Mineral acquisition of Japanese macaques: Contents in the foods, digestibility, and sodium-provisioning experiment.

Minerals provide micronutrients that function in various ways in the body, and they are necessary for the survival of animals. In this study, we first compared the mineral content of foods of wild Japanese macaques in lowland Yakushima with that of monkey chow used for many years to feed captive macaques and specifically formulated to obtain good health in captive macaques (National Research Council [NRC] recommendations). Second, we clarified the mineral balance in captive individuals when feeding them monkey chow to clarify the digestibility/bioavailability of the minerals. Third, we investigated the physiological response when we experimentally increased sodium intake. In the lowland of Yakushima, which is in the vicinity (<800 m) of the coast, animals, fungi, and mature leaves had high sodium contents compared with NRC recommendations. The calcium contents of mature leaves and animals were higher than the NRC recommendations. The overall mineral intake in this population was lower than that in the captive animals for calcium, phosphorus, sodium, and iron, while similar for magnesium and higher in potassium. Patterns in the intake and excretion of minerals indicated that excretion was mostly from urine and not from feces, and apparent digestibility was high for sodium. This tendency was opposite for calcium, magnesium, and phosphorus and intermediate for potassium. A sodium-provisioning experiment showed that fecal aldosterone concentration remained low in both control and sodium-provisioning conditions so the macaques do not need reabsorb sodium in the kidneys. Therefore, sodium content in the monkey chow, which is slightly lower than the NRC recommendation, seemed high enough so that the macaques could avoid the need to reabsorb sodium in the kidneys. We advocate similar studies for other primate populations or species to better understand the role of mineral concentrations on food selection and to identify potential mineral deficiencies.

Seasonal responses and host uniqueness of gut microbiome of Japanese macaques in lowland Yakushima.

BACKGROUND: Changes in the gut microbial composition is an important response to cope with the seasonal fluctuations in the environment such as food availability. We examined the bacterial gut microbiome of the wild nonhuman primate, Japanese macaque (Macaca fuscata) in Yakushima over 13 months by noninvasive continuous sampling from three identified adult females. RESULTS: Dietary composition varied considerably over the study period and displayed marked shifts with the seasons. Feeding of leaves, fruits, and invertebrates were their main foods for at least one month. Diet had a significant influence on the gut microbiome. We also confirmed significant effect of host uniqueness in the gut microbiome among the three macaques. Leaf-dominated diet shaped unique gut microbiome structures where the macaques had the highest alpha diversity and their gut microbiome was enriched with Spirochaetes and Tenericutes. Diet-related differences in the putative function were detected, such as a differentially abundant urea cycle during the leaf-feeding season. CONCLUSION: Both diet and host individuality exerted similar amounts of effect on gut microbe community composition. Major bacterial taxa showed a similar response to monthly fluctuations of fruit and invertebrate feeding, which was largely opposite to that of leaf feeding. The main constituents of fruits and invertebrates are both digestible with the enzyme of the host animals, but that of leaves is not available as an energy source without the aid of the fermentation of the gut microbiome.

Evolution of the primate glutamate taste sensor from a nucleotide sensor.

Taste perception plays an essential role in food selection. Umami (savory) tastes are sensed by a taste receptor complex, T1R1/T1R3, that detects proteinogenic amino acids.1 High sensitivity to l-glutamate (l-Glu) is a characteristic of human T1R1/T1R3, but the T1R1/T1R3 of other vertebrates does not consistently show this l-Glu response.1,2 Here, we demonstrate that the l-Glu sensitivity of T1R1/T1R3 is a derived state that has evolved repeatedly in large primates that rely on leaves as protein sources, after their divergence from insectivorous ancestors. Receptor expression experiments show that common amino acid substitutions at ligand binding sites that render T1R1/T1R3 sensitive to l-Glu occur independently at least three times in primate evolution. Meanwhile T1R1/T1R3 senses 5'-ribonucleotides as opposed to l-Glu in several mammalian species, including insectivorous primates. Our chemical analysis reveal that l-Glu is one of the major free amino acids in primate diets and that insects, but not leaves, contain large amounts of free 5'-ribonucleotides. Altering the ligand-binding preference of T1R1/T1R3 from 5'-ribonucleotides to l-Glu might promote leaf consumption, overcoming bitter and aversive tastes. Altogether, our results provide insight into the foraging ecology of a diverse mammalian radiation and help reveal how evolution of sensory genes facilitates invasion of new ecological niches.

