Investigating morphological characteristics of archaeological remains of Sus scrofa among the Ryukyu Islands, south west of the Japanese archipelago, is necessary to understand the origin and dispersal process of the modern Ryukyu wild boar (S. s. riukiuanus). For this purpose, we examined whether the shape of teeth, which are often well preserved at archaeological sites, is useful to distinguish morphological variation of S. scrofa. We photographed the occlusal outline of the lower teeth of five modern populations of the Ryukyu wild boar and two populations of the Japanese wild boar (S. s. leucomystax). The outlines of each tooth were digitized into landmark coordinates and statistically compared. The difference in shape among the populations was evaluated by calculating the distance of homologous coordinates among them.
Our results suggested that tooth outline shape is significantly different between the two subspecies. In addition, correct assignment rates of the populations based on their tooth shape was the highest for the fourth deciduous premolar, which showed that this tooth is the most useful for distinguishing variation of S. scrofa. The tooth outline shapes of geographically adjacent populations tend to be similar. Therefore, we concluded that the tooth outline shape is a powerful tool for distinguishing subspecies of S. scrofa as well as their geographical variation. This method is especially useful for archaeological remains, because of its applicability for isolated teeth, and has potential to increase our understanding about the history of migration and introduction of S. scrofa into the Ryukyu Islands.