Distributional expansion and prediction of probability of appearance of wild boars (Sus scrofa) in Iwate Prefecture, Japan

Abstract

Wild boars (Sus scrofa) have been spotted since 2007 in various parts of Iwate Prefecture, Japan. We clarify the process of their distributional expansion and predict the probability of their future appearance using a species distribution model. After the first sighting in Oshu City in 2007, the number of sightings increased mainly in the southern part of the prefecture in 2011, and wild boars were seen throughout the prefecture in 2018. Crop damage from wild boars was first observed in 2012 and increased from 2014 to 2017. Based on these results, we propose that 2007–2010 was the immigration period, 2011–2017 was the expansion period, and 2018 or later was the established period for wild boar in Iwate Prefecture. We found that elevation, vegetation, and land use data were effective predictors of the probability of appearance of wild boars. We predicted the probability of appearance using data up to 2017 and compared it with actual appearance sites in 2018 and 2019; we confirmed that the sites with higher predicted probability actually appeared. In the future, the number of boars would increase from areas with a high probability of appearance, and boars would appear in these areas.