There is some variation in the colour of the ventral body and tail: it may be white to gray, dark gray mottled with white, or blackish. The populations in different geographic regions of Taiwan reveal a unique composition of ventral colouration: the eastern population is exclusively blackish (100%), the central and southern populations are mainly white to gray (both 80%), and the proportions of blackish and white-gray morphs in the northern population are 60% and 30%, respectively.