Age Determination in the Yellow Weasel , Mustela sibirica coreana ”

The age of 116 males of the yellow weasel, Musteh sibirica corema, was de termined by the cementum-layer of the canine tooth, and the characters of the baculum. Six age classes (from the yearling to the five-year age class) were distinguished by the dental annuli. The one-year age class involved many individuals, and was followed by the two-year age class and then the yearling one in the number. On the o ther hand, the spec imens over three-year age c lasses were ra re . A survivorship curve based on the age composition indicated that 77 % of the population might die within two years of life for some reason. The mean of the ecological longevity for this species was calculated at about 2.1 years. There was a significant difference in the baculum weight between the group below the two-year age class and that of the two-year age class and over. The shape of the bacu lum used in conjunction with the baculum weight provided a fairly reliable clue for aging the weasels. Thus, the individuals below the two-year age class were regarded as juveniles, and those of the two-year age class and over as adults.