Ecology and Conservation of the Endemic Bawean Warty Pig Sus Verrucosus Blouchi and Bawean Deer Axis Kuhlii

Ecology and conservation of the endemic Bawean warty pig Sus verrucosus blouchi and Bawean deer Axis kuhlii

E VA J OHANNA R ODE-MARGONO,HANNAH K HWAJA M ARK R ADEMAKER and G ONO S EMIADI

Abstract The island of Bawean, Indonesia, is home to the island endemics is thus of paramount importance to the endemic Bawean warty pig Sus verrucosus blouchi and preservation of biodiversity in South-east Asia. Bawean deer Axis kuhlii. Despite their threatened status, The island of Bawean is a small volcanic remnant in the no long-term monitoring programme is in place for either Java Sea, separated from mainland Java for c. , years species. Using random encounter and occupancy modelling (Meijaard, ). Its most prominent endemic mammals based on , camera-trap days in  and  we aimed are the Critically Endangered Bawean deer Axis kuhlii and to provide population estimates and ecological data, includ- the Endangered Bawean warty pig Sus verrucosus blouchi. ing habitat preferences, for these species. For the Bawean Populations of these species are believed to be small but stable warty pig we estimate an overall population size of – (Bawean deer: –, Semiadi et al., ;Baweanwarty mature individuals and demonstrate a negative correla- pig: –, Rademaker et al., ). The Bawean warty pig tion between probability of occupancy and distance from has no protected status but the Bawean deer is protected by villages. This preference for human-modified habitat has Indonesian law (Lampiran Peraturan Pemerintah Nomor  implications for human–wildlife conflict and hunting pres- Tahun  & Undang-Undang No.  Tahun ), is listed sure for this species. The population of the Bawean deer on CITES Appendix I (CITES, ) and is one of  species could not be estimated because of the low number of en- that the Indonesian government considers to be in need of counters, but we suggest that this indicates the population special conservation attention (decree SK./IV-KKH/; is considerably smaller than previously reported. As island Ministry of Environment and Forestry, ). The primary endemics, the Bawean warty pig and Bawean deer are par- threat to the deer is thought to be the small size of the ticularly vulnerable to threats, and appropriate measures population (Semiadi et al., ), with a potentially decreased for safeguarding the species need to be taken. genetic diversity (Rahman et al., a), and hunting or stress caused by feral hunting dogs (Nursyamsi, pers. comm.; Keywords Activity pattern, Axis kuhlii, Bawean, habitat Drygala & Semiadi, pers. comm.; Rahman et al., a). preferences, occupancy modelling, population size, random Bawean warty pigs are actively hunted to protect crops from encounter modelling, Sus verrucosus blouchi damage (Nijman, ; Rademaker, ). Apart from a -month camera-trap survey for Bawean deer in  (Rahman et al., a) and a survey for   Introduction Bawean warty pigs in (Rademaker et al., ), there has been no long-term study of the mammal biodiversity he Sunda Islands of the Indonesian archipelago are of Bawean. As a result, no data are available about the ecol- Tamongst the world’s most biologically diverse regions ogy and behaviour of wild populations of the island’s threa- (Myers et al., ). Island biodiversity is particularly threatened endemic species (but see Rode-Margono et al., a), tened by habitat loss and conversion, overexploitation and in- which hinders effective conservation planning. vasive species, and more recently by effects of anthropogenic The aims of our -month camera-trap study on Bawean climate change (Fordham & Brook, ). Conservation of Island were to () provide relative encounter rates for all recorded species, () produce absolute population estimates for the Bawean warty pig, () investigate which habitat EVA JOHANNA RODE-MARGONO (Corresponding author) and HANNAH KHWAJA The North of England Zoological Society/Chester Zoo, Upton-by-Chester, Chester, and environmental factors influence relative encounter CH2 1LH, UK. E-mail [email protected] rates, () examine activity patterns, social structure and

MARK RADEMAKER* Forest and Nature Conservation Program, Wageningen reproductive patterns, and () compare our results for the University, Wageningen, The Netherlands Bawean deer to those of Rahman et al. (a). 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 Study area University of Applied Sciences, Leeuwarden, The Netherlands   Received  October . Revision requested  November . The km island of Bawean, in the Java Sea, is dominated Accepted  July . First published online  March . by semi-evergreen forest, with a dry season during June–

