Diet-related factors strongly shaped the gut microbiota of Japanese macaques.

Although knowledge of the functions of the gut microbiome has increased greatly over the past few decades, our understanding of the mechanisms governing its ecology and evolution remains obscure. While host genetic distance is a strong predictor of the gut microbiome in large-scale studies and captive settings, its influence has not always been evident at finer taxonomic scales, especially when considering among the recently diverged animals in natural settings. Comparing the gut microbiome of 19 populations of Japanese macaques Macaca fuscata across the Japanese archipelago, we assessed the relative roles of host genetic distance, geographic distance and dietary factors in influencing the macaque gut microbiome. Our results suggested that the macaques may maintain a core gut microbiome, while each population may have acquired some microbes from its specific habitat/diet. Diet-related factors such as season, forest, and reliance on anthropogenic foods played a stronger role in shaping the macaque gut microbiome. Among closely related mammalian hosts, host genetics may have limited effects on the gut microbiome since the hosts generally have smaller physiological differences. This study contributes to our understanding of the relative roles of host phylogeography and dietary factors in shaping the gut microbiome of closely related mammalian hosts.

Gut microbiota composition of Japanese macaques associates with extent of human encroachment.

In recent decades, human-wildlife interaction and associated anthropogenic food provisioning has been increasing and becoming more severe due to fast population growth and urban development. Noting the role of the gut microbiome in host physiology like nutrition and health, it is thus essential to understand how human-wildlife interactions and availability of anthropogenic food in habitats can affect an animal's gut microbiome. This study, therefore, set out to examine the gut microbiota of Japanese macaques (Macaca fuscata) with varying accessibility to anthropogenic food and the possibility of using gut microbiota as indicator for macaques' reliance on anthropogenic food. Using 16S ribosomal RNA gene sequencing, we described the microbial composition of Japanese macaques experiencing different types of human disturbance and anthropogenic food availability-captive, provisioned, crop-raiding, and wild. In terms of alpha diversity, our results showed that observed richness of gut microbiota did not differ significantly between disturbance types but among collection sites, whereas Shannon diversity index differed by both disturbance types and sites. In terms of beta diversity, captive populations harbored the most distinctive gut microbial composition, and had the greatest difference compared with wild populations. Whereas for provisioned and crop-raiding groups, the macaques exhibited intermediate microbiota between wild and captive. We identified several potential bacterial taxa at different taxonomic ranks whose abundance potentially could help in assessing macaques' accessibility to anthropogenic food. This study revealed the flexibility of the gut microbiome of Japanese macaques and provided possible indices based on the gut microbiome profile in assessing macaques' accessibility to/reliance on anthropogenic foods.

Short communication: epidemiological evidence that simian T-lymphotropic virus type 1 in Macaca fuscata has an alternative transmission route to maternal infection.

Serological inspection of Simian T-lymphotropic Virus Type 1 was conducted for a wild colony of Macaca fuscata, which was captured in the middle Honshu, Japan. The increase of positive rate after the juvenile stage with the positive rate reaching 100% (or 35/35) in youngster and adult stages, was observed. This finding suggests that, in contrast with human T-lymphotropic Virus Type 1, horizontal transmission play an important role in increasing prevalence of STLV-1 with age among M. fuscata.

Descriptive epidemiology of fatal respiratory outbreaks and detection of a human-related metapneumovirus in wild chimpanzees (Pan troglodytes) at Mahale Mountains National Park, Western Tanzania.

Over the past several years, acute and fatal respiratory illnesses have occurred in the habituated group of wild chimpanzees at the Mahale Mountains National Park, Tanzania. Common respiratory viruses, such as measles and influenza, have been considered possible causative agents; however, neither of these viruses had been detected. During the fatal respiratory illnesses in 2003, 2005 and 2006, regular observations on affected individuals were recorded. Cause-specific morbidity rates were 98.3, 52.4 and 33.8%, respectively. Mortality rates were 6.9, 3.2 and 4.6%; all deaths were observed in infants 2 months-2 years 9 months of age. Nine other chimpanzees have not been seen since the 2006 outbreak and are presumed dead; hence, morbidity and mortality rates for 2006 may be as high as 47.7 and 18.5%, respectively. During the 2005 and 2006 outbreaks, 12 fecal samples were collected from affected and nonaffected chimpanzees and analyzed for causative agents. Analysis of fecal samples from 2005 suggests the presence of paramyxovirus, and in 2006 a human-related metapneumovirus was detected and identified in an affected chimpanzee whose infant died during the outbreak. Our findings provide preliminary evidence that the causative agent associated with these illnesses is viral and contagious, possibly of human origin; and that, possibly more than one agent may be circulating in the population. We recommend that baseline health data be acquired and food wadge and fecal samples be obtained and bio-banked as early as possible when attempting to habituate new groups of chimpanzees or other great apes. For already habituated populations, disease prevention strategies, ongoing health monitoring programs and reports of diagnostic findings should be an integral part of managing these populations. In addition, descriptive epidemiology should be a major component of disease outbreak investigations.