Stomach and colonic microbiome of wild Japanese macaques.

Within the gastrointestinal tract, the physiochemical microenvironments are highly diversified among the different stages of food digestion. Accordingly, gut microbiome composition and function vary at different gut sites. In this study, we examine and compare the compositional and functional potential between the stomach and colonic microbiome of wild Japanese macaques (Macaca fuscata yakui) living in the evergreen forest of Yakushima Island. We find a significantly lower microbial diversity in the stomach than in the colon, possibly due to the stomach's acidic and aerobic environment, which is suboptimal for microbial survival. According to past studies, the microbial taxa enriched in the stomach are aero- and acid-tolerant. By functional prediction through PICRUSt2, we reveal that the stomach microbiome is more enriched in pathways relating to the metabolism of simple sugars. On the contrary, the colonic microbiota is more enriched with fiber-degrading microbes, such as those from Lachnospiracea, Ruminococcaceae, and Prevotella. Our study shows a clear difference in the microbiome between the stomach and colon of Japanese macaques in both composition and function. This study provides a preliminary look at the alpha diversity and taxonomic composition within the stomach microbiome of Japanese macaques, a hindgut-fermenting nonhuman primate.

Behavioral responses of Japanese macaques to playback-simulated intergroup encounters.

Group-living animals gain fitness benefits from intergroup aggression, but also incur costs. Advertisement behaviors, such as long-distance calls and scent marking, help animals avoid disadvantageous, or less rewarding, fights. However, it remains unclear how species that lack advertisement behaviors respond to auditory information from other groups. We hypothesized that such species use auditory information prior to visual contact with the opponent group to determine its relative resource holding potential. Here, we aimed to identify the behavioral responses of Japanese macaques to simulated intergroup encounters. We conducted a vocal playback experiment and behavioral observations of 11 adult males and females from two groups intermittently from October 2015 to June 2017. In response to vocalizations of other groups, the macaques stopped feeding, decreased contact calling, and increased visual scanning, which could enable them to make timely and accurate decisions as to whether to fight or flee. The spatial cohesion of the group did not change. These results partly support our hypothesis and suggest that the onset of increased vigilance to opponents is prior to visual contact with them. The present study highlights the importance of investigating early phases of intergroup encounters in species lacking advertisement behaviors to obtain new insights on intergroup conflicts in animals.

Seasonal variation in energy balance of wild Japanese macaques (Macaca fucata yakui) in a warm-temperate forest: a preliminary assessment in the coastal forest of Yakushima.

Food scarcity is a major challenge for primates living in temperate forests, where food availability varies markedly among seasons. In Japanese macaques, which are exclusively distributed in temperate zones, the fat accumulation ability has been highlighted as an adaptation for survival during the lean season and for reproductive success. However, the knowledge of energetic strategies of Japanese macaques has been mainly derived from data on cool-temperate forests, where fallback foods comprise winter buds and bark. Data on Japanese macaques in warm-temperate forests where fallback foods comprise mature leaves are still lacking. We aimed to identify seasonal variations in energy balance and the relative importance of ingestion rates (dry matter intake per feeding time), energy content of the food, and feeding time in energy intake of Japanese macaques in the coastal forest of Yakushima. We estimated energy balance of 6-12 adult females from October 2012 to October 2013. We estimated energy intake based on the data on feeding behavior and energy content of the diet and calculated energy expenditure based on the previously established relationship between body mass and total energy expenditure. We also quantified urinary C-peptide, which is a non-invasive biomarker of energetic conditions. We demonstrated that energy balance was more positive in the fruit/seed-feeding period than in the mature-leaf-feeding and fruit/fungi-feeding periods and that ingestion rates were the most important component of energy intake. The present study suggests that the fat accumulation ability is an essential adaptation in Japanese macaques even in warm-temperate forests.