Oryx, 2020, 54(6), 892–900 © 2019 Fauna & Flora International doi:10.1017/S0030605318000996 Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.234, on 30 Sep 2021 at 10:44:18, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605318000996 Bawean warty pig and Bawean deer 893

November and a wet season during December–May Data analysis (Hamada et al., ). Central to the island is an extinct vol- cano, which reaches  m altitude. All remaining forests on We report relative abundance for all species encountered,  Bawean are encompassed within the . km Bawean with the relative abundance index (RAI) defined as all inde- Island Nature Reserve and Wildlife Sanctuary and are pendent detections of a given species summed for all camera  under varying levels of protection (Semiadi & Meijaard, traps over all days, multiplied by , and divided by the ’  ; Fig. a). total number of camera-trap nights (O Brien et al., ). We employed a -hour interval to define independent events (Rovero et al., ; Rademaker et al., ). As data were not Methods normally distributed and could not be transformed, we used non-parametric Kruskal–Wallis tests and Mann–Whitney Data collection U post-hoc tests to check for differences in relative abundance index between seasons and locations. For the influ- Camera trapping took place during November – ence of habitat variables on encounter rates, we report December . We divided the forested area into , single-season occupancy modelling outcomes using the grid cells of  ×  m, and selected cells randomly Rv... (R Core Team, ) package unmarked (Fiske & as locations for  camera traps (Long Range IR/E, Chandler, ). We removed records that were incomplete Cuddeback, De Pere, USA), which were moved periodically because of missing covariate values. Models assessed the between locations. During August–October, because of in- effects of all previously described site-level covariates on creasing concern about the low numbers of deer recorded probability of occupancy, and the effects of the observation- up to then, we set five camera traps preferentially for deer, level covariates moonlight, temperature and rainfall on based on local advice. We assumed these locations were still probability of detection. Sample sizes for Bawean deer random for warty pigs. To prevent spatial autocorrelation, were too small to run these analyses. camera traps were spaced at least  m apart. In small forest To estimate population density using random encounter fragments, because of difficult terrain, we selected the first modelling we defined the camera-trap rate as the total num- random point and then placed subsequent camera traps ber of independent captures divided by the total number of every  m in a randomly generated direction. We set camera-trap days. We calculated absolute population num- camera traps to record -s videos, with a -minute interval bers for four trapping periods of – days. The random until the next trigger. encounter model assumes that the population is closed; At each camera trap location we recorded the latitude i.e. there is a fixed number of individuals in the area and longitude (with a global positioning system), altitude throughout the estimation period (Rowcliffe et al., ). and habitat variables. These included the major habitat As there is no immigration or emigration on Bawean, poten- type (rice cultivation: n = ;gardencultivation:n=; tial bias comes only from births and deaths, the effects of shrubland and degraded forest: n = ;teakplantation: which we assume to be negligible for the chosen trapping n=;tallforest:n=; community forest: n = ;fordefi- periods. We could not standardize period length because nitions see Rademaker et al., ), mean tree diameter of logistical challenges. We also report the combination of at breast height, mean tree height in a  ×  mplot all four periods because single periods violate the assump- around the camera-trap location, and tree density using tion of at least  camera-trap locations (Rovero et al., the T-square method (Rode et al., )withtwosample ). The random encounter model used here is described points (for details see Rademaker et al., ). We calcu- in detail in Rademaker et al. () and follows Rowcliffe lated the mean litter depth in four  ×  msubplotsin et al. (, , ). Day range was defined as the the corners of the plot. Distances to the nearest village mean speed of movement of the animals in front of the and protected area border (approximately coinciding camera in m/s, extrapolated to km/day and multiplied by with the forest border) were calculated in ArcGIS v. . the proportion of time spent active. The result of the ran- (ESRI, Redlands, USA). Minimum and maximum daily dom encounter modelling was multiplied by the mean temperatures and precipitation data were obtained from group size of the relevant species, as a group is the entity Sangkapura meteorological station. Lunar illumination of detection. However, the result must be considered to be was retrieved from MOONDV v.  (Thomas, ). For a minimum estimate, as a video may miss some individuals the random encounter model, we also recorded the angle in a social group. We extrapolated the estimated densities  of detection, radial distance at detection and distance trav- per km to the total protected area on Bawean to provide elled for the first three video records of Bawean warty pigs absolute population estimates. To account for the effects on each camera (Rowcliffe et al., ). We assumed these of uncertainty of parameter variables on uncertainty of parameter values to be valid throughout the trapping the density function, we used a propagation of error ap- period. proach, calculated in Rademaker et al. (). As only adult

