Ecology and conservation of the endemic Bawean warty pig Sus verrucosus blouchi and Bawean deer Axis kuhlii
E VA JOHANNA RODE-MARGONO,HANNAH KHWA J A MAR K RADEMAKER and GONO SEMI A D I
Abstract The island of Bawean, Indonesia, is home to the endemic Bawean warty pig Sus verrucosus blouchi and Bawean deer Axis kuhlii. Despite their threatened status, no long-term monitoring programme is in place for either species. Using random encounter and occupancy modelling based on 4,516 camera-trap days in 2014 and 2015 we aimed to provide population estimates and ecological data, includ- ing habitat preferences, for these species. For the Bawean warty pig we estimate an overall population size of 234–467 mature individuals and demonstrate a negative correla- tion between probability of occupancy and distance from villages. This preference for human-modified habitat has implications for human–wildlife conflict and hunting pres- sure for this species. The population of the Bawean deer could not be estimated because of the low number of en- counters, but we suggest that this indicates the population is considerably smaller than previously reported. As island endemics, the Bawean warty pig and Bawean deer are par- ticularly vulnerable to threats, and appropriate measures for safeguarding the species need to be taken.
Keywords Activity pattern, Axis kuhlii, Bawean, habitat preferences, occupancy modelling, population size, random encounter modelling, Sus verrucosus blouchi
Introduction
(Myers et al., 2000). Island biodiversity is particularly threa- tened by habitat loss and conversion, overexploitation and in- vasive species, andmore recently by effects of anthropogenic climate change (Fordham & Brook, 2010). Conservation of
T
EVA JOHANNA RODE-MARGONO (Corresponding author) andHANNAH KHWAJA The North of England Zoological Society/Chester Zoo, Upton-by-Chester, Chester, CH2 1LH, UK. E-mail
j.rodemargono@
chesterzoo.org
MARK RADEMAKER* Forest and Nature Conservation Program, Wageningen University,Wageningen, The Netherlands
GONO SEMIADI (
https://orcid.org/0000-0002-9351-9746) Research Centre for Biology, Indonesian Institute of Sciences, Cibinong, Bogor, Indonesia
*Previously at: Department of Animal Management, Van Hall Larenstein University of Applied Sciences, Leeuwarden, The Netherlands
Received 18 October 2017. Revision requested 17 November 2017. Accepted 24 July 2018. First published online 27 March 2019.
Study area
The 196 km2 island of Bawean, in the Java Sea, is dominated by semi-evergreen forest, with a dry season during June–
Oryx, 2020, 54(6), 892–900 © 2019 Fauna & Flora International doi:10.1017/S0030605318000996
he Sunda Islands of the Indonesian archipelago are amongst the world’s most biologically diverse regions
island endemics is thus of paramount importance to the preservation of biodiversity in South-east Asia. The island of Bawean is a small volcanic remnant in the
Java Sea, separated from mainland Java for c. 10,000 years (Meijaard, 2003). Its most prominent endemic mammals are the Critically Endangered Bawean deer Axis kuhlii and the Endangered Bawean warty pig Sus verrucosus blouchi. Populations of these species are believed to be small but stable (Bawean deer: 250–300, Semiadi et al., 2015;Bawean warty pig: 177–377, Rademaker et al., 2016). The Bawean warty pig has no protected status but the Bawean deer is protected by Indonesian law (Lampiran Peraturan Pemerintah Nomor 7 Tahun 1999 & Undang-Undang No. 5 Tahun 1990), is listed on CITES Appendix I (CITES, 2017) and is one of 25 species that the Indonesian government considers to be in need of special conservation attention (decree SK.180/IV-KKH/2015; Ministry of Environment and Forestry, 2015). The primary threat to the deer is thought to be the small size of the population (Semiadi et al., 2015), with a potentially decreased genetic diversity (Rahman et al., 2017a), and hunting or stress caused by feral hunting dogs (Nursyamsi, pers. comm.; Drygala & Semiadi, pers. comm.; Rahman et al., 2017a). Bawean warty pigs are actively hunted to protect crops from damage (Nijman, 2003; Rademaker, 2016). Apart from a 9-month camera-trap survey for Bawean
deer in 2014 (Rahman et al., 2017a) and a survey for Bawean warty pigs in 2015 (Rademaker et al., 2016), there has been no long-term study of the mammal biodiversity of Bawean. As a result, no data are available about the ecol- ogy and behaviour of wild populations of the island’s threa- tened endemic species (but see Rode-Margono et al., 2016a), which hinders effective conservation planning. The aims of our 13-month camera-trap study on Bawean
Island were to (1) provide relative encounter rates for all recorded species, (2) produce absolute population estimates for the Bawean warty pig, (3) investigate which habitat and environmental factors influence relative encounter rates, (4) examine activity patterns, social structure and reproductive patterns, and (5) compare our results for the Bawean deer to those of Rahman et al. (2017a).
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