The amount of crop damage caused by Japanese macaques on Yakushima Island has significantly decreased, thanks to the use of electric fences and other preventive measures. However, local people continue to request the capture of Japanese macaques that cause damage, raising concerns about the conservation of Japanese macaques. This study aims to understand the underlying structure of these problems and propose solutions by focusing on local people's perceptions of damage, rather than on quantitative criteria such as the amount or quantity of damage. We interviewed village leaders and farmers, inspected electric fences, and analyzed relevant documents. Based on these findings, we examined the local people’s perception of the damage and the factors that lead to it on a village- by-village basis. The results suggest that one of the current problems on Yakushima Island is occurring mainly in areas where home-grown fruit trees are cultivated, where crop damage occurs due to inadequate installation and management of electric fences. In these areas, negative perceptions of damage are often exaggerated, such that damage is regarded as large even if the actual amount of damage is small. Another problem is the gap between current pest control practices on Yakushima Island and ideal practices for managing Japanese macaque populations. This gap may stem from the unclear hunting policy presented by the local government, hunters' customs, and the hunting permit system. These two problems may be led to excessive hunting of Japanese macaques. To address these issues, we propose the establishment of a system to facilitate the management of electric fences, the creation of opportunities to mitigate the negative perception of damage, and the development of a more systematic approach to hunting Japanese macaque.

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The mammalian gut microbiome contributes to numerous aspects of host physiology, including nutrition, behavior, and the immune system. For mammals with plant-based diet, such as many primates, gut microbiome contributes significantly to energy harvest from the fibrous foods. Despite its funcitonal significance, the ecological and evolutionary mechanisms governing gut microbiome variation remain poorly understood. Given their wide diversity in diet, life histories and social systems, nonhuman primates represent an ideal model for exploring the co-evolution between mammals and their gut microbiota. In this review, we synthesize current evidence on how variation in feeding ecology and social behavior shapes gut microbiome composition and function in both wild and captive primates. Diet emerges as the most consistent and influential factor: differences in food type, availability, and seasonality across species or populations drive marked shifts in microbial diversity and fermentative capacity. The ability of the gut microbiome to rapidly adjust to dietary fluctuations is increasingly recognized as a key adaptive trait supporting primate dietary flexibility. However, human-induced dietary changes through provisioning, captivity, or habitat disturbance may result in reduced microbial diversity and functional alteration, bringing concerns to primate conservation. Beyond diet, social behavior plays a critical yet increasingly recognized role in structuring the primate gut microbiome. Affiliative interactions such as grooming and physical proximity facilitate horizontal microbial transmission, giving rise to the social microbiome - a shared pool of microbes circulating within social groups. For dispersing individuals, such transition to the group-specific gut microbiome may enable more efficient adaptation to unovel diets and environments. Moreover, in sympatric settings, microbial exchange between species may occur through shared dietary resources, space use, and substrate contact. Together, these findings underscore the ecological and evolutionary relevance of the gut microbiome and advocate for its integration into the study of primate behavior, adaptation, and conservation.

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