FIG. 1 (a) Protected area zonation on Bawean Island (largely coinciding with forest boundaries), fragments of protected area (known as Bloks), and camera-trap locations used in this study, and (b) records of the Bawean warty pig Sus verrucosus blouchi, where the size of the circles indicates the relative abundance index (RAI) at a camera trap (defined as number of detections at a camera trap over all days, multiplied by  and divided by the total number of camera-trap nights).

individuals contribute to reproduction, we report the num- model would need at least  independent events (Rovero ber of mature individuals as the relevant population unit for et al., ). conservation purposes. We estimated the number of mature To analyse behaviour, group sizes and group patterns we individuals by multiplying the density estimate by the mean use descriptive statistics unless indicated otherwise. Diel ac- ratio of adult individuals on a video (fully grown, males with tivity patterns and proportion of time spent active were es- warts; Rode-Margono et al., ) to the total number of in- timated based on camera-trap detections, using the circular dividuals counted (the latter included juveniles and piglets). statistics software Oriana v.  (Kovach Computing Services, No random encounter model was produced for Bawean Anglesey, UK) and the R package activity (Rowcliffe et al., deer, as the highest number of encounters in a field ). We ran Wald tests for the statistical difference period was  videos (August–October), and a reliable between activity level estimates at sunrise (dawn), sunset

TABLE 1 Species that were detected during a -month camera–trap survey on Bawean Island (Fig. a), with their IUCN Red List status, regional status, total relative abundance index (RAI), mean RAI, number of video records, number of camera-trap days until first detection, and per cent of total records.

Red List Regional Total Mean No. of Camera-trap days % of total Species category1 status RAI2 RAI ± SD3 videos until first detection records Mammals Bawean deer CR Protected 0.84 0.46 ± 2.44 38 507 1.4 Axis kuhlii Sunda porcupine LC Protected 0.07 0.09 ± 1.09 3 265 0.1 Hystrix javanica Long-tailed macaque LC Not 38.35 29.68 ± 34.12 1731 115 62.3 Macaca fascicularis protected Common palm civet LC Not 0.16 0.07 ± 0.49 7 1188 0.3 Paradoxurus hermaphroditus protected Bawean warty pig EN Not 21.81 15.77 ± 23.42 985 49 35.5 Sus verrucosus blouchi protected Reptile Common water monitor LC Not 0.13 0.12 ± 1.11 6 526 0.2 Varanus salvator protected Birds Purple heron LC Not 0.04 0.16 ± 2.15 2 595 0.1 Ardea purpurea protected Emerald dove LC Not 0.02 0.01 ± 0.19 1 3928 0.0 Chalcophaps indica protected Green junglefowl LC Not 0.11 0.04 ± 0.56 5 1722 0.2 Gallus varius protected

 CR, Critically Endangered; EN, Endangered; LC, Least Concern.  All detections for a species summed for all camera traps over all days, multiplied by  and divided by the total number of camera-trap nights.  Mean of the RAI of each camera trap.

