Biology subjects

Matsuda, I.

Publications and source records attributed to Matsuda, I..

At least 19 recordsLinked to original sources

bioRxiv2026

Long-term Population Dynamics and Conservation of Proboscis Monkeys (Nasalis larvatus) in the Lower Kinabatangan, Sabah, Malaysia

Long-term ecological monitoring is essential for evaluating the effectiveness of conservation actions for long-lived tropical primates, yet few studies have integrated repeated population censuses with habitat-change analyses. We evaluated long-term population and habitat dynamics of the endangered proboscis monkey (Nasalis larvatus) in the Lower Kinabatangan, Sabah, Malaysian Borneo, by integrating a landscape-wide population survey conducted in 2025 with previous surveys from 2005 and 2014, long-term monitoring at three representative sites, and spatial analyses of land-use and land-cover change. Standardized late-afternoon boat-based surveys covering approximately 223 km of the Kinabatangan River and its tributaries recorded an estimated 2,420 individuals in 174 social groups, representing an increase of approximately 66% and 72% respectively compared with the 2005 survey. Group sizes (number of individuals per social group) remained largely unchanged despite the overall increase in population size. Long-term monitoring at three representative sites indicated stable population trajectories throughout the study period. Habitat analyses further revealed an increase in natural vegetation and limited conversion of forest to oil palm within protected areas between 2005 and 2025. Together, these independent lines of evidence indicate that the Lower Kinabatangan proboscis monkey population has recovered while maintaining overall demographic stability under long-term habitat protection. Nevertheless, substantial areas of suitable habitat remain outside the protected-area network, highlighting opportunities for additional habitat restoration and improved landscape connectivity. Our findings demonstrate the value of integrating long-term ecological monitoring with landscape-scale habitat assessment to inform adaptive conservation management in fragmented tropical landscapes.

ecology↗

bioRxiv2026

Spatial patterns of mosquito communities and monkey malaria vectors in a tropical riverine forest in Sabah, Malaysian Borneo

Understanding how vector ecology intersects with host behaviour is essential for predicting zoonotic disease risk in tropical ecosystems. We conducted a two-year field study (November 2016-October 2018) in a riverine forest in Sabah, Malaysian Borneo, to characterize mosquito communities and the spatial distribution of potential simian-malaria vectors. Mosquitoes were sampled on 44 nights using CO{square}-baited light traps repeatedly deployed along a 500 m transect at three distances from the river (0, 250, 500 m) and two vertical strata (ground and canopy), yielding 244 trap collections across repeated sampling nights. In total, 9,928 mosquitoes were collected, dominated by Culex spp. (9,079; 91.4%), whereas Anopheles spp. were rare (153; 1.5%); most remaining specimens were unidentified to genus, and species-level identification was limited primarily to Anopheles. Nevertheless, female Anopheles (n=57) were more frequently detected near the river and less commonly at intermediate distance, and tended to be captured more often in ground traps. Zero-inflated negative binomial GLMMs based on the full mosquito dataset indicated significant effects of river distance and height on mosquito abundance, while night-time temperature and humidity showed no detectable effects. The zero-inflated structure of the data further suggested that many zero captures reflected true absence rather than sampling variability. The Anopheles assemblage was dominated by An. balabacensis, and molecular screening of 57 females detected simian Plasmodium DNA in two individuals. Overall, these findings suggest that river-edge habitats may represent localized areas where vectors persist and where primates and human activities overlap, creating repeated opportunities for host-vector contact even when vector densities are low.

ecology↗

bioRxiv2026

Helminth infection dynamics in rehabilitating Javan slow lorises are driven by time since deworming rather than host traits

Wildlife rehabilitation plays a central role in the conservation of threatened primates, yet parasite dynamics during captivity are rarely reported, particularly in relation to release readiness. We investigated gastrointestinal helminth infection patterns in rehabilitating Javan slow lorises (Nycticebus javanicus), a Critically Endangered species heavily impacted by the illegal wildlife trade. Using repeated fecal sampling (147 samples from 19 adults) and Bayesian mixed-effects models, we examined parasite richness, Shannon diversity, infection probability, and egg-shedding intensity in relation to release readiness status, sex, housing condition, and time since anthelmintic treatment. Four nematode taxa identifiable through egg morphology were detected: Strongyloides spp., strongylids, oxyurids, and Trichuris spp.. Parasite richness and Shannon diversity showed no credible associations with release readiness or other host and management variables. In contrast, infection probability for Strongyloides spp. and strongylids increased with time since deworming, and Strongyloides egg counts exhibited a similar temporal pattern, consistent with post-treatment reinfection dynamics. Release readiness did not predict detection probability or parasite intensity for any parasite group, despite marked differences in captivity duration and health history between individuals deemed ready for release or not. These findings indicate that gastrointestinal helminth dynamics in rehabilitating slow lorises are driven primarily by treatment-related temporal processes and individual-level heterogeneity rather than coarse host classification. They also highlight the need for longitudinal parasite monitoring and for future work evaluating how infection dynamics, management interventions, and host health relate to rehabilitation and translocation outcomes..

