We reviewed previous literature on primate crop feeding in Asia. We found 134 reports from 14 different countries and regions. More than half of the crop feeding cases involved macaques, followed by colobines, especially common langurs, and to a lesser extent by orangutans. No crop feeding by gibbons, lorises, or tarsiers has been reported. Most reports obtained information about crop feeding through interviews with locals and recorded the crops damaged and troop composition, while a few recorded the activity of the target primates and their population parameters. Crop feeding increased when the field was located near the forest, and when natural food availability decreased. Most farmers used non-lethal countermeasures, while some farmers killed the monkeys, and a few used electrical fences to protect crops. In study sites inhabited by multiple animal species, primates are often the worst crop feeders. Human perception and attitudes toward crop feeding primates were affected by income, residential area, religion, and history of crop feeding. Recent studies have created models based on previous data to clarify the potential risk of crop feeding and to predict the monkeys' ranging patterns. To create models for reducing crop damage and to design conservation strategies, collecting fundamental information is necessary.

The populations of the Japanese macaque (Macaca fuscata), which were vulnerable until the early 20th century, have recently recovered. However, this recovery process has rarely been hailed as a conservation success, because it has triggered serious conflicts between people and the macaques. The key exacerbating causes of the conflicts have been the drastic changes in the interrelations between the people, forests, and macaques, as well as the unprecedented social changes in modern Japan (i.e., nationwide depopulation). The aim of this review was to illustrate the bigger picture of these conflicts, by untangling the key root causes, and presenting the outcomes of previous macaque management efforts, which have rarely been presented to the global scientific community. Although recently acquired knowledge regarding macaque management has the potential to support the development of future solutions for the human-macaque conflicts, inadequate responses to the key causes of the physical and psychological hollowing-out of communities across Japan, should be understood as a limiting factor for conflict resolution. This review demonstrates the significance of seeking a resolution for this problem under a wider framework, in order to restructure community designs to be appropriate for the new era of shrinking communities.

Habitats of the Japanese macaque (Macaca fuscata) have been modified by human activities such as deforestation, conifer plantation, agriculturalization, and forest fragmentation. Such modifications likely affect habitat use of the macaques. We examined the habitat use of two macaque troops: a “forest troop” and a “cropland troop”. We focused on forest edges, which have not been previously categorized as a habitat type. Both troops frequently used deciduous broad-leaved forest in autumn and forest edges in summer. The forest troop frequently used forest-grassland edges, whereas the cropland troop frequently used forest-cropland edges. The selection index for the deciduous broad-leaved forest of the cropland troop exhibited significantly higher values than those of the forest troop in summer, autumn, and winter. Since the Japanese macaque is a forest-dweller and tends to avoid open areas, both troops may have used forests more frequently. Meanwhile, a decline in food resources in the forest due to the establishment of conifer plantations and an increase in food resources due to agriculturalization may have led to more frequent use of forest edges by the macaques. Forest edges should be treated as an independent habitat for accurate assessment of macaque habitat use.

We studied home range use of crop-raiding Japanese macaques (Macaca fuscata) in Shiga Prefecture, central Japan, to address the effects of vegetation structure, specifically forest edge, on their habitat utilization. We compared the home range use of a troop inhabiting a rural area surrounded by a coniferous plantation with that of a troop inhabiting deciduous/coniferous forest mixed area. We then conducted a vegetation survey to evaluate the forest structure and food availability within their home ranges. Both troops frequently used the coniferous plantations and preferred them. The rural troop also preferred deciduous forest. Both troops preferred bamboo forest and avoided other vegetation types. The vegetation survey found that food availability in deciduous forest was the greatest. Both troops frequently used the forest edges, likely due to higher food availability as well as its role as a refuge. We found higher similarity in composition of food plant species between coniferous plantation and the deciduous forest, which implied that the former can be converted to the latter through thinning. We suggest an idea on the habitat management through thinning of the coniferous plantation to improve the present situation of the human-macaque conflict.

A decrease in the amount of crop damage by Japanese macaques (Macaca fuscata) is often defined as the primary official goal for conflict resolution. Recent government-led countermeasures have resulted in a decline in the amount of such damage, at least per the government statistics; however, residents rarely recognize this decline as a success of conflict management. We hypothesized that this unexpected perception of residents is because crop damage has changed not only quantitatively but also qualitatively, thereby affecting their perceptions of damage. We verified this hypothesis in terms of temporal variations influencing the psychological pressure on residents—that is, the geographical locations where severe crop damage occurred and the characteristics of macaque troops including their attitude toward residents—determined using multivariable analyses with questionnaire surveys and geographical information in Yamagata Prefecture, northern Japan. The results showed that the areas with severe crop damage had expanded to urban agriculture land, with a higher density of human population, and that the troop characteristics had changed substantially to facilitate this expansion. These findings support our hypothesis and indicate that the current attention of decision-makers is being, often and intensively, directed toward only the apparent total amount of damage.

For macaque management, it is recommended that residents use countermeasures, such as psychological attacks using fireworks and other to drive macaques away from farmland. However, these require settlement-wide cooperation and continuous implementation. I surveyed residents within settlements and aimed to clarify the conditions under which countermeasures were successful. I hypothesized that the effectiveness of countermeasures can be explained by the situation within the macaque-damaged settlements. A questionnaire survey such as the situation of the settlement, crop damage, and the state of macaque management was conducted in 2017 in each settlement of six municipalities in Niigata Prefecture. A gradient boosting model was used to predict the effects of psychological attacks and electric fences on multiple conditions. Of the 219 survey results, 193 settlements were affected by Japanese macaques. Several variables including the number of cooperative entities within the municipality, the number of settlement maintenance activities, and the degree of damage contributed to the effect of psychological attacks. Only the number of cooperative entities within the municipality contributed to the effect of the electric fence. The feasibility of implementing each of these countermeasures for macaque control could be predicted by assessing the situation in each settlement.

Japanese macaques and alien macaques have hybridized in the Boso Peninsula, Chiba Prefecture, Japan. In this study, the origin of the alien species was investigated by molecular assessments with mitochondrial DNA (mtDNA) and Y-chromosome genes. Maternal origin was assessed by comparing mtDNA sequence records. The results suggested that the alien species in the southern part of peninsula originated from the rhesus macaques in eastern China. Y-chromosome assessments with three microsatellite (Y-STR) loci detected a unique haplotype that is distributed in Japanese macaque habitats. Its origin was assessed by the TSPY (testis-specific protein on Y-chromosome) gene, suggesting the possibility of the involvement of long-tailed macaques in the Indochina region or rhesus macaques different from known source. Further investigation of historical documents and interviews disclosed the existence of a facility of long-tailed macaques planned for vaccine production in the past. This study presented novel evidence that the hybridization of Japanese macaques in the Boso Peninsula has the possibility to associate not only with rhesus macaques, but also with long-tailed macaques from the Indochina region. It is important to further monitor the status of Japanese macaques and changes in their hybridization in the peninsula for future conservation purposes.