 (dusk), noon and midnight. We used a χ test to compare in a single area of c.  ha, with  videos recorded from only the frequency of observations between sunset and sunrise two camera traps. In all of these locations, camera traps also and between sunrise and sunset, the timings of which recorded feral dogs. were obtained from the Astronomical Applications Fifty-five camera-trap locations were excluded from oc- Department of the U.S. Naval Observatory. cupancy analysis of the Bawean warty pig because of missing covariate information. Of the remaining  sites, Bawean warty pigs were detected at , giving a naïve occupancy   Results of . . The top-ranking model indicated only a negative influence of distance to nearest village on probability of −  ±    Relative encounter rates, distribution and habitat occupancy ( . SD . ; Fig. ). Moonlight, temperature preferences and rainfall did not significantly influence detection probability and all other site-level covariates for probability of In total we accumulated , camera-trap days, with , occupancy were similarly unable to improve model fit, independent videos of nine wildlife species (Table ). Domes- such that there were no competing models (ΔAIC , ). tic species recorded were water buffaloes ( videos), feral The revised model-derived estimate of occupancy for the dogs (), cats () and chickens (). In addition, there were Bawean warty pig was . ± SD ., with a detection  videos of unidentified species of rats. We could not detect probability of .. any significant difference in the relative abundance index between wet and dry seasons for either of the focal species (deer: Population size RAI wet = ., RAI dry = .; W = ,.,P=.; warty pig: RAI wet = .,RAIdry=.; W = ,,P=.). Random encounter modelling based on the four trapping Bawean warty pigs were present in the three largest forest periods yielded variable population estimates for the Bawean blocks but absent from the two smallest fragments and the warty pig, ranging from a minimum of  individuals in western peninsula Gili Barat (Fig. b). Given the sensitivity October and November to a maximum of , in June and of the data, we refrain from publishing distribution data for July (Table ). Our overall mean estimate across the entire the Bawean deer. However, % of all videos were recorded study period is  mature individuals.

Social behaviour and reproduction

Mean group and litter sizes, and numbers of adults, are in Table . Sample sizes for Bawean deer were too low to investigate reproductive patterns, with immature individuals recorded only in April and August (Fig. a). Bawean warty pigs were recorded in small family groups (with or without males), pairs, and as single males. Changes in group structure over the year indicate a reproductive peak in the dry season, particularly in August (Fig. b).

Discussion

FIG. 2 Predicted occupancy (mean ± SD) of Bawean warty pigs Relative abundance, distribution and habitat preferences in relation to distance to nearest village. Our results indicate that occupancy of Bawean warty pigs is negatively correlated with distance to villages but not with  We obtained only two captures of deer over the first other measured covariates, such as tree height, density and –  months of our study (November January ), from diameter, habitat type, or distances to roads and protected   fully random trap positions. In the following months area borders. In contrast, Rademaker et al. ()founda –  (February July) we sampled an additional random loca- negative correlation between camera-trap rate and distance  ±  tions ( SD days/location), resulting in six more cap- to protected area border, as well as a preference for commu- tures of deer. The inclusion of five preferentially positioned nity forest. Our occupancy model may have been unable to –  traps during August October ( days/location) resulted in detect influences of habitat type because the majority of cam-    additional captures, ( %) of which were from a single eras were located in two habitat types: tall forest (%) and location. These records were insufficient to calculate a popu- rice cultivation (%). However, Bawean warty pigs have pre- lation estimate for the Bawean deer using random encounter viously been found to prefer semi-open cultivated habitat modelling. (Semiadi & Meijaard, ; Meijaard, ), and this may have been captured in our data by the higher probability of occupancy with closer proximity to villages. From a conserva- Activity patterns tion perspective this preference poses a risk to the pigs, as crop damage on Bawean Island is mainly combatted by hunting Captures of Bawean deer (n = ) indicated an overall activ- (Rode-Margono et al., b;Rahmanetal.,a); the use ity level of ., but Rayleigh tests did not detect significant of non-specific hunting methods (e.g. snares) and associated deviation from a uniform daily activity distribution (z = ., stress may also affect Bawean deer (BBKSDA East Java, ). P=.), suggesting this species may be cathemeral Captures of Bawean deer were restricted to two areas, (Fig. a). Nevertheless, deer tended to be more active at with the majority of videos originating from a single loca- dusk than dawn (P = .) or midday (P , .), with a tion. Rahman et al. (a) detected high abundance in mean activity time of . ± circular SD  minutes. the same area and presence in a third location, using camera Records of Bawean warty pigs (n = ,) indicated an over- traps, and identified a low number of faecal samples in a all activity level of ., with Rayleigh tests showing an fourth location. They did not detect deer in the area uneven distribution of daily activity (z = .,P, .; where the other % of our videos were recorded. Fig. b). Pigs were most active at dawn (P , . for all pair- Rahman et al. (b) suggested that Bawean deer prefer wise comparisons; mean activity time was . ± circular secondary forest over primary forest, possibly because SD  minutes), with a second peak at dusk (P , .), and of higher productivity. Furthermore, they reported that were least active at midday (P , .; Wald tests), indicating Bawean deer use forests as refuges and edge habitat for for- a tendency for crepuscular activity patterns. There was no aging, which puts them at risk of conflict with people and pre- significant difference in number of encounters between dation by feral hunting dogs. Although we could not analyse  day and night for either species (warty pig: χ = .,df=, habitat preference because of insufficient data, the distribu-  P=.; deer: χ = .,df=,P=.). However, given tion of our records confirms the deer’s occurrence in commu- the limited number of records of the Bawean deer, the nity forests and tall forests near forest edges, but not in the observed activity patterns for this species need to be interior of the island, which is presumably primary forest. interpreted cautiously. The apparent absolute avoidance of some parts of the

