History and Present Scope of Field Studies on Macaca fuscata yakui at Yakushima Island, Japan

Fermentation Ability of Gut Microbiota of Wild Japanese Macaques in the Highland and Lowland Yakushima: In Vitro Fermentation Assay and Genetic Analyses

Wild Japanese macaques (Macaca fuscata Blyth) living in the highland and lowland areas of Yakushima are known to have different diets, with highland individuals consuming more leaves. We aim to clarify whether and how these differences in diet are also reflected by gut microbial composition and fermentation ability. Therefore, we conduct an in vitro fermentation assay using fresh feces from macaques as inoculum and dry leaf powder of Eurya japonica Thunb. as a substrate. Fermentation activity was higher for feces collected in the highland, as evidenced by higher gas and butyric acid production and lower pH. Genetic analysis indicated separation of highland and lowland in terms of both community structure and function of the gut microbiota. Comparison of feces and suspension after fermentation indicated that the community structure changed during fermentation, and the change was larger for lowland samples. Analysis of the 16S rRNA V3-V4 barcoding region of the gut microbiota showed that community structure was clearly clustered between the two areas. Furthermore, metagenomic analysis indicated separation by gene and pathway abundance patterns. Two pathways (glycogen biosynthesis I and D-galacturonate degradation I) were enriched in lowland samples, possibly related to the fruit-eating lifestyle in the lowland. Overall, we demonstrated that the more leaf-eating highland Japanese macaques harbor gut microbiota with higher leaf fermentation ability compared with the more fruit-eating lowland ones. Broad, non-specific taxonomic and functional gut microbiome differences suggest that this pattern may be driven by a complex interplay between many taxa and pathways rather than single functional traits.

Primatology: the beginning

The journal Primates was founded by Kinji Imanishi (1902-1992) in 1957: It is the oldest and longest-running international primatology journal in the world. In this series of dialogues between Tetsuro Matsuzawa, Editor-in-Chief of Primates and the General Director of the Japan Monkey Centre (JMC) and Juichi Yamagiwa, former Editor-in-Chief of Primates and the Museum Director of the JMC, we look back at the achievements of our spiritual ancestors in primate research and talk about the back story of Imanishi and his fellow primatologists: founding the JMC as a research institute focused on primates and launching this journal. What was their motivation? What challenges did they face? What is their continued influence on the field right up to the present? What will be the legacy of our influence on the discipline?

Mycophagy among Japanese macaques in Yakushima: fungal species diversity and behavioral patterns

Mycophagy (fungus-feeding) by Japanese macaques (Macaca fuscata yakui) in Yakushima has been observed by many researchers, but no detailed information is available on this behavior, including which fungal species are consumed. To provide a general description of mycophagy and to understand how and whether macaques avoid poisonous fungi, we conducted behavioral observation of wild Japanese macaques in Yakushima and used molecular techniques to identify fungal species. The results indicate that the diet of the macaques contains a large variety of fungal species (67 possible species in 31 genera), although they compose a very small portion of the total diet (2.2% of annual feeding time). Fungi which were eaten by macaques immediately after they were picked up were less likely to be poisonous than those which were examined (sniffed, nibbled, carefully handled) by macaques. However, such examining behaviors did not appear to increase the macaques' abilities to detect poisonous fungi. Fungi that were only partially consumed included more poisonous species than those fully consumed with/without examining behavior, yet this was not significant. Taste, therefore, might also play an important role in discriminating poisonous from non-poisonous.