ecology↗

bioRxiv2026

Oral and gut microbiomes reveal latent physiological constraints on release readiness in rehabilitating Javan slow lorises

Illegal wildlife trade and habitat degradation displace thousands of animals annually in Southeast Asia, with many confiscated primates housed in rehabilitation centers that increasingly function as long-term holding environments. In slow lorises, dental clipping associated with the pet trade may generate persistent disruption along the oral-gut axis, potentially undermining physiological readiness for release in ways not captured by conventional screening. Here, we evaluated whether microbiome structure provides an integrative marker of release readiness in rehabilitating Javan slow lorises (Nycticebus javanicus). From June to October 2024, we collected fecal (n = 26) and saliva (n = 18) samples from 19 adults housed at YIARI, including 10 release candidates and 9 non-candidates classified primarily based on tooth loss, medical history, and possibility of release. Bacterial communities were characterized using 16S rRNA (V3-V4) amplicon sequencing, with alpha and beta diversity, taxonomic enrichment (LEfSe), and predicted functional profiles (PICRUSt2) assessed. Microbiome composition was strongly compartmentalized by body site, with higher alpha diversity in the gut. Release candidacy was associated with modest gut compositional differences, whereas oral microbiomes showed pronounced divergence between candidates and non-candidates. Non-candidates were enriched in dysbiosis-associated taxa and degradation-oriented functional pathways, while candidates showed enrichment of biosynthetic and central energy metabolism pathways. Gut microbiome structure was stable across pre-release and soft-release phases. These findings indicate that oral and gut microbiomes represent distinct physiological niches and that persistent oral microbiome alteration is a sensitive marker of long-term dental perturbation. Integrating microbiome-informed metrics may improve multidimensional assessment of release readiness.

microbiology↗

bioRxiv2025

Activity Budgets and Boldness as Potential Predictors of Release Readiness in Rehabilitating Javan Slow Lorises

Rehabilitation centers are central to the conservation of Javan slow lorises (Nycticebus javanicus) by providing care for individuals confiscated from trade and preparing them for potential release. To evaluate behavioral readiness for reintroduction, we quantified activity budgets and boldness in 10 adult N. javanicus (7 females and 3 males) housed at a rehabilitation facility in West Java, Indonesia, from May to September 2024. Locomotion dominated activity budgets (57.14% {+/-} 24.86%), followed by resting (23.51% {+/-} 16.61%), with low rates of stereotypy (4.36% {+/-} 13.48%) and grooming (2.33% {+/-} 5.28%). Boldness tests using six novel object types revealed strong stimulus dependence: predator models suppressed approach, while enrichment and neutral objects encouraged exploration. Sex, housing conditions, and rehabilitation duration did not predict boldness, indicating inter-individual differences in responses to novelty. Principal component analysis identified an integrated bold-exploratory activity axis, suggesting that activity budgets and boldness covary as part of a behavioral syndrome rather than independent traits. Together, these results indicate that combined activity and personality metrics provide complementary indicators of behavioral welfare and release readiness, with potential to improve pre-release assessment and site matching for this critically endangered primate.

animal behavior and cognition↗

bioRxiv2025

Impact of Group Size and Habitat Disturbance on Parasitic Infection in Free-ranging Proboscis Monkeys