TABLE 2 Details of the four camera-trap surveys and of the combined surveys, camera trapping parameter estimates, adjustment factors (used to estimate total population size and number of mature individuals), and model output and adjusted model output for the random encounter model for the Bawean warty pig over four periods in , and combined for the whole period.

Survey period Combined periods 7 Feb.–14 Apr. 22 May–1 Aug. 29 July–19 Oct. 21 Oct.–3 Dec. 7 Feb.–3 Dec. (67 days) (72 days) (83 days) (44 days) (266 days) Truncated operation 27 18 49 36 18 length (days) No. of camera traps 12 16 19 21 68 Parameter estimates Trap rate1 0.398 0.618 0.536 0.050 0.471 Day range (km/day)2,3 12.069 12.069 12.069 12.069 12.069 Radial distance (km)2,4 0.004 0.004 0.004 0.004 0.004 Angle2,4 (radians)1 0.392 0.392 0.392 0.392 0.392 Adjustment factors Mean group size 1.78 2.29 2.08 1.78 2.04 Proportion immatures 0.419 0.502 0.547 0.378 Model output Density (individuals/km2) 13.81–24.59 19.95–45.69 14.94–31.06 1.62–2.88 8.41–16.82 Adjusted model output Estimated population size 635–1,146 930–2,219 696–1,448 75–134 392–784 Estimated no. of mature 369–666 463–1,105 315–656 47–83 234–467 individuals

 Total number of independent captures divided by total number of camera-trap days.  From Rademaker et al. ().  Defined as the mean speed of movement of animals in front of the camera in m/s, extrapolated to km/day and multiplied by the proportion of time spent active.  Radial distance and angle of detection to the camera were measured at the time of detection of the animal in front of the camera.

protected area, or whether this is a relic of population dynam- precipitation and associated occurrence of fires, could result ics in a very small population, requires investigation. in large fluctuations in population sizes. Hunting pressure, Neither Rahman et al. (a) nor our study detected spatial restriction on dispersal and an absence of predators deer in the interiors of protected areas. The lack of records may exacerbate these changes. may be attributable to () a genuine absence or extreme Based on the findings of Rademaker et al. (), rarity in these areas, () secretive behaviour, with a strong which indicated a small and geographically restricted preference for moving in dense habitat that is difficult to population numbering ,  mature individuals, the monitor with camera traps, () adverse habitat conditions Bawean warty pig was categorized as Endangered on that are not suitable for Bawean deer, or () good conditions the IUCN Red List based on criterion D (IUCN, ). outside these areas attracting the deer. Similarly, Bawean Our new estimated mean of  mature individuals ex- warty pigs appear to be less abundant in the interiors of pro- ceeds this threshold. However, in line with IUCN guide- tected areas. It is important to understand the reasons for lines we suggest that because seasonal population sizes the lower abundance or absence of species in the protected are well below the threshold, the species may continue area interior, to plan effective conservation measures. to fulfil criterion D. Additionally, criteria B,(a,b(i,iii)) may qualify the species as Endangered based on the small extent of occurrence and area of occupancy Population estimates of Bawean warty pigs (IUCN, ). Population estimates per survey period for the Bawean warty pig fluctuated considerably across the duration of Population estimates of Bawean deer our study. Our lowest estimates were at the end of the dry season and beginning of the rainy season, whereas the high- Rahman et al. (a) calculated a population size of – est estimates were recorded in the dry season when the re- Bawean deer, suggesting a population equal to that of productive season was at its peak. Other studies have shown warty pigs (based on this study and Rademaker et al., that pig densities seem to fluctuate in response to resource ). The authors recorded  independent camera-trap availability (e.g. Hancock et al., ). Significant climatic images of deer from  camera positions during  months seasonality on Bawean Island, particularly in terms of in . A subset of the data was used to derive population