Variation in chewing efficiency of Yakushima Japanese macaque (Macaca fuscata yakui).

OBJECTIVES: Chewing efficiency plays an important role in the survival and distribution of primates. Yet, little is known about the intra-specific variation of chewing efficiency. The purpose of this study is to report the pattern of seasonal and regional variation in chewing efficiency among Yakushima Japanese macaques (Macaca fuscata yakui). MATERIALS AND METHODS: Fecal samples of Yakushima Japanese macaques were collected from lowland, highland and summit areas in Yakushima between July 2015 and March 2016 (n = 236). Using sieving analysis, we compared fecal particle size (dMEAN) and proportion of finest particles p(0) between different geographical areas and seasons. RESULTS: Seasonally, in the lowland zone, there was a non-significant decrease in dMEAN during spring, while p(0) was significantly higher during summer than it was during winter and spring. Regionally, dMEAN was higher in the summit zone than it was in other areas during autumn, while p(0) was also higher in the summit zone. CONCLUSIONS: While seasonal variation in dMEAN can be explained by the reported difference in the proportions of food categories in diet between seasons, its influence is mitigated, possibly by the selective feeding of less mechanically challenging parts in each category. Regional variation in dMEAN and p(0) may be the results of bamboo consumption in this area. Combining our data with studies that focus on seasonal and regional variations of food properties or gut microbes might provide a better understanding of the relation between diet, chewing and digestion in Yakushima macaques.

Behavioral responses to changes in group size and composition: a case study on grooming behavior of female Japanese macaques (Macaca fuscata yakui).

Primates flexibly change their grooming behavior depending on group size and composition to maintain social relationships among group members. However, how drastic social changes influence their grooming behavior remains unclear. We observed the grooming behavior of adult female Japanese macaques in two groups temporarily formed as one-female groups from multi-female groups and compared their behaviors between the multi-female and one-female periods. Adult females more frequently performed grooming with both their relatives and unrelated juveniles during the one-female period when other adult females were unavailable as alternatives to their absent familiar partners. The increased grooming time and diversity of grooming partners might alleviate the short-term stress caused by the loss of grooming partners and reduce social instability or mitigate the long-term stress due to disadvantages in intergroup conflicts. Our study provides rare evidence on the flexibility in grooming behavior of primates and encourages accumulating case reports for understanding behavioral responses of primates to drastic social changes.

Within-Population Variations in Home Range Use and Food Patch Use of Japanese Macaques: A Perspective of Intergroup Hostility.

Behavioral mechanisms of intergroup feeding competition remain unclear, despite its importance as a benefit of group living. Japanese macaques in the coastal and highland forests of Yakushima, Japan, are ideal study subjects because the intensity of intergroup feeding competition differs without phylogenetic effects. We aimed to test whether macaques modify home range use and food patch use in response to the location-specific risk of intergroup encounters. Using behavioral data from 3 groups, we examined the border avoidance and the effects of food patch location on food patch use. All 3 groups used the border less frequently than expected from its area. In the coastal forest characterized by frequent intergroup aggression, the smaller subordinate group, not the larger dominant group, increased the number of co-feeding individuals along the border. This response might reduce the potential costs of intergroup aggression. Feeding duration in one patch, visual scanning, and co-feeding with adult males did not depend on food patch location for the 2 groups. In contrast, the highland group did not modify food patch use along the border owing to the low risk of intergroup encounters. Our results highlight the importance of intergroup hostility as a social factor affecting animal behavior.

Seasonal variation of energy expenditure in Japanese macaques (Macaca fuscata).

