Bawean warty pig and Bawean deer 895


TABLE 1 Species that were detected during a 13-month camera–trap survey on Bawean Island (Fig. 1a), 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.


Species


Mammals Bawean deer Axis kuhlii


Sunda porcupine Hystrix javanica


Long-tailed macaque Macaca fascicularis


Common palm civet Paradoxurus hermaphroditus


Bawean warty pig Sus verrucosus blouchi


Reptile Common water monitor Varanus salvator


Birds Purple heron Ardea purpurea


Emerald dove Chalcophaps indica


Green junglefowl Gallus varius


Red List category1


CR LC LC LC EN


LC


LC LC LC


Regional status


Protected Protected


Not protected


Not protected


Not protected


Not protected


Not protected


Not protected


Not protected


Total RAI2


0.84 0.07


38.35 0.16


21.81 0.13


0.04 0.02 0.11


Mean RAI ± SD3


0.46 ± 2.44 0.09 ± 1.09


No. of videos


38 3


29.68 ± 34.12 1731 0.07 ± 0.49


7 15.77 ± 23.42 985 0.12 ± 1.11


0.16 ± 2.15 0.01 ± 0.19 0.04 ± 0.56


6


2 1 5


Camera-trap days until first detection


507 265 115


1188 49


526 595


3928 1722


% of total records


1.4 0.1


62.3 0.3


35.5 0.2


0.1 0.0 0.2


1CR, Critically Endangered; EN, Endangered; LC, Least Concern. 2All detections for a species summed for all camera traps over all days, multiplied by 100 and divided by the total number of camera-trap nights. 3Mean of the RAI of each camera trap.


(dusk), noon and midnight. We used a χ2 test to compare the frequency of observations between sunset and sunrise and between sunrise and sunset, the timings of which were obtained from the Astronomical Applications Department of the U.S. Naval Observatory.


Results


Relative encounter rates, distribution and habitat preferences


In total we accumulated 4,516 camera-trap days, with 2,278 independent videos of ninewildlife species (Table 1). Domes- tic species recorded were water buffaloes (2 videos), feral dogs (44), cats (14) and chickens (3). In addition, there were 28 videos of unidentified species of rats.We could not detect any significant difference in the relative abundance index be- tweenwet and dry seasons for either of the focal species (deer: RAI wet = 0.57, RAI dry = 0.38;W= 3,619.5,P = 0.498; warty pig: RAI wet = 16.51,RAI dry = 15.21;W= 3,427,P = 0.367). Baweanwarty pigs were present in the three largest forest


blocks but absent from the two smallest fragments and the western peninsula Gili Barat (Fig. 1b). Given the sensitivity of the data, we refrain from publishing distribution data for the Bawean deer. However, 90% of all videos were recorded


in a single area of c. 17 ha, with 29 videos recorded from only two camera traps. In all of these locations, camera traps also recorded feral dogs. Fifty-five camera-trap locations were excluded from oc-


cupancy analysis of the Bawean warty pig because of missing covariate information. Of the remaining 126 sites, Bawean warty pigs were detected at 59, giving a naïve occupancy of 0.47. The top-ranking model indicated only a negative influence of distance to nearest village on probability of


occupancy (−0.56 ± SD 0.24; Fig. 2).Moonlight, temperature and rainfall did not significantly influence detection prob- ability and all other site-level covariates for probability of occupancy were similarly unable to improve model fit, such that there were no competing models (ΔAIC,2). The revised model-derived estimate of occupancy for the Bawean warty pig was 0.59 ± SD 0.06, with a detection probability of 0.17.


Population size


Random encounter modelling based on the four trapping periods yielded variable population estimates for the Bawean warty pig, ranging from a minimum of 75 individuals in October and November to a maximum of 2,219 in June and July (Table 2). Our overall mean estimate across the entire study period is 351 mature individuals.


Oryx, 2020, 54(6), 892–900 © 2019 Fauna & Flora International doi:10.1017/S0030605318000996


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