TABLE 3 Mean group size, mean litter size, and numbers of adult females, adult males and adults of indeterminate sex, of Bawean deer and the Bawean warty pig recorded in .

Species Bawean deer Bawean warty pig Mean group size ± SD 1.08 ± 0.27 (1–2) 2.04 ± 1.44 (1–9) (range) Mean litter size ± SD 1 ± 0 (1, 2) 2.12 ± 1.14 (1–6, 376) (range, n) No. of adult females 0.45 ± 0.50 (0–1) 0.50 ± 0.63 (0–4) (range) No. of adult males 0.47 ± 0.51 (0–1) 0.26 ± 0.49 (0–2) (range) No. of adults of inde- 0.07 ± 0.27 (0–1) 0.30 ± 0.60 (0–4) terminate sex (range)

FIG. 3 Activity plots based on camera-trap records of (a) the Bawean deer Axis kuhlii (n = ) and (b) the Bawean warty pig (n = ).

estimates using random encounter modelling. The subset contained  independent captures from  preferentially and  randomly positioned traps. The authors stated that there was no significant difference in trap rates between their random and preferential traps, although they provided no statistical test. In contrast, in our study we observed ()a large difference in trap rates between random and preferential traps, and () a highly localized population of deer. Based on the ratio of the number of independent captures of pigs and deer, we argue it is impossible for the population of deer to equal or exceed that of pigs. This discrepancy in FIG. 4 Monthly patterns of mean group size and structure based findings for a Critically Endangered species merits atten- on camera-trap records of (a) the Bawean deer (n = ) and tion, and could derive from differences in random encoun- (b) the Bawean warty pig (n = ). ter modelling, study design or deer ecology. Firstly, the random encounter modelling density equation is highly sensitive to parameter values, and thus measurement errors Rahman et al. (a) regarding repositioning of unsuccess- in the speed of movement, detection radius and/or detection ful traps to new positions makes it impossible to compare angle could result in overestimation. For example, Rahman the results objectively. However, if these traps were reposi- et al. (a) stated that most of the deer recorded in their tioned from their unsuccessful location, yet still considered videos were foraging, which could have been because a to be random, this could explain the high trap rates and number of traps were placed preferentially. Despite the hence the higher density estimation compared to our encounter rate between randomly and preferentially placed study. Additionally, even though trapping rates between camera traps not being significantly different, the high random and preferential camera traps may be statistically frequency of foraging will have had a negative effect on different, absolute numbers of these rates may also vary, the species’ estimated speed of movement, and thus a yielding different random encounter modelling results. positive effect on the estimated density. Secondly, contrary Thirdly, the difference may be related to the ecology of to the results of Rahman et al. (a), we found a large dif- Bawean deer. The closely related hog deer Axis porcinus, ference in the trap rate between our randomly and pref- for example, shows strong interannual fluctuations in popu- erentially positioned traps. Vagueness in the methods of lation size (J.W. Duckworth, pers. comm.). If fluctuations

