Eruption of Permanent Teeth in Japanese Monkeys (Macaca fuscata)

A total of 406 observations on dental eruption was obtained from 343 Japanese monkeys (Macaca fuscata) of known birthdays (Table 1). The order of the beginning of eruption was estimated as (M1, M1), (I1, I1), (I2, I2), (M2, M2), (PPPP), (C,, C'), (M3, M3) for male and (M1, M1), (I1, I1), (I2, I2), (M2, M2), (C,, P3, P3, C', P4, P4), (M3, M3) for female. Among 406 observations, 270 were used for statistics of the eruption age, because the remaining 136 which were obtained from monkeys of Shiga and Koshima show a fair degree of delay in th eruption age as a whole. The statistical results were shown in Tables 2 and 3, and a norm of the eruption age as a tentative interpretation was given in Table 4 with a footnote concerning the delay of eruption in monkeys of Shiga and Koshima. Interpretation of the delay in these monkeys is difficult, though the delay in monkeys of Koshima may be related to the general delay of their growth which has been caused by their isolation on a small islet. From the comparison of the present results and related reports on macaques (Table 5), it is apparent that among four species, M. fascicularis, M. mulatta, M. nemestrina and M. fuscata, the eruption is comparatively late in M. fuscata for most teeth, and it is generally earlier in female than male for every tooth except for M3 which erupts at similar age in both sexes or earlier in male than female especially in M. mulatta. Sexual difference in the eruption age of C, and possibly of P3, is relatively small in M. fascicularis and large in M. nemestrina. It seems that these interspecific differences are more or less related to those in body size and canine size.