Animals living in seasonal environments must adapt to a wide variation of temperature changes which requires flexible adjustments of time budget and metabolic processes for efficient thermoregulation. The Japanese macaque (Macaca fuscata) is one of only a handful of nonhuman primate species that experience seasonal climates over a wide temperature range. We used behavior observations, accelerometer sensors and the doubly-labelled water (DLW) method to measure activity and total daily energy expenditure (TDEE) of M. fuscata housed in captivity but exposed to natural seasonal variations at day lengths ranging from 10 to 12 h and temperature ranging from 0° to 32°C. Although overall activity was significantly lower in winter compared to summer and autumn, we found no effect of temperature on day-time activity. However nocturnal inactivity and mean length of sleeping bouts significantly increased along a gradient of decreasing temperatures from summer through winter, suggesting the importance of adaptive behavioral thermoregulation in this species. Energy expenditure that was unaccounted for by Basal Metabolic Rate (BMR) and physical activity i.e. expended through diet-induced thermogenesis or thermoregulation was between 14% and 32%. This residual energy expenditure differed between summer/autumn and winter and was relatively consistent across individuals (approximately 5-8% higher in winter). The percentage of body fat and residual energy expenditure were negatively correlated, supporting that fat storage was higher when less energy was required for thermoregulation. Our results suggest that physiological mechanisms like behavioral and autonomic thermoregulation enable M. fuscata to adapt to wide fluctuations in environmental conditions which provide insights into the evolutionary adaptations of nonhuman primates in seasonal climate.

Improving the standards for gut microbiome analysis of fecal samples: insights from the field biology of Japanese macaques on Yakushima Island.

Fecal DNA-based 16S ribosomal RNA (rRNA) gene sequencing using next-generation sequencers allows us to understand the dynamic gut microbiome adaptation of animals to their specific habitats. Conventional techniques of fecal microbiome analysis have been developed within the broad contexts defined by human biology; hence, many of these techniques are not immediately applicable to wild nonhuman primates. In order to establish a standard experimental protocol for the analysis of the gut microbiomes of wild animals, we selected the Japanese macaques (Macaca fuscata yakui) on Yakushima Island. We tested different protocols for each stage of fecal sample processing: storage, DNA extraction, and choice of the sequencing region in the bacterial 16S rRNA gene. We also analyzed the gut microbiome of captive Japanese macaques as the control. The comparison of samples obtained from identical macaques but subjected to different protocols showed that the tested storage methods (RNAlater and lysis buffer) produced effectively the same composition of bacterial operational taxonomic units (OTUs) as the standard frozen storage method, although the relative abundance of each OTU was quantitatively affected. Taxonomic assignment of the detected bacterial groups was also significantly affected by the region being sequenced, indicating that sequencing regions and the corresponding polymerase chain reaction (PCR) primer pairs for the 16S rRNA gene should be carefully selected. This study improves the current standard methods for microbiome analysis in wild nonhuman primates. Japanese macaques were shown to be a suitable model for understanding microbiome adaptation to various environments.

Comparison of energy balance between two different-sized groups of Japanese macaques (Macaca fuscata yakui).

Quantifying the energy balance is essential for testing socio-ecological models. To reveal costs and benefits of group living in Japanese macaques from the perspective of feeding competition, Kurihara and Hanya (Am J Primatol 77:986-1000, 2015) previously compared feeding behavior between two different-sized groups of macaques (larger group 30-35 individuals; smaller group 13-15 individuals) in the coastal forest of Yakushima, Japan. The results suggested that the larger group exhibited greater feeding effort because of intragroup scramble competition and that the smaller group suffered from higher travel costs, possibly owing to intergroup contest competition. However, it remained unclear whether the behavioral differences affected their energy budgets. The present study examined energetic consequences of the different feeding behaviors in the two groups. Using behavioral data from 10 to 13 adult females and nutritional composition of food items, we compared ingestion rates, energetic/nutritional content of diet, and energy budgets between the two groups. Ingestion rates and energetic/nutritional content of diet did not differ between the two groups. Despite the higher feeding effort of the larger group, energy intake did not differ between the two groups. Energy expenditure did not differ between the two groups because higher travel costs were negated by lower feeding effort in the smaller group. Consequently, the energy balance did not differ between the two groups. We demonstrated that the behavioral measures of feeding competition were not translated into their energetic condition; moreover, our findings re-emphasize the importance of quantifying behavioral and fitness measures for interpreting variation in feeding behavior properly.

