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Recently, some primatologists have begun studying social customs, which had been neglected in research despite their importance to human culture. We observed embracing behaviors 64 times during 543.8 hours of focal animal sampling, targeting adult females in a wild group of Japanese macaques in Yakushima, Japan, and compared the results with those in macaques in Kinkazan. Embracing occurred immediately after the spontaneous pause of allogrooming, aggressions, and approach between dyads frequently exchanging antagonistic interactions, all of which are considered to be stressful conditions. Embracing in Yakushima may, therefore, serve to reduce stress; this may also be the case in Kinkazan. Despite this functional similarity, the forms of embracing in Yakushima are slightly different from those in Kinkazan. First, not only ventro-ventral embraces, but also ventro-lateral and ventro-dorsal embraces were found in Yakushima. Second, kneading another’s fur by rhythmically opening and closing the palm occurred in Yakushima, instead of a rhythmic, body-rocking movement in Kinkazan. Because we cannot devise genetic or ecological explanations for the subtle local differences in embraces, this type of behavior may be identified as the first evidence for social customs in wild Japanese macaques., ニホンザル初の社会的慣習を発見. 京都大学プレスリリース. 2015-02-10.

The mass mortality of wild Japanese macaques (Macaca fuscata Blyth) was observed in a warm temperate forest of Yakushima, southern Japan. Demographic changes of eight troops between August 1998 and August 1999 were studied and 56% of macaques disappeared from the five intensively studied troops. Mortality varied among troops: two troops became extinct, while another troop did not decrease in size. The rate of mortality of the other troops was between 33 and 80%. The variation in mortality among the troops was either the outcome of local concentrations of mortality or of intertroop competition. The rate of mortality decreased with increasing distance from the two extinct troops and with increasing troop size; these two factors could not be separated statistically. The direct cause of death was diagnosed as pneumonia for four out of five fresh carcasses. The fleshy fruit production in autumn 1998 was the lowest in 14 years, and macaques had relied on leaves earlier than in usual years. It was exceptionally hot and dry in the summer of 1998. The exceptionally poor fruit production and hot summer of this year, with the resulting shortage of high-quality foods, was consistent with the scenario that mass mortality was due to the poor nutritional conditions. However, the possibility that epidemics caused the mass mortality cannot be ruled out. Our findings proved that primates in a seemingly stable habitat experience fluctuations in demographic parameters under natural conditions.

A trade-off relationship between mating and feeding effort is important when considering reproductive strategies of long-lived species. I compared the influence of male sexual activities, female mate-choice behaviors and the daily activity budget on male mating success among males in a group of wild Japanese macaques (Macaca fuscata yakui) on Yakushima Island. The 1st-ranking male, which had immigrated into the troop at this rank, more frequently approached peri-ovulatory females, spent more time grooming peri-ovulatory females and in mounting series and spent less time feeding than subordinate males did. The 1st-ranking male attained the highest mating success as a result of his high expenditure of time and energy in sexual behaviors directed toward peri-ovulatory females. Mating success of subordinate males did not relate to the amount of sexual effort, but instead to the frequency of female approaches, female rush toward males and the number of peri-ovulatory females within the group. The pattern of intermale competition shifted from nearly contest competition to scramble competition as the number of peri-ovulatory females in the group increased. Feeding time of subordinate males did not vary between the days when they copulated and the days when they did not. The findings demonstrate that mate guarding in the 1st-ranking male is a high-cost mating tactic, while opportunistic mating in subordinate males is a low-cost mating tactic. The differences in male mating tactics are probably related to male life history and to the formation of groups with a high socionomic sex ratio.