were large enough to cause the observed discrepancies in conservation breeding programmes, and any releases should captures, this would suggest a serious decline in numbers. follow the IUCN Reintroduction Guidelines (IUCN/SSC, Although we cannot identify the exact source of the dis- ) to prevent any negative impact on the wild, released crepancy, we suggest that based on our data from , num- and captive insurance populations. bers of Bawean deer are considerably lower than the estimates based on data from  provided by Rahman et al. (a). Acknowledgements We thank the Indonesian Ministry of Research and Technology, the Center for Conservation of Natural This heightens concern for the future of the species. Resources (BBKSDA) in Surabaya and the Research Center for Biology—Indonesian Institute of Sciences (LIPI) for granting us permits for this research. We are grateful for the assistance and support Behaviour and ecology of Nursyamsi, head of Bawean protected area management, and the rangers Abdul Rahim, Maskur, Halim, Taha and Abdullah. This Bawean warty pigs showed significant activity peaks in the study was funded by the Zoological Society for the Conservation of morning and evening, which supports previous research by Species and Populations (Zoologische Gesellschaft für Arten und ’ Rademaker et al. (). Crepuscular behavioural patterns Populationsschutz), the People s Trust for Endangered Species, Los in the European wild boar Sus scrofa in South-east Asia Angeles Zoo and Botanical Gardens, and the Species Conservation Foundation (Stiftung Artenschutz). have been attributed to poaching and human disturbance (Gray & Phan, ); however, although poaching occurs Author contributions Study design and development, project co- on Bawean Island, it has not been quantified, and any effect ordination, supervision of field team, data analysis, writing: EJRM; on pigs’ activity patterns is unclear. Activity graphs for data analysis, editing: HK; study design and development, project Bawean deer indicate some diurnal activity, with a tendency research, supervision of field team, data analysis, editing: MR; advice on project design and development, editing: GS. towards crepuscularity. A similar pattern is reported for the closely related hog deer, for which hunting may cause an Conflicts of interest None. increase in nocturnal activity (Dhungel & O’Gara, ). Group composition of Bawean warty pigs seems to be Ethical standards This research complies with the Oryx Code of variable, with males sometimes staying in family groups Conduct for authors. Permits were issued by the Indonesian Ministry for Research and Technology (RISTEK) and the Ministry of when immature individuals are present. Our mean group Forestry’s Center for Conservation of Natural Resources (BBKSDA)  – size of (range ) is significantly lower than the previously (permit numbers: 367/SIP/FRP/SM/X/2014, 89/SIP/FRP/SM/III/ reported mean group size of . (–), despite our mean lit- 2015 and SIMAKSI no. SI.21/BBKSDA.JAT-2.1/2014). ter size of . (–) being similar to the previously reported . (–) (Rode-Margono et al., a). Our data indicate References that the reproductive peak in Bawean warty pigs occurs in the middle of the dry season, with no immature individuals BBKSDA EAST JAVA () Monitoring Satwa Flagship Jenis Rusa observed during the peak of the wet season. Increased repro- Bawean. Unpublished report. Balai Besar Konservasi Sumberdaya Alam Jawa Timur, Surabaya, Indonesia. duction in the dry season has also been recorded for the CITES () Convention on International Trade in Endangered  Philippine warty pig Sus philippensis (Oliver, ). Species of Wild Fauna and Flora. Appendices I, II and III. Http:// For Bawean deer, only single adults, pairs, or mothers cites.org/eng/app/appendices.php [accessed  September ]. with infants were observed. This social organization is in DHUNGEL, S.K. & O’GARA, B.W. () Ecology of the hog deer contrast to the situation in captivity, in which animals are in Royal Chitwan National Park, Nepal. Wildlife Monographs, , –. often held in large groups. Offspring were observed only FISKE,I.&CHANDLER,R.() Unmarked:anR package for fitting twice, with a single fawn in each case, as is common for hierarchical models of wildlife occurrence and abundance. Journal deer species. of Statistical Software, , –. FORDHAM, D.A. & BROOK, B.W. () Why tropical island endemics are acutely susceptible to global change. Biodiversity and Conclusions Conservation, , –. GRAY, T.N.E. & PHAN,C.() Habitat preferences and activity The conservation of islands should be considered a top pri- patterns of the larger mammal community in Phnom Prich Wildlife  – ority because of high species endemism and extinction risk Sanctuary, Cambodia. The Raffles Bulletin of Zoology, , .  HAMADA, J.I., YAMANAKA, M.D., MATSUMOTO, J., FUKAO, S., (Kier et al., ). 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