Low-ranking female Japanese macaques make efforts for social grooming.

Grooming is essential to build social relationships in primates. Its importance is universal among animals from different ranks; however, rank-related differences in feeding patterns can lead to conflicts between feeding and grooming in low-ranking animals. Unifying the effects of dominance rank on feeding and grooming behaviors contributes to revealing the importance of grooming. Here, I tested whether the grooming behavior of low-ranking females were similar to that of high-ranking females despite differences in their feeding patterns. I followed 9 Japanese macaques Macaca fuscata fuscata adult females from the Arashiyama group, and analyzed the feeding patterns and grooming behaviors of low- and high-ranking females. Low-ranking females fed on natural foods away from the provisioning site, whereas high-ranking females obtained more provisioned food at the site. Due to these differences in feeding patterns, low-ranking females spent less time grooming than high-ranking females. However, both low- and high-ranking females performed grooming around the provisioning site, which was linked to the number of neighboring individuals for low-ranking females and feeding on provisioned foods at the site for high-ranking females. The similarity in grooming area led to a range and diversity of grooming partners that did not differ with rank. Thus, low-ranking females can obtain small amounts of provisioned foods and perform grooming with as many partners around the provisioning site as high-ranking females. These results highlight the efforts made by low-ranking females to perform grooming and suggest the importance of grooming behavior in group-living primates.

Comparison of feeding behavior between two different-sized groups of Japanese macaques (Macaca fuscata yakui).

Group-living animals face intragroup scramble and intergroup contest competitions. Many studies have shown that larger groups bear the costs of intragroup scramble competition, which negatively affects the reproductive success of females. Unlike most primate species, Japanese macaques in the Yakushima coastal forest show increased reproductive success with group size. However, it remains unclear how group size affects the behavior of macaques. The present study examined the effects of group size on the feeding behavior of Japanese macaques in the Yakushima coastal forest. We investigated 9-13 adult females from two different-sized groups via focal animal sampling during October 2012-August 2013. We compared the feeding behavior, including patch use, between the two groups. The larger group had a larger home range and spent more time feeding, especially on mature leaves. This suggests that intragroup feeding competition should be more intense in the larger group than in the smaller group. The feeding of mature leaves might enable the larger group to increase the number of co-feeding individuals. Contrary to the predictions that the larger group travels longer distances and spends more time moving, the smaller group traveled longer distances, and spent more time moving, although the number of visited patches did not differ between the two groups. The immediate consequences of the loss of inter-group encounters could accumulate as daily travel costs, considering that group size is associated with inter-group dominance and that intergroup aggressive encounters occur frequently in the Yakushima coastal forest. This suggests that the smaller group has increased travel costs as a result of intergroup contest competition, which leads to decline in reproductive success. Am. J. Primatol. 77:986-1000, 2015. © 2015 Wiley Periodicals, Inc.

Accelerometry-based gait analysis and its application to Parkinson's disease assessment--part 1: detection of stride event.

Gait analysis is widely recognized as a promising tool for obtaining objective information on the walking behavior of Parkinson's disease (PD) patients. It is especially useful in clinical practices if gait properties can be captured with minimal instrumentation that does not interfere with the subject's usual behavioral pattern under ambulatory conditions. In this study, we propose a new gait analysis system based on a trunk-mounted acceleration sensor and automatic gait detection algorithm. The algorithm identifies the acceleration signal with high intensity, periodicity, and biphasicity as a possible gait sequence, from which gait peaks due to stride events are extracted by utilizing the cross-correlation and anisotropy properties of the signal. A total of 11 healthy subjects and 12 PD patients were tested to evaluate the performance of the algorithm. The result indicates that gait peaks can be detected with an accuracy of more than 94%. The proposed method may serve as a practical component in the accelerometry-based assessment of daily gait characteristics.

