抄録
To determine the age of the bear, the so-called cementum-layer aging technique of the teeth has been tested for grizzly, Ursus arctos, and black bear, Ursus americanus, by many American researchers. We successfully applied the same technique for age determination of Yeso brown bear, Ursus arctos yesoensis, which inhabits Hokkaido, Japan. The animals examined consisted of 8 captive bears of known-age and 2 wild bears of unknown-age but adult. The fourth premolar teeth P4 and sometimes the canines were extracted from the skulls which were removed from freshly killed bears and cleaned for analysis. Thin longitudinal sections of the teeth were made for examination. When stained with hematoxylin, dark-staining layers (annuli) appeared in the section as reported for Amercian bears. The teeth of a yearling show no annulus. After the first year there appear different stained cementum layers, namely 1 annulus in the individual older than 1 year, 2 annuli in ones older than 2 years and so on. The oldest female adult we tested was 11 years 11 months old, having 11 annuli in both the fourth premolar and in the canine.
