Group-living animals, including penguins, exhibit affiliative behaviors such as grooming (preening) and proximity. Such behaviors in non-primate animals have been less studied than those in primates. Our research focused on 20 identifiable Humboldt penguins in a zoo, analyzing kin relationships and reciprocity in preening and proximity by employing a 5-minute scan sampling method to observe and record individual behavior. Our findings revealed that preening and proximity were more prevalent among mate pairs. However, among non-mate pairs, such behaviors were more commonly observed between siblings and parent-offspring pairs. Notably, the individuals preened on each other simultaneously in all instances. This study highlights the potential influence of kin selection in shaping the affiliative behavior of penguins. Additionally, our findings indicate that penguins gain benefits from mutual preening. This study contributes to our understanding of social behaviors in non-primate species and emphasizes the need for further comparative studies of various animal taxa to elucidate the evolution of sociality.

Abstract 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.

Among the Macaca species, adult male Japanese macaques are the least likely to perform male care (i.e., affiliative interactions between adult males and immatures, including holding, carrying, and grooming); however, they perform male care for infants, albeit infrequently. We examined 17 cases of male care observed for the first time when the immature was younger than 1 year of age. Eleven of the 31 adult males who remained as central males during the 30-year observation period performed male care. Their age and dominance rank did not influence the occurrence of male care. Most cases were first recorded between the last part of the mating season and the first part of the birth season (January–March), whereas male care was rarely observed during the mating season (October–December). In 12 of the 17 cases, male care ceased within 6 months after the first observation, whereas in the remaining cases, it continued for at least 1 year. In 15 of the 17 cases, males tended to perform male care for matrilineally unrelated female infants of low-ranking mothers. In some cases, the male and infant mother showed grooming interactions for 6 months both before and after the start of male care, whereas such grooming interactions were never recorded either before or after the start of male care in other cases. We also examined some hypotheses on male–immature associations and the probable benefits that males and infants might acquire through male care.

How experience affects the flexibility of facial identity recognition in adulthood is not fully understood. Primatologists are an interesting type of participants investigating facial identity recognition ability and flexibility because they can recognize individual primates based on their appearance, including body and facial features, through intense training during adulthood. Consequently, this study investigates the influence of primatological experience on individual recognition ability using eye-tracking techniques and sequential 2-alternative forced-choice matching tasks with images of humans (Homo sapiens) and Japanese macaques (Macaca fuscata). Results indicated that primatologists recognized faces of Japanese macaques more accurately than did control participants, while both primatologists and control participants recognized humans’ faces with high accuracy. Primatologists demonstrated better recognition of monkey images when the whole body was presented than when only the face was presented, whereas control participants did not. Compared to the control participants, primatologists looked at areas other than the monkeys’ faces for a longer time when whole-body images were presented. Furthermore, primatological experience (including study period and a total number of recognizable subjects in their studies) was related to the extent to which individual recognition of monkeys depended on nonface information. Altogether, our findings indicate that primatological experience improves the viewer’s ability to recognize monkeys’ faces. In addition, if available, primatologists with more experience studying monkeys use information from other parts of the body to recognize individual monkeys. (PsycInfo Database Record (c) 2021 APA, all rights reserved)

This study aimed to quantitatively describe triadic grooming bouts in a free-ranging group of Japanese macaques (Macaca fuscata). Two types of triadic grooming bouts occurred less frequently and for a shorter duration than dyadic grooming bouts: straight-line type (SL), where individual A grooms B, who then grooms C; and two-to-one type (TO), where individuals X1 and X2 groom Y. TO-type grooming was recorded more often than SL-type grooming. As in the dyadic grooming bouts, two females who had direct grooming interactions in both SL-type (i.e., between A and B or between B and C) and TO-type groomings (i.e., between X1 and Y and between X2 and Y) and two groomers who did not have direct grooming interactions in TO-type grooming were closely related to each other in more than the half of the pairs recorded. Groomers were more likely to be subordinate to groomees in triadic grooming. Almost all of the observed pairs in SL- and TO-type groomings were also recorded in dyadic grooming bouts. These findings indicate that like dyadic grooming, triadic grooming bouts are largely influenced by blood relatedness through maternal lines and dominance relationships between participants. Based on affiliative relationships maintained through dyadic grooming, triadic grooming could be influenced by such affiliative relationships and then function to strengthen bonds between participants. Possible relationships between triadic grooming and the level of social tolerance among individuals are discussed from the viewpoints of interspecies differences among macaque species and regional differences in Japanese macaques.