Food conditions, competitive regime, and female social relationships in Japanese macaques: within-population variation on Yakushima.

Feeding conditions, competitive regime, and female social relationships of Japanese macaques (Macaca fuscata) on Yakushima were compared between the two habitats at two different altitudes (coniferous forest, 1,000-1,200 m and coastal forest, 0-200 m). Fruit availability was higher in the coastal forest. There was no consistent difference in the frequency of agonistic interactions within a group during feeding between the two habitats. The coastal forest evoked stronger inter-group contest competition compared to the coniferous forest as evidenced by a higher inter-group encounter rate and a higher proportion of aggressive encounters to non-aggressive ones. Birth rate was higher in larger groups compared to smaller ones in the coastal forest, but did not differ in the coniferous forest. In spite of these differences in competitive regime, no variation in female social relationships was observed, such as direction and concentration on particular individuals in grooming, linearity in dominance rank, counter-attack, and support of juvenile kin during agonistic interactions. The present results indicate that the female social relationships of Japanese macaques are robust and do not change according to changes in the current environment.

Chimpanzee deaths at Mahale caused by a flu-like disease.

A flu-like disease spread among chimpanzees (Pan troglodytes schweinfurthii) of the M group at Mahale Mountains National Park, Tanzania, from June to July 2006. This epizootic or epidemic killed up to 12 chimpanzees. The obvious evidence of their deaths came from finding the bodies of three infants who had previously shown some symptoms of the disease. At least one of these infants died of pneumonia. In addition, nine chimpanzees were missing after the outbreak. These individuals were assumed to have been killed by this epizootic because most of them had contact with the infected individuals on the last days they were observed. We also found two dead bodies during this period, which were thought to be those of two missing individuals. We confirmed 23 (35.4%) of 65 individuals of the M group showed some symptoms of the disease, although most of them (20/23) did not die. More than half of them (14/23) had kin showing symptoms. Since this epizootic may have been caused by contact with humans, it will be necessary to establish and follow appropriate protocols for researchers, tourists, and park staff to observe chimpanzees, and to explore the mechanism of disease transmission from humans to chimpanzees and among chimpanzees.

Behavioral thermoregulation of wild Japanese macaques: comparisons between two subpopulations.

We studied the behavioral thermoregulation of Japanese macaques in two troops that live in the coniferous (1,000-1,200 m in elevation) and coastal forests (0-200 m in elevation) of Yakushima. Frequency of sunbathing, huddling, and microhabitat selection during inactivity was compared. The difference in mean annual air temperature between the forests was more than 7 degrees C. In both forests, when the weather was clear, macaques spent more time being inactive in the sunshine in winter than in autumn. In winter, they huddled more often when it was clear than when cloudy. Microhabitat selection to stay in the sunshine during winter differed between the two forests. In winter, macaques spent more time inactive in open habitats in the coniferous forest and in the trees in the coastal forest than in autumn, respectively. This difference is related to the lower crown height in the coastal forest and the large open habitats (logged area) available only in the coniferous forest. In winter, skin temperature measured by temperature-sensitive transmitters was 1.32-1.71 degrees C higher when sunbathing, and 0.83-4.75 degrees C higher when huddling than staying in the shade without huddling. In winter, the proportion with which they stayed in the sunshine or huddled in winter did not differ between the two forests, in spite of the difference in air temperature. This suggests that Japanese macaques respond to seasonal changes in air temperature, not the absolute temperature, and that they acclimatize themselves to thermal conditions that require behavioral thermoregulation only during the season when thermoregulation is most costly.

Not only annual food abundance but also fallback food quality determines the Japanese macaque density: evidence from seasonal variations in home range size.

Previous studies on Japanese macaque (Macaca fuscata) densities suggest that both total annual food abundance and the quality of fallback foods in the winter bottleneck period affects density. We reviewed data on the seasonal changes in home range size to explain how both factors affect density. In general, home range was large in summer or autumn and small in spring or winter, indicating that density is determined by the home range size in the seasons before winter. The main foods in these seasons are fruits and seeds. If these foods are not abundant, macaques need to range over a larger area, thus decreasing density. Macaques survive the winter by depending on the fat deposited before winter through eating these high-quality foods. If the food condition in winter is severe and the amount of required fat deposition is large, macaques need a larger home range before winter, and thus density becomes lower.