Accelerometry-based gait analysis and its application to Parkinson's disease assessment- part 2: a new measure for quantifying walking behavior.

Gait analysis is a valuable tool for obtaining quantitative information on motor deficits in Parkinson's disease (PD). Since the characteristic gait patterns of PD patients may not be fully identified by brief examination in a clinic, long-term, and unobtrusive monitoring of their activities is essential, especially in a nonclinical setting. This paper describes a single accelerometer-based gait analysis system for the assessment of ambulatory gait properties. Acceleration data were recorded continuously for up to 24 h from normal and PD subjects, from which gait peaks were picked out and the relationship between gait cycle and vertical gait acceleration was evaluated. By fitting a model equation to the relationships, a quantitative index was obtained for characterizing the subjects' walking behavior. The averaged index for PD patients with gait disorder was statistically smaller than the value for normal subjects. The proposed method could be used to evaluate daily gait characteristics and thus contribute to a more refined diagnosis and treatment of the disease.

Development of unconstrained heartbeat and respiration measurement system with pneumatic flow.

The management of health through daily monitoring of heartbeat and respiration signals is of major importance for early diagnosis to prevent diseases of the respiratory and circulatory system. However, such daily health monitoring is possible only if the monitoring system is physically and psychologically noninvasive. In this paper, an unconstrained method of measuring heartbeat and respiration signals, by using a thermistor to measure the air flows from the air mattress to an air tube accompanying the subject's heartbeat and respiration, is proposed. The SN ratio with interference by opening and closing of a door as environmental noise was compared with that obtained by the conventional condenser microphone method. As a result, the SN ratios with the condenser microphone method were 26.6 ± 4.2 dB for heartbeat and 27.8 ± 3.0 dB for respiration, whereas with the proposed method they were 34.9 ± 3.1 dB and 42.1 ± 2.5 dB, respectively.

Unconstrained estimation method of delta-wave percentage included in EEG of sleeping subjects.

This paper describes an unconstrained pneumatic method of estimating the δ-wave activity of the brain from the heartbeat signal. Based on experiments showing that transinformation of the heartbeat signal corrupted by body movement was correlated with the δ-wave activity, we developed a method of estimating the percentage of the δ-wave included in the EEG from the transinformation. The comb filtering technique was used to obtain accurate transinformation. We applied the proposed method to young normal subjects to evaluate the method. As a result, the correlation between the δ -wave included in the EEG and the transinformation was 0.727 and the average error of the estimates of δ-wave percentage was 14.9%. The δ-wave activity and heartbeat activity were shown to be quantitatively related. This suggests that sleep depth can be estimated from the δ -wave percentage estimated by unconstrained measurement of the heartbeat signal of young normal subjects.

Sleep-states-transition model by body movement and estimation of sleep-stage-appearance probabilities by Kalman filter.

The judgment standards of R-K method include ambiguities and are thus compensated by subjective interpretations of sleep-stage scorers. This paper presents a novel method to compensate uncertainties in judgments by the subjective interpretations by the sleep-model estimation approach and by describing the judgments in probabilistic terms. Kalman filter based on the two sleep models with no body movement and with body movement was designed. Sleep stages judged by three different scorers were rejudged by the filter. The two sleep models were stochastically estimated from biosignals from 15 nights' data and the rejudged scores by the filter were evaluated by the data from 5 nights. The average values of kappa statistics, which show the degree of agreement, were 0.85, 0.89, and 0.81, respectively, for the original sleep stages. Because the new method provides probabilities on how surely the sleep belongs to each sleep stage, we were able to determine the most, second most, and third most probable sleep stage. The kappa statistics between the most probable sleep stages were improved to 0.90, 0.93, and 0.84, respectively. Those of sleep stages determined from the most and second most probable were 0.92, 0.94, and 0.89 and those from the most, second most, and third most probable were 0.95, 0.97, and 0.92. The sleep stages estimated by the filter are expressed by probabilistic manner, which are more reasonable in expression than those given by deterministic manner. The expression could compensate the uncertainties in each judgments and thus were more accurate than the direct judgments.