Group-living primates experience the benefits and costs associated with sociality, including an elevated risk of parasite transmission. However, the relative influence of group type (i.e., social structure), group size, and habitat disturbance on parasitic infection remains unclear, particularly in Southeast Asian primates. In this study, the abundance of intestinal parasites in proboscis monkeys (Nasalis larvatus) inhabiting a riverine forest along the Menanggul River, Sabah, Malaysian Borneo, was investigated. Fecal samples (n = 160) were collected from one-male-multifemale and all-male groups in areas with varying levels of anthropogenic disturbance, with efforts made to ensure that each sample originated from a different individual. In addition, the effects of group type, group size, and sampling location on parasite abundance were evaluated using fecal egg counts and Bayesian models. Three dominant parasite species groups (Trichuris sp., Strongyloides fuelleborni, and Oesophagostomum aculeatum) with an overall infection prevalence of 81.25% were identified. Results showed that group type did not significantly affect parasite abundance. However, group size showed a positive correlation with the abundance of Trichuris sp. and a negative correlation with S. fuelleborni and O. aculeatum. In addition, our models revealed that the infection load of Trichuris sp. decreased with increasing distance from the river mouth, which was used as a proxy for a disturbance gradient, whereas O. aculeatum exhibited higher infection load at greater distances, indicating lower prevalence in more disturbed downstream areas. Thus, parasite abundance in proboscis monkeys may be shaped by social and environmental factors, with taxa-specific responses likely reflecting differences in environmental persistence and transmission ecology.

ecology↗

bioRxiv2025

Analysis of individual identification and age-class classification of wild macaque vocalizations without pitch- and formant-based acoustic parameter measurements

In recent years, deep learning has achieved high performance in bioacoustic classification tasks by leveraging automatically processed acoustic features for large datasets. However, few performance evaluations of automatically processed acoustic features have been conducted on small-scale data because deep learning requires large datasets. To test whether mel spectrograms (an automatically processed acoustic features) are effective for classifying relatively small acoustic data, we evaluated the performance of two classification machines (random forest and support vector machine) using mel-spectrograms of 651 coo calls of six wild female Japanese macaques on two tasks: 1) individual identification and 2) age-class classification between younger (<10 yrs) and the older animals (>20 yrs). For the individual identification task, the mean balanced accuracy was 0.81 for random forest and 0.82 for support vector machine. For the age-class classification task, the mean balanced accuracy was 0.91 for random forest and 0.93 for support vector machine. Considering that of all the calls were recorded in the wild, methods using automatically processed acoustic features, such as mel spectrogram, are effective in classifying small acoustic data for the individual identification task. The high performance in the age-class classification task might be attributable to the potential of mel spectrograms to capture the characteristics of older individuals (e.g. harshness).

animal behavior and cognition↗

bioRxiv2023

Gut microbial community in proboscis monkeys: implications for effects of geographical and social factors

Recent technological advances have enabled comprehensive analyses of the previously uncharacterized microbial community in the gastrointestinal tracts of numerous animal species; however, the gut microbiota of several species, such as the endangered proboscis monkey (Nasalis larvatus) examined in this study, remains poorly understood. Our study sought to establish the first comprehensive data on the gut microbiota of free-ranging foregut-fermenting proboscis monkeys and to determine how their microbiota are affected locally by environmental factor, i.e. geographical distance, and social factor, i.e. number of adult females within harem groups and number of adults and subadults within non-harem groups, in a riparian forest in Sabah, Malaysian Borneo. Using 16S rRNA gene sequencing of 264 faecal samples collected from free-ranging proboscis monkeys, we demonstrated the trend that their microbial community composition is not particularly distinctive compared to other foregut and hindgut fermenting primates. The microbial alpha diversity was higher in larger groups and individuals inhabiting diverse vegetation (i.e. presumed to have a diverse diet). For microbial beta diversity, some measures were significant, showing higher values with larger geographical distances between samples. These results suggest that social factors such as increased interindividual interactions, which can occur with larger groups, as well as physical distances between individuals or differences in dietary patterns, may affect the gut microbial communities.

microbiology↗

bioRxiv2023

The multilevel society of proboscis monkeys with a possible patrilineal basis

Multilevel societies (MLS), which are characterized by two or more levels of social organization, are among the most complex primate social systems. MLS have only been recorded in a limited number of primates, including humans. The aim of this study was to investigate whether proboscis monkeys (Nasalis larvatus) form MLS in Sabah, Malaysia, and to genetically characterize their dispersal patterns. Association data were obtained through direct observation (35 months) and kinship data through genetic analysis, based on feces collected from [~]200 individuals. The results strongly suggest that proboscis monkeys exhibit a form of MLS, with several core reproductive units and a bachelor group woven together into a higher-level band. Genetic analysis revealed that the females migrated randomly over short and long distances; however, the males tended to migrate relatively shorter distances than females. Furthermore, male-male dyads showed a slightly higher average relatedness than female-female dyads. Combined with the results of direct observations, we conclude that proboscis monkeys form a MLS with at least two layers and a patrilineal basis. Since patrilineal MLS have been identified as an important step in the evolution of human societies, their convergent appearance in proboscis monkeys may help us understand of the drivers of human social evolution. Significance StatementThe aim of this study was to determine the social organization of proboscis monkeys by direct observation and genetic analysis. The results revealed that their social system exhibited a form of multilevel society with a possible patrilineal basis. Since humans exhibit a similar constellation of social features, proboscis monkeys may offer insightful clues about human social evolution.