© 2019 Blackwell Verlag GmbH Recently, automated observation systems for animals using artificial intelligence have been proposed. In the wild, animals are difficult to detect and track automatically because of lamination and occlusions. Our study proposes a new approach to automatically detect and track wild Japanese macaques (Macaca fuscata) using deep learning and a particle filter algorithm. Macaque likelihood is derived through deep learning and used as an observation model in a particle filter to predict the macaques’ position and size in an image. By using deep learning as an observation model, it is possible to simplify the observation model and improve the accuracy of the classifier. We investigated whether the algorithm could find body regions of macaques in video recordings of free-ranging groups at Katsuyama, Japan to evaluate our model. Experimental results showed that our method with deep learning as an observation model had higher tracking accuracy than a method that uses a support vector machine. More generally, our study will help researchers to develop automatic observation systems for animals in the wild.

Abstract: Some animals conserve body heat through physical contact with conspecifics (i.e., huddling) under cold climate conditions. However, the factors that promote huddle partner selection have not been clarified. We hypothesized that exchanging grooming for huddling is a beneficial strategy used by female Japanese macaques (Macaca fuscata) to withstand cold temperatures. In this study, we undertook focal sampling of 17 female macaques at Katsuyama, Okayama Prefecture, Japan, between April 2012 and March 2013. We used generalized linear mixed models and determined influential factors based on the Akaike information criterion. As a result, we found that female Japanese macaques were likely to participate in grooming interactions before huddling with adult females, but that they rarely did so before huddling with their young (1-year-old or younger) offspring. In particular, adult females tended to huddle with other adult females after unreciprocated grooming bouts. Moreover, they solicited return grooming less frequently when females huddled after grooming interactions than when they did not huddle after grooming interactions. Finally, we evaluated whether grooming improved huddling position. Immediately after grooming, females huddled at advantageous positions more often than they huddled without grooming, and relative benefit by huddling position in the groomer was likely to be larger than the groomee. In contrast, when females huddled after reciprocal grooming, females tended to huddle in positions that were equally beneficial to both females. Overall, our results suggest that female Japanese macaques, particularly those without young offspring, exchange grooming for huddling with other adult females. Significance statement: Huddling is a thermoregulatory behavior performed under cold climate conditions however, the factors promoting huddle partner selection are unclear. In several animal species, including primates, individuals exchange grooming for reciprocal grooming or other social benefits, such as access to infants and agonistic support. This study showed that during winter, female Japanese macaques obtain huddling benefits in exchange for grooming. However, females with young offspring were unlikely to use grooming to huddle with adult females because their offspring act as huddling partners. Thus, the use of grooming by Japanese macaques as a payment is flexible, depending on the needed benefits of the individuals. To our knowledge, this is the first study to suggest that huddling is a potential commodity that females trade in exchange for grooming.

<p>Group-living primates often perform complex social behaviors. Traditionally, observational and experimental studies have provided important insights into the social behaviors of primates; however, these studies have limitations regarding unambiguous causality. The use of artificial stimuli can aid in understanding the mechanisms of animal behavior. A robot, which can perform some behavior sequences automatically or by remote control, serves as a new method to study the response of an animal to the stimulus of the same or other species. One of the advantages of using a robot is that researchers can change the appearance and behavior in line with their purpose. In addition, using a robot can help investigate the influence of more than one individual on another individual's behaviors. Although it is advantageous to use robots in the study of animal behaviors, it entails various challenges. This paper reviews the studies on animal behavior that used robots as stimuli and discusses the contribution of using robots in primate behavior study in the future.</p>

