First ecological study of the Bawean warty pig (Sus blouchi), one of the rarest pigs on earth

Abstract

The Bawean warty pig (Sus blouchi) is an endemic pig species confined to the 192 km2 large island of Bawean in the Java Sea, Indonesia. Due to a lack of quantitative ecological research, understanding of natural history and conservation requirements have so far been based solely on anecdotal information from interviews with local people and study of captive and museum specimens. In this study we provide the first assessment of population and habitat preferences for S. blouchi by using camera trapping. From the 4th of November 2014 to January 8th 2015, we placed camera traps at 100 locations in the forested protected areas on Bawean. In 690.31 camera days (16567.45 hours) we captured 92 independent videos showing S. blouchi. Variation in S. blouchi trapping rates with cumulative trap effort stabilized after 500 camera days. An important outcome is that, in contrast to the suggestion of previous assessments, only S. blouchi was detected and no S. scrofa was found, which excludes hybridization threats. We fitted a Random Encounter Model, which does not require the identification of individual animals, to our camera-trapping data and estimated 172-377 individuals to be present on the island. Activity patterns and habitat data indicate that S. blouchi is mainly nocturnal and prefers community forests and areas near forest borders. Next to this, we found a positive relationship between S. blouchi occupancy, distance to nearest border, litter depth and tree density in the highest ranking occupancy models. Although these relationships proved non-significant based on model averaging, their presence in the top ranking models suggests that these covariables do play a role in predicting S. blouchi occurrence on Bawean. The estimated amount of sites occupied reached 58%. Based on our results, especially the estimation of the population size and area of occupancy, we determine that the species is Endangered according to the IUCN/SSC Red List criteria.