animal behavior and cognition↗

bioRxiv2021

Effects of short-term isolation on social animals' behavior: an experimental case study of Japanese macaque

One of the goals in animal socioecology is to understand the functions and dynamics of group living. While observations of free-ranging animals are a crucial source of information, an experimental investigation that manipulates the size or composition, or both, of animal groups in captivity can also bring complementary contributions to the research inquiry. When paired with an automatic data collection by biologging technology, experimental studies on captive animals also allow for big data analyses based on recent machine learning techniques. As an initial exploration of this research paradigm, the present study inquired to what extent isolation of captive Japanese macaques (Macaca fuscata) changed their movement patterns. Using three-dimensional location trajectories of the macaques that were systematically collected via Bluetooth Low Energy beacons and a deep neural network, we estimated the identifiability of whether a macaque was behaving in isolation or in group. We found that the neural network identified the isolation vs. in-group conditions with more than 90% accuracy from a five-minute location trajectory, suggesting that the isolation caused notable changes from the canonical group-living behaviors. In addition, the isolation made each individual more identifiable from one another based on their location trajectories.

animal behavior and cognition↗

bioRxiv2021

Dietary habits of free-ranging banded langur (Presbytis femoralis) in a secondary-human modified forest in Johor, Malaysia

Banded langurs, Presbytis femoralis, are distributed in southern Peninsular Malaysia, i.e., Johor and its borders including Singapore. It has been estimated that there are only < 250 mature individuals of P. femoralis in Malaysia and Singapore, and it is currently assessed as Critically Endangered. The dietary information of P. femoralis and even other closely related species has rarely been reported. This study, therefore, aimed to describe their dietary habits and discuss interaction between their feeding behaviour and its surrounding. This study was conducted from February to November 2018, with 15 sampling days each month. We collected a total of 186 sighting hours, using a scan sampling method with 10-min intervals, on a five-langur focal group. We have identified 29 species with 47 items consumed by the banded langur, mostly young leaves (51 %) followed by fruits (45 %), and flowers (3.8 %). The study group spent slightly more time consuming non-cultivated plants but relied on cultivated plants for the fruits. Over 75% of fruit feeding involved consuming cultivar plants; in most cases (73%), they ate only the pulp, not the seeds. Since the cultivated plants was planted in human settlement, there is an urgent need to implement conservation measures to untangle the human-langur conflicts for instance, reforestation of a buffer region using non-cultivated plants. There is a potential for building upon our new findings with more detailed investigations, such as more extensive ecological factors influencing the dietary adaptation which would be necessary to support conservation efforts and management decisions of this species.

ecology↗

bioRxiv2021

Apparent digestibility of captive colobines in relation to stomach types with special reference to fibre digestion

Colobine monkeys are known for the anatomical complexity of their stomachs, making them distinct within the primate order. Amongst foregut fermenters, they appear peculiar because of the occurrence of two different stomach types, having either three ( tripartite) or four ( quadripartite, adding the praesaccus) chambers. The functional differences between tri and quadripartite stomachs largely remain to be explained. In this study, we aim to compare the apparent digestibility (aD) in tripartite and quadripartite colobines. Hence, we measured the aD in two colobine species, Nasalis larvatus (quadripartite) and Trachypithecus cristatus (tripartite), in two zoos. We also included existing colobine literature data on the aD and analysed whether the aD of fibre components is different between the stomach types to test the hypothesis of whether quadripartite colobines show higher aD of fibre components than tripartite colobines did. Our captive N. larvatus specimen had a more distinctively varying nutrient intake across seasons with a larger seasonal variation in aD than that of a pair of T. cristatus, which mostly consumed commercial foods with a lower proportion of browse and less seasonal variation. We observed higher aD of dry matter (DM), neutral detergent fibre (NDF) and acid detergent fibre (ADF) in the N. larvatus specimen, suggesting a higher gut capacity of N. larvatus provided by the additional praesaccus forestomach chamber. Based on the analysis of literature data for aD, we also found that quadripartite species achieved higher fibre digestibility at similar dietary fibre levels compared with tripartite species, supporting the hypothesis that the additional gut capacity offered by the praesaccus facilitates a longer retention and hence more thorough microbial fermentation of plant fibre.