<p>Group-living primates are likely to spend a substantial amount of time grooming and resting with a small number of other group members. Such close and enduring relationships are regarded as affiliative. The properties of affiliative relationships are not fully understood and no consensus exists on how to quantitatively describe them. In this review, I explain the primate behaviors that are related to affiliative relationships and examine the means for using these behaviors to measure the relationship. Traditionally, affiliative relationships are defined by the frequency of proximity and grooming. Individuals with frequent proximity and grooming tend to perform altruistic behaviors for their partners without immediate return from them, groom each other in a reciprocal manner in the long-term, show distress and reconcile after agonistic interactions, and synchronize their behaviors with those of their partners. Thus, in addition to measuring the frequencies of proximity and grooming, these behavioral tendencies might be used as indices of affiliative relationships. Similarly, other questions concerning affiliative relationships remain unexplained. Some studies show that affiliative relationships increase reproductive success, but the mechanisms leading to fitness outcomes remain unclear. Although typically in primates, related individuals tend to form affiliative relationships, such relationships are also formed with unrelated individuals. Affiliative relationships could mitigate the negative effects of competition among individuals in large social groups and ensure that the individuals that form the relationship receive benefits from each other (e.g., agonistic support and collective mobbing). It is also unclear whether the affiliated relationships of nonhuman primates are equivalent to those of humans. Further research is necessary to elucidate similarities or differences in affiliative relationships between human and nonhuman primates.</p>

It is unclear whom animals select to huddle with for thermoregulation. In this study, we investigated whom Japanese macaque (Macaca fuscata) mothers huddled with-their young offspring or other adult group members-when there is need for thermoregulation. We used a focal-animal sampling method, targeting 17 females at Katsuyama, Okayama Prefecture, Japan. A majority of huddling among adult females was recorded during winter season (December, January, and February). Females who had young (0- or 1-year-old) offspring huddled less frequently with other adult females compared to females who did not have young offspring in winter. However, including young offspring, the frequency of huddling with any other individuals did not differ by whether females had young offspring. Moreover, the females who did not have young offspring huddled with other adult females more often in cloudy than in sunny weather during winter season. In contrast, females who had young offspring increased huddling with their young offspring in cloudy than in sunny weather, but did not do so with other adult females. This study indicates that Japanese macaque mothers huddle with their young offspring instead of other adult females when there is need for thermoregulation. (C) 2016 Elsevier B.V. All rights reserved.

<p>Many researchers have investigated why and how animals benefit from each other in a group. Grooming is considered as prosocial behavior in animal societies; the groomer expends time and energy costs, while the groomee receives hygienic and physiological benefits. Based on the reciprocal altruism hypothesis (Trivers, 1971), many researchers have investigated grooming behaviors in primate species. In primates, individuals exchange grooming for grooming or other social benefits (e.g., tolerance for food, agonistic support, or infant handling). Researchers have also established and modified models of grooming reciprocity. In future researches, it would be valuable to investigate the effects of affiliative elationships, soliciting behaviors, self-rewarding, inequity aversion, and partner choice and partner switching on prosocial behaviors.</p>

In animal societies, the effect of grooming interactions on anxiety reduction is unclear. This study examined the effects of giving and receiving grooming on anxiety reduction in free ranging female Japanese macaques (Macaca fuscata) by measuring rates of self-scratching as an index of anxiety. In this study, the authors used a focal-animal sampling method, targeting 17 females at Katsuyama, Okayama prefecture, Japan. They evaluated affiliative relationships, which were defined by standard proximity rates, and found that females' self-scratching rates were lower after grooming affiliated partners than during matched-control periods (occurring on another day, beginning at approximately the same time of day as the corresponding postgrooming period) and not after grooming unaffiliated partners. Moreover, regardless of affiliative relationships, self-scratching rates were lower after receiving grooming than during matched-control periods. These findings did not change after excluding data in which groomer and groomee were in proximity after the grooming interaction. In addition, multivariable analysis showed that affiliative relationships, but not kinship or rank distances, were related to differences in the rates of self-scratching between giving grooming and matched-control periods. In contrast, neither affiliative relationships nor kinship nor rank distances affected differences in self-scratching rates between receiving grooming and matched-control periods. Therefore, individuals' anxiety levels decreased both after giving grooming to affiliated partners and after receiving grooming, regardless of affiliative relationships. This is the first empirical study to support the notion that giving grooming to affiliated partners is self-rewarding in Japanese macaques.