In the previous research in 1993, three of the authors found that some troops of wild Japanese macaques were provisionized by tourists, around the road in the western forest of Yakushima Island, south of Kyushu, Japan. Again in 1995, we conducted a research with the same methods in the same area. Here we reported the results of 1995 and compared them with those of 1993.We surveyed the area along the road of 19.2km, passing through the forest. We set eight stations along the road as survey units, with a mean length of 2.4km. Each station was surveyed for two days. Each of us walked slowly in the station and searched troops of monkeys. When the observer found the monkeys on or near the road, he or she began observation session for maximum of 30 minutes. At the end of observation session, the observer began to search another troop.During the observation session, we recorded the activities of monkeys and conducted“orange tests”. In the “orange tests”, we showed an orange to a monkey and recorded its response. If the monkey accessed to the orange, it was determined as provisionized.Percentages of provisionized monkeys were significantly different among the stations. However, no significant difference was found between the results of 1993 and 1995. Numbers of traffic passing through the road per day was 138.5, which was larger by 40 than in 1993. Among the traffic in 1995, at least 60% was due to tourists.The numbers of provisionized monkeys did not increased distinctively during the two years. However, numbers of tourists visiting the area apparently increased and the percentages of provisionized monkeys increased in some of the stations. Therefore, we should continue to monitor the provisionized monkeys and to make efforts to stop tourists from feeding monkeys.

Sho-saiko-to (SST) is a Japanese modified, traditional Chinese herbal medicine (Kampo medicine) consisting of seven medical plants. We examined the effects of SST on formation and growth of squamous cell papillomas induced by 7,12-dimethylbenz(a)anthracene application in mouse skin. Chronic oral administration of SST reduced the incidence and growth of papillomas with the reduction of activities of succinate dehydrogenase and thymidylate synthetase, which were evaluated as the cell viability and DNA synthesis via the de novo pathway, respectively.

We have conducted long-term research on sympatric gorillas and chimpanzees in Kahuzi-Biega National Park since 1987. The demographic history of habituated gorillas has provided insights into their reproductive strategies. Infanticide by male gorillas, which has occurred frequently in the Virunga mountain gorilla population, had not been reported in Kahuzi for more than 20 years. However, soon after the large-scale killing of gorillas during a war in the late 1990s, it occurred three times within a few months. The infanticidal male might have discriminated between infants who were not his offspring and an infant whom he presumably sired based on past interactions with their mothers. At Kahuzi, births occurred most frequently during the period of ripe fruit abundance, and female Grauer’s gorillas show longer inter-birth interval than female mountain gorillas in the Virungas. A comparison of reproductive strategies among different gorilla populations suggests that seasonal fluctuation in food abundance may lead to slow reproduction, whereas the potential pressure of infanticide may promote rapid reproduction. The reduced ranges and increased encounters between unfamiliar groups induced by large human disturbance, such as wars or conversion of their habitat to farmland, might have produced conditions leading to infanticide.

This is the first report on an observation of food transfer by a mother to her offspring in wild Japanese macaques (Macaca fuscata yakui). On November 6, 1996, an adult female wild Japanese macaque stopped grooming her 1.5–1.6 yr old daughter in order to be groomed by a young male. Her daughter protested loudly for about 1 min. In response to her daughter's protest, the mother picked up a mature nut ofQuercus phillyraeoides that was lying near her right hand, and placed it in the daughter's mouth. The daughter's cries were immediately muffled and she silently ate the acorn's contents, and spat out the pericarp. We inferred that the daughter wanted to be groomed by her mother, not to receive food. This reported example of treatment resembling tool using behavior in response to an emotional outcry was precipitated by mother-offspring conflict in the natural habitat.

Methods for the identification of the sex and species of individuals from samples non-invasively taken from humans and gorillas were established. Amplification of a segment of amelogenin (AMG), which is an X–Y homologous gene, using two pairs of primers from human AMG, revealed both X- and Y-specific bands. The possibility of sex identification was examined by typing the AMG gene using hair and fecal samples from captive western lowland gorillas (Gorilla gorilla gorilla) in Japan and hair samples from wild eastern lowland gorillas (Gorilla beringei graueri) in the Kahuzi-Biega National Park, Democratic Republic of Congo, which were sexed by direct observation. Species-specific bands of AMG in gorillas and humans were identified by restriction fragment length polymorphisms analysis. These tests could be used for sexing unidentified individuals of wild western and eastern lowland gorillas, and screening contamination of human DNA from non-invasively acquired samples.

Sho-saiko-to (SST) and Juzen-taiho-to (JTT), Japanese modified Chinese herbal prescriptions, suppressed the activities of thymidylate synthetase and thymidine kinase involved in de novo and salvage pathways for pyrimidine nucleotide synthesis, respectively, in mammary tumors of SHN mice with the reduction of serum prolactin level. These results indicate that SST and JTT may have the anti-tumor effects on mammary tumors.