Geographical Variation of Mandible Size and Shape in the Japanese Wild Pig (Sus scrofa leucomystax)

Abstract

ABSTRACT. The mandibles of the Japanese wild pigs (Sus scrofa leucomystax) from various geographical locations, which have been stored in the University of Tokyo and National Science Museum, Tokyo were examined. The mandibles from northern localities were larger in size than those from southern localities. The Oita population was significantly smaller than the Honshu populations. The Mie population was smaller than the Hyogo population in length from the angle of the mandible. In the multivariate analysis, the Kyushu populations could be obviously distinguished from the Honshu populations in the principal component charts. However, each Honshu population did not show the locality-specific distribution of the principal component plots.KEY WORDS: Japanese wild pig, mandible, osteometry, principal component analysis.J. Vet. Med. Sci. 62(8): 815-820, 2000 The wild pig in Japan has been taxonomically separated into two groups [4,5,9,14,16,17,23]: (1) the Japanese wild pig (Sus scrofa leucomystax) in Honshu, Shikoku and Kyushu Areas and (2) the Ryukyu wild pig (Sus scrofa riukiuanus) in Nansei Islands. While the latter has been osteometrically examined and described in detail [6-8, 12-14, 25, 26], the Japanese wild pig has not been clarified by morphological characteristics except for a few reports [1,10]. The geographical variation in particular remained unclear among various populations of the Japanese wild pig, although the animal is largely distributed in forests in the Japanese mainland. MATERIALS AND METHODSThe measurement items (Table 1, Fig. 1), and the methods of sex and age determination are based on previous reports [2,3,10,11]. The locality data was dependent on the biological records accompanied with each specimen (Table 2, Fig. 2). We cited generally the localities at the level of prefecture in Table 2. The specific localities detailed, however, are arranged in Fukushima, Nagano and Miyazaki populations with detailed records. We examined a total of 174 mandibles of the Age groups III, IV and V from various populations (Table 2). These specimens has been collected and stored in the Laboratory of Veterinary Anatomy, The University of Tokyo and the Department of Zoology, National Science Museum, Tokyo.The mandible measurement was carried out in 20 items with a vernier caliper to the nearest 1 mm. We have already published the measurement data of the specimens stored in the University of Tokyo in previous studies [10], and used these measurement values for the present statistical study. The mean values of length from the angle (LA) were compared by Student's t-test between localities to clarify the size tendency among various populations of the Japanese wild pig. All data measurements were applied for the principal component analysis to elucidate the size and shape variation among pop lations. The package software of the multivariate analysis (Shakai-Joho Service, Tokyo) added in Microsoft Excel 98 was used in this analysis. RESULTSThe mean value and standard error of 20 measurements are given in Table ...

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