). The gibbons of the tropical forests of South-east Asia are important seed dispersers (McConkey, 1999) but their numbers are declining because of habitat loss and hunting (Geissmann, 2007). Of the 16 extant gibbon species and 12 subspecies, four species and four subspecies are categorized as Critically Endangered on the IUCN Red List, and 12 species and six subspecies as Endangered (IUCN, 2016). The northern white-cheeked gibbon Nomascus leucogenys, native to the forests of Lao, Viet Nam and southern China (Harding, 2012), is categorized as Critically Endangered because its populations may have declined by .80% since 1990; i.e. over the course of c. three gibbon generations (Bleisch et al., 2008). The species has been affected by defor- estation caused by agricultural encroachment into montane areas, and by fuelwood and timber extraction from remain- ing forests, particularly in China and Viet Nam. In addition, it is hunted for food and traditional medicine (Geissmann et al., 2000). In China a small population in Xishuangbanna, southern Yunnan (Hu et al., 1989), may be on the edge of extinction (Fan & Huo, 2009), leaving the forests of Viet Nam and Lao as the species’ major remaining habitats. In Viet Nam, gibbon habitat is particularly fragmented, with only small residual forest patches (Geissmann et al., 2000), and Pu Mat National Park is one of the few sites where the species has not been extirpated, with an estimated 130 groups remaining (Bach & Rawson, 2011). The range of N. leucogenys in Lao stretches from the north-east (Phou Den Din and Nam Et-Phou Louey National Protected Areas) to the central region (Nam Kading National Protected Area; Duckworth, 2008; Hallam et al., 2015). The country still harbours a sizeable population of N. leucogenys because large areas of forest are difficult to access for humans and remain intact
S Oryx, 2020, 54(6), 767–775 © 2019 Fauna & Flora International doi:10.1017/S0030605318001515
outh-east Asia’s biodiversity is under serious threat because of habitat loss and degradation, and overexploi-
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