A lot of Japanese macaque (Macaca fuscata) fossil specimens have been discovered from the middle Pleistocene through Holocene deposits in Japan. Although some specimens are isolated molars, previous studies have not used them for statistic analyses, because it was difficult to identify their specific tooth class due to morphological similarities among teeth. In this study, we have applied a geometric morphometric method to explore the morphological differences among three classes of upper molars (M1-M3) in extant Japanese macaques, and assessed the reliability of the application of this method for fossil specimens. Canonical variate analysis revealed that there is a tendency for morphological differences among three classes of upper molars, as follows. M1 is characterized by the concavity of the external outline of the crown in the mesio-lingual region and its expansion on the buccal side of the mesial region and on the distal side of the buccal region, and lingual displacement of the protocone and hypocone. M2 tends to show the expansion of the external outline in the disto-lingual region and its slight concavity on the mesial side with mesial displacement of the metacone and hypocone. M3 is characterized by the expansion of the external outline in the mesio-lingual region and its concavity on the buccal side of the mesial region and on the distal side of the buccal region, and buccal displacement of the protocone and hypocone. All fossil molar specimens could be identified to their proper classes. Although improvement of this method is needed, it is now possible to identify the class of molars, even in isolated fossil specimens, and this may contribute to a better understanding of the evolutionary history of Japanese macaques.

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Primates can use various objects as tools. How they use the objects varies with the species. This provides a measure of primates' intelligence. This study focuses on the following issues on the ability of cotton-top tamarin's tool-use behavior shown by Santos et al.; 1) Whether does tamarin use an inverse model or a forward model as the internal model on the tool-use behavior? 2) How many steps of tools' movement can tamarin predict using the internal model when multiple tools are used? We present computational models that are expected to reproduce tamarin's behavioral data. The models are implemented with an actor-critic model of reinforcement learning and the internal model. We conducted computer simulations in which five agents (virtual actors) execute the same tool-use tasks as the tamarins did. The only one agent that uses the inverse model and predicts one tool's movement replicated Santos' results. This result suggests that the tamarins used the inverse model and predicted one tool's movement in the experiments by Santos et al.

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We observed 4 cases of aggressive response of Japanese macaques (Macaca fuscata) toward a Japanese giant flying squirrel (Petaurista leucogenys) at the feeding site of the Katsuyama group.
When a Japanese giant flying squirrel glided over to a tree at the feeding site, almost all the adult and subadult monkeys resting around the tree mobbed the flying squirrel with threatening sounds. Immature monkeys aged ≤ 2 years screamed, and the mothers retrieved their infants immediately on spotting the flying squirrel. Several peculiar high-rank adult males and females chased, threatened, and attacked the flying squirrel for 25-114 minutes, but mothers with infants seldom approached the flying squirrel. High-ranking adult males had a greater tendency to perform agonistic displays toward the flying squirrel than low-ranking adult males and females.
Our observation and previous reports about interspecific encounters suggest that Japanese macaques recognize the Japanese giant flying squirrel as being in the same category as raptors, which prey on Japanese macaques. This explains why the monkeys respond aggressively, which is typical of antipredator behavior, to the common behavioral features of the flying squirrel and raptor-gliding and descending nearby. However, this aggressive response does not seem to benefit monkeys in terms of avoiding predators because the flying squirrel is not actually a predator. There are 2 other possible benefits. Their sensitivity to behavioral features that resemble those of the raptors may improve their efficiency in terms of antipredator behavior towards actual predators such as raptors. In addition, adult or subadult male monkeys may display their fitness to potential mates by performing agonistic displays in response to the Japanese giant flying squirrel.
In order to better understand the relationship between Japanese macaques and other species, it is necessary to establish a system for collecting and sharing data on rarely observed cases.

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To make clear characteristics of spermatogenesis in testes of the orangutan (Pongo pygmaeus), we carried out a histological study using testicular samples from two individuals. Seminiferous epithelia were thick and those with the typical spermatogenetic cell arrangement were predominant. The interstitial tissue was abundant with many collagen fibers. The acrosomic system was clearly observed. We noticed twelve steps in the spermiogenesis. We could identify ten stages in a seminiferous cycle. We discussed characteristics of spermatogenetic patterns in the orangutan, comparing with the human, chimpanzee and gorilla.

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Geophagy (soil-eating) is one of the well-known behaviours in many primate species, but the factors influencing this behaviour have been less known. In the captive environment of Tama Zoological Park, 2 female Borneo orangutans (Pongo pygmaeus) showed geophagic behaviour that was restricted to a particular site in the naturalistic outdoor enclosure. We compared the properties of the soil at this site with those of soils from 7 other different sites in the enclosure to determine the differences between the soils. To this end, we examined the landform, vegetation type, the physical and chemical characteristics of the soils at these sites. The enclosure was situated on the hillside of secondary woodland comprising Fagaceae sp. with a gently sloping ridge on the east side and valley bottoms on the west side. The site at which the animals exhibited geophagic behaviour was located at the lowest area of the valley bottoms. We found that this area was thinly covered by a herbaceous layer with Gramineae sp., and most of ground surface was bare. The soil eaten by orangutans had a low density and was highly friable, soft, and wet. Chemical analysis revealed that the soil in the enclosure had a high Ca content (70-80%) and that soils at some points in the enclosure, including the soil at the site of geophagic behaviour, had high Fe and Mg contents. The site of geophagic behaviour was located at the bottom of the valley; therefore, soil ingredients may have accumulated easily in this soil. However, we could not find any definitive chemical factors to explain the geophagic behaviour of orangutans. One possible explanation is that since the site was bare with highly friable, soft, and wet soil, the orangutans would have been able to easily eat the soil from that site.

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