Bawean warty pig and Bawean deer 899
were large enough to cause the observed discrepancies in captures, this would suggest a serious decline in numbers. Although we cannot identify the exact source of the dis-
crepancy,we suggest that based on our data from2015, num- bers ofBawean deer are considerably lower thanthe estimates based on data from 2014 provided by Rahman et al. (2017a). This heightens concern for the future of the species.
Behaviour and ecology
Bawean warty pigs showed significant activity peaks in the morning and evening, which supports previous research by Rademaker et al. (2016). Crepuscular behavioural patterns in the European wild boar Sus scrofa in South-east Asia have been attributed to poaching and human disturbance (Gray & Phan, 2011); however, although poaching occurs on Bawean Island, it has not been quantified, and any effect on pigs’ activity patterns is unclear. Activity graphs for Bawean deer indicate some diurnal activity, with a tendency towards crepuscularity. A similar pattern is reported for the closely related hog deer, for which hunting may cause an increase in nocturnal activity (Dhungel & O’Gara, 1991). Group composition of Bawean warty pigs seems to be
variable, with males sometimes staying in family groups when immature individuals are present. Our mean group size of 2 (range 1–9) is significantly lower than the previously reported mean group size of 4.6 (1–7), despite our mean lit- ter size of 2.1 (1–6) being similar to the previously reported 2.5 (1–4) (Rode-Margono et al., 2016a). Our data indicate that the reproductive peak in Bawean warty pigs occurs in the middle of the dry season, with no immature individuals observed during the peak of the wet season. Increased repro- duction in the dry season has also been recorded for the Philippine warty pig Sus philippensis (Oliver, 1993). For Bawean deer, only single adults, pairs, or mothers
with infants were observed. This social organization is in contrast to the situation in captivity, in which animals are often held in large groups. Offspring were observed only twice, with a single fawn in each case, as is common for deer species.
Conclusions
The conservation of islands should be considered a top pri- ority because of high species endemism and extinction risk (Kier et al., 2009). Bawean Island is no exception, with population sizes of c. 350 Bawean warty pigs and, we argue, considerably fewer Bawean deer. The initiation of effective and standardized monitoring is required urgently to facilitate the conservation of these species. Considering the extremely low numbers and limited geographical distribution of wild Bawean deer populations, insurance populations should ideally be developed through managed
conservation breeding programmes, and any releases should follow the IUCN Reintroduction Guidelines (IUCN/SSC, 2013) to prevent any negative impact on the wild, released and captive insurance populations.
Acknowledgements We thank the Indonesian Ministry of Research and Technology, the Center for Conservation of Natural Resources (BBKSDA) in Surabaya and the Research Center for Biology—Indonesian Institute of Sciences (LIPI) for granting us per- mits for this research. We are grateful for the assistance and support of Nursyamsi, head of Bawean protected area management, and the rangers Abdul Rahim, Maskur, Halim, Taha and Abdullah. This study was funded by the Zoological Society for the Conservation of Species and Populations (Zoologische Gesellschaft für Arten und Populationsschutz), the People’s Trust for Endangered Species, Los Angeles Zoo and Botanical Gardens, and the Species Conservation Foundation (Stiftung Artenschutz).
Author contributions Study design and development, project co- ordination, supervision of field team, data analysis, writing: EJRM; data analysis, editing: HK; study design and development, project research, supervision of field team, data analysis, editing: MR; advice on project design and development, editing: GS.
Conflicts of interest None.
Ethical standards This research complies with the Oryx Code of Conduct for authors. Permits were issued by the Indonesian Ministry for Research and Technology (RISTEK) and the Ministry of Forestry’s Center for Conservation of Natural Resources (BBKSDA) (permit numbers: 367/SIP/FRP/SM/X/2014, 89/SIP/FRP/SM/III/ 2015 and SIMAKSI no. SI.21/BBKSDA.JAT-2.1/2014).
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Oryx, 2020, 54(6), 892–900 © 2019 Fauna & Flora International doi:10.1017/S0030605318000996
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