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Seasonal variations and sex differences in the nutritional status in two local populations of wild Japanese macaques (Macaca fuscata fuscata) were examined. It was hypothesized that the ecological condition and/or reproductive strategies of each sex determine the nutritional condition and its seasonal fluctuation in each sex. Morphometric measures such as body mass, thoracic and femoris circumferences, skinfold thickness in four places (triceps, biceps femoris, subscapular, and abdomen), and wet mass of mesenteric and omental fat were used for comparisons between sexes, seasons, and populations. Animals of the Shimane population were larger than those of the Boso population in most morphometric measures, abdominal skinfold, and mesenteric and omental fat mass, suggesting environmental and/or genetic differences in the two populations. Females of both populations had larger skinfolds and mesenteric and omental fat mass than males, indicating that females had more fat than males. Females showed seasonality in most measures, having two peaks of body mass, thoracic and femoris circumferences, abdominal skinfold, and mesenteric and omental fat masses in early spring and late fall. In contrast, males exhibited no clear seasonal variations for most measurements, except for biceps femoris and subscapular skinfolds, which showed peaks in summer. Most morphometric measurements significantly correlated to each other, particularly in females, but most skinfolds had no correlation with other measurements. These findings suggest that sexual dimorphism in body composition and its fluctuation may be affected by the different reproductive strategies of males and females.

The population genetic status of the Asian black bear Ursus thibetanus in the western part of Japan was examined using microsatellite DNA markers. Although three fragmented populations have been recognized in this region, i.e., the western Chugoku (WC), eastern Chugoku (EC), and northern Kinki (NK) populations, it was recently pointed out that the NK population has also been divided into two subpopulations, the western (WNK) and the eastern (ENK) populations. We examined the genetic status of these four populations based on their heterozygosities and the genetic distances (FST) between them. The mean observed heterozygosity, i.e., genetic diversity, of the six microsatellite loci examined, was significantly lower in WC (0.272; n = 52) and WNK (0.311; n = 66) than that in ENK (0.445; n = 67), respectively. Reflecting geographic distances among populations, FST was higher between WC and WNK (0.244) and between WC and ENK (0.229) than that between WNK and ENK (0.066), respectively. There was also low but significant genetic differentiation between the two nearest populations (WNK and ENK). Although the status of EC was not conclusively determined because of its small sample size (n = 24), its genetic diversity seemed to be at a level similar to that of WC and WNK. These results suggest that WC, which is isolated from the others, has been losing genetic diversity, and that WNK, which had been thought to form a relatively large population together with ENK, might be isolated genetically from other populations. WNK, as well as WC and EC, should be conserved intensively.

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