Using a principal component analysis of 17 craniometric items, male adult Japanese macaques (Macaca fuscata) from Yakushima, Koshima and Kinkazan islands are compared. In the scores of the first principal component, which represent over-all size, the monkeys from Yakushima are separated from the monkeys from the other two islands, because of their small size. In the second component scores, the monkeys from Kinkazan tend to be higher than those from Koshima.
Craniometric variability appears to be smaller in the Kinkazan monkeys than in the Yakushima or Koshima monkeys. Although the Koshima is small islet and the monkey population is also small, craniometric variation of Koshima monkeys is comparable to that of Yakushima monkeys.