In group-living primates, individuals often exchange grooming with not only kin but also non-kin. We investigated the effect of soliciting behaviors on grooming exchanges in a free-ranging Japanese macaque (Macaca fuscata) group at Katsuyama. In this study, we used a focal animal sampling method, targeting 14 females. Data were collected for 15.75 +/- A 2.67 (mean +/- A SD) hours per focal female. We classified female-female pairs into three pair types: kin pairs, affiliated non-kin pairs, and unaffiliated non-kin pairs. Females received grooming more frequently when they solicited after grooming their partners than when they did not solicit in all pair types. In addition, females received grooming less frequently when they did not groom their unaffiliated non-kin partners before soliciting; prior grooming was not needed to receive grooming from kin or affiliated non-kin partners. The degree of grooming reciprocity did not differ according to the frequency with which females in kin or affiliated non-kin pairs solicited after grooming. On the other hand, grooming reciprocity between unaffiliated non-kin females was more balanced when they solicited frequently after grooming, as compared with when they did not. In conclusion, our study suggests that soliciting behaviors promote grooming exchanges in female Japanese macaques.

野生ニホンザルをスマートフォンで撮影することで、個体の名前や特徴が表示されるシステムの構築を目指している。岡山県真庭市に生息している勝山ニホンザル集団の個体を対象に、画像データを収集して、識別器の作成を進めている。現時点で、51頭の成体メスに関して高い水準で識別ができるようになった。しかし集団に所属するすべての成体メスの識別が可能になったわけではないため、画像データの収集を進めたが、新型コロナウイルスの流行により、十分なデータを収集することができなかった。

人を含む霊長類の多くは集団を形成する。集団内では、他者を個体識別し、それぞれの他個体と社会関係を築いている。本研究課題では、他者の顔を識別する能力が、どの程度生得的で、どの程度後天的なのかを探り、動物の中でも際立つ人の社会性の基盤を解明することを目指す。サルの個体識別をした経験を持つサル研究者と一般成人を対象として、成人期における顔の識別能力の柔軟性を検討した。結果として、成人した後であっても、サルを見る経験を積むことによって、サルの識別能力が向上することが示唆された。この研究成果は、国際学術雑誌であるJournal of Comparative Psychology誌において2021年に公開された。 また、本研究課題では、ニホンザルの個体識別を行うプログラムを深層学習を用いて開発した。深層学習と逐次ベイズ更新を組み合わせることによって、高い精度でニホンザルの識別を行うことが示唆された。この研究成果は、国際学術雑誌であるEthology誌において、2022年3月にonline firstの形で公開された。

インテンシブ・アプローチとして、1）抱擁行動が見られない個体群においてその代替行動の研究を行った。岡山県勝山群を対象として、2019年4月から翌年3月にかけて、合計58日の調査を行った。前年度から引き続きオトナメス間の社会交渉を観察したところ、リップスマッキング（表情）やガーニー（音声）は、0歳齢を持つ個体に接近するときに多く行われており、攻撃交渉後や毛づくろい交渉の開始前に行われることもあった。勝山群において、リップスマッキングやガーニーが個体間の緊張緩和行動として機能している可能性が考えられることが分かった。また、2）抱擁行動が見られるがこれまで知られているものとは異なる組み合わせで起こっていることがわかりつつあった上野動物園の放飼場群35頭について2019年9月から翌年1月にかけて215時間の調査を行った。計202回の抱擁行動を観察したが、その組み合わせはメス間が4%、オスメス間が89%、オス間が7%となった。抱擁行動をした個体は、オトナメス17頭中わずか3頭、ワカモノメス3頭中全3個体、オトナオス8頭のうち3頭、ワカモノオス7頭中6頭であった。野生下では抱擁行動は主にオトナメス同士で行われており、オトナオスが関わった事例は少ないため、繁殖制御のためオトナオスのパイプカット、オトナメス黄体ホルモンのインプラントを皮下接種といったかなり特殊な飼育状況が反映されたものと考えられた。 次にエクステンシブ・アプローチとしては、抱擁行動の見られる個体群である屋久島において、群間の変異を探るべく研究協力者とともに2019年7-9月と2020年3月に調査を行ったところ、群れによって抱擁行動の頻度に大きな違いがあることが分かった。また、抱擁行動を含めた社会行動等を中心とした行動の個体群間変異を抽出するアンケートに用いる映像アーカイブ構築に先立ち、そうした行動の映像の収集を行った。