zoology↗

bioRxiv2020

Population dynamics and ranging behaviors of provisioned silvered langur (Trachypithecus cristatus) in Peninsular Malaysia

Tourists are attracted to the Bukit Melawati Kuala Selangor (BMKS) of Peninsular Malaysia, a small hill park, both for its status as a historical site and the free-ranging silvered langurs (Trachypithecus cristatus) that come for provisioning. We assessed the population trends and group sizes of T. cristatus over 10 years in the BMKS and examined their ranging patterns. Comparisons of observed populations between 2005 (190 individuals) and 2017 (193 individuals) revealed the stable demography and group sizes of the six T. cristatus groups in the BMKS. Based on a total of 185 location points of the six groups in 2017, their mean ranging area was 3.6 ha with a range of 0.86 to 6.93 ha with extensive spatial overlap. We also found a significant positive relationship between the six groups ranges and group sizes in 2017. Additionally, qualitative ecological comparisons with a previous study on T. cristatus in 1965 (before provisioning) suggest that the artificial food supply in the study area could modify the population dynamics and socioecology of T. cristatus. The modifications might alter their range size and territoriality in the BMKS. Overall, we found that provisioning had negative effects on the ecology of T. cristatus in the BMKS. Therefore, modifying management policies, such as banning feeding and implementing educational programs, may contribute to their proper conservation.

ecology↗

bioRxiv2020

Activity Budget and Postural Behaviours in Orangutans on Bukit Merah Orang Utan Island for Assessing Captive Great Ape Welfare

Assessments of the welfare status of captive and semi-captive animals often compare how their expression of natural behaviours differs from that of free-ranging conspecifics. Bukit Merah Orang Utan Island (BMOUI) is the only orangutan rehabilitation and conservation centre in the Malay Peninsula. We recorded and analyzed the activity budget and postural behaviours of orangutans moving freely in the enclosures on BMOUI to evaluate their welfare status. From December 2015 to December 2016, we observed three individuals: an adult male, an adult female and a subadult male, and collected 252 hours of focal data (84 hr/individual). The orangutans activity budget was dominated by resting (60%), feeding (13%), playing (14%) and moving (9%). The study individuals heavily relied on the artificial foods (79.2%), and they spent majority of their time on the ground (85.1%) with occasional arboreal observations like using the wooden tree platform or a rope. Despite some significant individual differences, behavioural categories followed a similar trend: resting > feeding > moving > playing, except that the subadult male spent significantly more time playing (35%) than the two adults (3-4%). The most predominant posture was sitting (47.0%), followed by pronograde standing (29.4%), lying (10.5%) and clinging (4.5%). Our results suggest that orangutans on BMOUI engage in less feeding but more resting, and show less postural diversity, than free-ranging individuals. We propose that appropriate interventions to shift activity budgets, especially feeding vs. resting, and postural behaviours of captive orangutans towards those found in free-ranging orangutans might be beneficial for their welfare and survival; however, the conclusions we can draw are limited due to the small sample size, and thus until the captive behaviours of a larger number of orang-utans has been described, these results must be considered preliminary and just a case study.

animal behavior and cognition↗

bioRxiv2020

Macroscopic digestive anatomy of ring-tailed lemurs (Lemur catta), including a comparison of frozen and formalin-stored specimens

Digestive tract measurements are often considered species-specific, but little information exists on the degree to which they change during ontogeny within species. Additionally, access to anatomical material from nondomestic species is often limited, with fixed tissues possibly representing the only available source, though the degree at which this material is representative in terms of dimensions and weight is debatable. In the present study, the macroscopic digestive tract anatomy (length of intestinal portions, and tissue weights of stomach and intestines) of n=58 Lemur catta (from neonates to 25 years of age) was quantified, of which 27 had been stored frozen and 31 fixed in formalin. Particular attention was paid to the caecum and the possible presence of an appendix. The intraspecific allometric scaling of body mass (BM)0.46[0.40;0.51] for total intestine length and BM0.48[0.41;0.54] for small intestine length was higher than the expected geometric scaling of BM0.33, similar to literature results on interspecific scaling. This difference in scaling is usually explained by the hypothesis that the diameter of the intestinal tube cannot increase geometrically, to maintain optimal absorption. Therefore, geometric volume gain of increasing body mass is accommodated by more-than-geometric length scaling. Literature describes L. catta as being variable with respect to the presence of an appendix. No appendix was found in specimens of the present study. The proportions of length measurements did not change markedly during ontogeny, indicating that proportions developed in the foetus are already representative for the adult animal. By contrast, width and tissue-mass scaling of the caecum indicated a disproportionate growth of this organ during ontogeny that was not reflected in its length. Compared to overall intraspecific variation, the method of storage (frozen vs. formalin) had no relevant impact on length or weight measurements.

