Morphological variation of the Japanese raccoon dog: implications for geographical isolation and environmental adaptation

Abstract

To test the effect of geographical isolation by 'Blakiston's Line' and the possibility of Bergmann's rule being valid, we comparatively examined the morphology of the crania, mandible and teeth of two subspecies of raccoon dog allopatrically distributed in Japan: Nyctereutes procyonoides albus and Nyctereutes procyonoides viverrinus. The Blakiston's Line is a biogeographic border separating mammalian and avian fauna in Japan, including N. p. albus and N. p. viverrinus. Most skull measurements of N. p. albus were larger than those of N. p. viverrinus, suggesting that the body size of N. p. albus could also be larger than that of N. p. viverrinus. Both subspecies were clearly isolated by Blakiston's Line and followed Bergmann's rule, with skulls of the northern subspecies, N. p. albus, larger than N. p. viverrinus. Premolars and molars of N. p. viverrinus were larger than those of N. p. albus, suggesting that N. p. viverrinus may be more frugivorous. The narrow postorbital constriction associated with development of temporal muscles in N. p. albus suggests this subspecies is more carnivorous.

Sexual Dimorphism of Craniodental Morphology in the Raccoon Dog <i>Nyctereutes procyonoides</i> from South Korea

“…Nyctereutes procyonoides has originally held a wide distribution throughout East Asia, however, it has widely established itself throughout Eastern Europe, following introduction to the continent by man. The species shows remarkable geographic variation in the skull and teeth among both native and introduced populations [1,5,10,17]. The sexual dimorphism is reported to be relatively small in raccoon dogs [5,7,10,16], nevertheless, the degree of sexual dimorphism varies between its local populations [5,16].…”

“…The species shows remarkable geographic variation in the skull and teeth among both native and introduced populations [1,5,10,17]. The sexual dimorphism is reported to be relatively small in raccoon dogs [5,7,10,16], nevertheless, the degree of sexual dimorphism varies between its local populations [5,16]. To elucidate the factors which have influenced sexual dimorphism within raccoon dogs, an assessment of the geographic variation in sexual dimorphism should be helpful.…”

“…In N. procyonoides, there is only one study which has compared the regional differences in sexual dimorphism as noted above [16], though further authors have studied the dimorphism within one region [5,6]. In this study, we examined sexual dimorphism of the craniodental traits among South Korean specimens, which are regarded as a distinct subspecies, N. p. koreensis [15].…”

Overwintering strategy of wild free-ranging and enclosure-housed Japanese raccoon dogs (Nyctereutes procyonoides albus)

“…On the basis of morphological (Haba et al 2008) and genetic (Masuda 1994) distinctions and geographically non-overlapping distributions, the raccoon dogs of Japan are subdivided into two subspecies; N. p. viverrinus is native to the islands of Honshu, Shikoku and Kyushu, where the climate is relatively warm, while N. p. albus is native to the northern island of Hokkaido, which is separated from the main island of Japan by the "Blakiston's line", marking the transition to subarctic climate. In Hokkaido, N. p. albus has been traditionally considered to hibernate during winter, but no physiological recordings of T b exist.…”

Geographic Cline in the Shape of the Moose Mandible: Indications of an Adaptive Trend

“…On the contrary, the intra-specific level has received much less attention, despite the great geographic distribution and morphological variation in many ungulate species (Geist 1998). Yet, remarkable variation in the shape of the mandible related to differences in the habitat and diet has been reported in a few species of ungulates, such as the roe deer (Capreolus capreolus; Aragon et al 1998) and the sika deer (Cervus nippon; Ozaki et al 2007), as well as in studies on other mammalian taxa, including, e.g., the punaré rat (Thrichomys apereoides; Monteiro et al 2003), the wood mouse (Apodemus sylvaticus; Renaud and Michaux 2003), and the raccoon dog (Nyctereutes procyonoides; Haba et al 2008). …”