本研究課題は、ヒトを含む霊長類において、同種や他種の他者をどのように認識しているかを探ることを目的としている。平成29年度は、人間の6か月齢児、12か月齢児、成人を対象とした認知実験に着手し、予定していた半分以上のデータを収集した。現在までのデータを用いた予備分析では、当初の仮説に合致する傾向が得られている。また、今後ロボットを用いた実験研究を行うために、他大学の研究者と繰り返し打ち合わせを行い、ロボットの開発を進めている。さらに、霊長類の親密さをどのように評価すればよいか、霊長類の行動研究においてロボットをどのように利用できるか、といった当該の研究課題に関する問題について情報を収集し、計2編の総説論文を執筆し、国内学術雑誌『霊長類研究』に掲載、あるいは掲載予定である（こちらは4月に受理通知を受けた）。また、申請者が昨年度までに行った研究成果を2編の論文にまとめ、国際学術雑誌に投稿し、うち1編は平成30年5月に受理されている。

We collected image and movie data of Japanese macaques at Katsuyama and Awajishima. Using images of Japanese macaques, we have developed an artificial intelligence system that can detect, track, and identify Japanese macaques in videos. By using the time series information of the target individual in the moving image, it was shown that the identification could be carried out with higher accuracy than the conventional method. By using this program, it is thought that even ordinary people can gain a rich observation experience when observing monkeys in zoos or monkey parks.

The foundation of human social intelligence lies in the ability to recognize others and to cooperate with others．Animals such as dogs and horses that live in cooperation with humans have not only been used as human-service animals, but also domesticated as companion animals that form social bond with humans. In this project, we conducted several lines of studies that investigate roles of various type of social signals exchanged between human and animals as non-verbal communications. As a result of studies indicated that these animals could recognize the emotional and cognitive states of humans through social signals, especially facial expression and gaze directions. These recognition abilities from the social signals were learned not only as the simple operant behavior but also as communicative signals through the interactive learning, in which both animals and humans learned each social signal interactively.

葛藤解決行動は、動物が社会的文脈において発揮する認知能力(社会的知性)を明らかにする上で、非常に興味深い研究対象である。対立する2者間で、目的を調和させ、争いをうまく調整する行動は、ヒトを含む社会的動物において、普遍的に存在し、多くの類似性を持つ。そこで本研究では、ニホンザルを対象として、協力的関係を築くための、葛藤解決メカニズムを明らかにすることを目指す。 ニホンザルは、気温が低くなると2個体以上の個体がお互いの胴体を接触させてハドルを形成して暖を取る(Hanya et al. 2007)。一方の個体がハドル形成を望んでいるときに、もう一方の個体も同じくハドル形成を望んでいるとは限らない。そこで本研究では、昨年度勝山ニホンザル集団(岡山県真庭市)を観察して得られたデータを分析して、ニホンザルが、成体メスに毛づくろいを行うことによって、個体間の葛藤を少なくしてハドル形成という利益を得ているのかどうかを検討した。 成体メス同士でハドルを形成するときには、毛づくろい交渉後にハドルを形成することが多かった。そして、成体メス同士でハドルを形成するときには、毛づくろいを行い、そして相手からお返しの毛づくろいを受けていない時に、ハドルを形成することが多くなっていた。以上の結果から、ニホンザルがけつくろいによって葛藤を解決し、ハドル形成という利益を得ていたことが示された。この研究成果は、ハドル形成に伴う葛藤をどのように解決しているのかを示した初めての研究である。