zoology↗

bioRxiv2020

Factors influencing riverine utilization patterns in two sympatric macaques

Many species of terrestrial animals, including primates, live in varied association with the aquatic (e.g., riverine or coastal) environment. However, the benefits that each species receive from the aquatic environment are thought to vary depending on their social and ecological characteristics, and thus, elucidating those benefits to each species is important for understanding the principles of wild animal behaviour. In the present study, to gain a more complete picture of aquatic environment use, including social and ecological factors in primates, factors affecting riverine habitat utilization of two macaque species (Macaca nemestrina and M. fascicularis) were identified and qualitative comparisons were made with sympatric proboscis monkeys (Nasalis larvatus), which have different social and ecological characteristics. Temporal variation in sighting frequency of macaques at the riverbanks was positively related to the fruit availability of a dominant riparian plant species and negatively related to the river water level which affects the extent of predation pressure. Riverine utilization of macaques was greatly influenced by distribution and abundance of food (especially fruit) resources, possibly in association with predation pressure. Additionally, qualitative ecological comparisons with sympatric proboscis monkeys suggest that the drivers of riverine utilization depend on the feeding niches of the species, and different anti-predator strategies resulting from their differing social structures.

ecology↗

bioRxiv2020

Agent-based simulation for reconstructing social structure by observing collective movements with special reference to single-file movement

Understanding social organization is fundamental for the analysis of animal societies. In this study, animal single-file movement data -serialized order movements generated by simple bottom-up rules of collective movements-- are informative and effective observations for the reconstruction of animal social structures using agent-based models. For simulation, artificial 2-dimensional spatial distributions were prepared with the simple assumption of clustered structures of a group. Animals in the group are either independent or dependent agents. Independent agents distribute spatially independently each one another, while dependent agents distribute depending on the distribution of independent agents. Artificial agent spatial distributions aim to represent clustered structures of agent locations -a coupling of "core" or "keystone" subjects and "subordinate" or "follower" subjects. Collective movements were simulated following two simple rules, 1) initiators of the movement are randomly chosen, and 2) the next moving agent is always the nearest neighbor of the last moving agents, generating "single-file movement" data. Finally, social networks were visualized, and clustered structures reconstructed using a recent major social network analysis (SNA) algorithm, the Louvain algorithm, for rapid unfolding of communities in large networks. Simulations revealed possible reconstruction of clustered social structures using relatively minor observations of single-file movement, suggesting possible application of single-file movement observations for SNA use in field investigations of wild animals.

animal behavior and cognition↗

bioRxiv2020

Non-Parametric Analysis of Inter-Individual Relations Using an Attention-Based Neural Network

O_LISocial network analysis, which has been widely adopted in animal studies over the past decade, enables the revelation of global characteristic patterns of animal social systems from pairwise inter-individual relations. Animal social networks are typically drawn based on geometric proximity and/or frequency of social behaviors (e.g., grooming), but the appropriate metric for inter-individual relationship is not clear, especially when prior knowledge on the species/data is limited. C_LIO_LIIn this study, researchers explored a non-parametric analysis of inter-individual relations using a neural network with the attention mechanism, which plays a central role in natural language processing. The high interpretability of the attention mechanism and flexibility of the entire neural network allow for automatic detection of inter-individual relations included in the raw data, without requiring prior knowledge/assumptions about what modes/types of relations are included in the data. For these case studies, three-dimensional location data collected from simulated agents and real Japanese macaques were analyzed. C_LIO_LIThe proposed method successfully recovered the latent relations behind the simulated data and discovered female-oriented relations in the real data, which are in accordance with previous generalizations about the macaque social structure. C_LIO_LIThe proposed method does not exploit any behavioral patterns that are particular to Japanese macaques, and researchers can use it for location data of other animals. The exibility of the neural network would also allow for its application to a wide variety of data with interacting components, such as vocal communication. C_LI

animal behavior and cognition↗