Search

This study implements a computer-assisted content analysis to identify which social grooming factors reduce social media users' incivility when commenting or posting about the COVID-19 situation in South Korea. In addition, this study conducts semantic network analysis to interpret qualitatively how people express their thoughts. The findings suggest that social network size is a negative predictor of incivility. Moreover, Twitter users who have built larger networks and gained positive responses from others are less likely to use uncivil language. Lastly, linguistic choice among users is different depending on the size of their social network.

When primates groom each other, they tend to concentrate on those parts of the body they cannot efficiently self-groom (i.e., not visually accessible), and prefer to intensify grooming in areas with high hair density, thus suggesting a hygienic function. However, preferences for some body sites over others during social grooming may also result from different degrees of social bonding and relative dominance. To assess the relative importance of physical (hygienic) and social factors, we examined grooming interactions in two groups of wild black capuchin monkeys (Sapajus nigritus) during 15 nonconsecutive months. We evaluated the distribution of social grooming across body sites according to their accessibility by self-grooming and hair density. At the same time, we assessed whether the degree of dyadic social bonding affects the relative body orientation between groomer and groomee and the access to vulnerable body sites (e.g., face, throat, groin) during grooming. As expected, capuchins preferentially groomed inaccessible body sites (e.g., back and head), with a disproportionate effort directed to the tufts of their partners. We found that dyadic social bond strength, together with rank distance, significantly affected the proportion of grooming in ventro-ventral body relative orientation only in dominant-subordinate groomer-groomee dyads. This may indicate that, when two individuals differ in rank but are strongly bonded, the level of uncertainty related to the social context is already resolved and thus grooming per se is no longer perceived by the subordinate as an uncertain/risky situation. We found no effect of social bonding on grooming vulnerable body sites for any type of dyad. Our findings suggest that grooming site preferences in black capuchin monkeys simultaneously reflect hygienic and social functions.

Members of social groups risk infection through contact with those in their social network. Evidence that social organization may protect populations from pathogens in certain circumstances prompts the question as to how social organization affects the spread of ectoparasites. The same grooming behaviors that establish social bonds also play a role in the progression of ectoparasitic outbreaks. In this paper, we model the interactions between social organization and allogrooming efficiency to consider how ectoparasitic threats may have shaped the evolution of social behaviors. To better understand the impacts of social grooming on organizational structure, we consider several dynamic models of social organization using network centrality measures as the basis of neighbor selection. Within this framework, we consider the impact of varying levels of social grooming on both the group structure and the overall ectoparasitic disease burden. {Our results demonstrate that allogrooming, along with on-going dynamic social organization, may be protective with respect to both the timing and the magnitude ectoparasitic epidemics.} We find critical differences in both of these protective effects across different emergent social structures. These results support the idea that ectoparasitic threat should not be considered a single evolutionary factor in the evolution of host social systems, and may have operated in different ways depending on the broader ecology of the host-ectoparasite interaction.

Play is sometimes considered as an indicator of positive animal welfare. However, it is not yet sufficiently understood whether or not social play among adults can be considered as such an indicator because it is rare in adult animals. This study investigates the factors that influence social play in adult captive chimpanzees in order to discuss its function and use as a welfare indicator. The subjects were 37 adult chimpanzees (17 males and 20 females) living in Kumamoto Sanctuary, Kyoto University, Japan. We completed 367 h of behavioural observation of mixed-sex and all-male groups of chimpanzees between June and July 2014, and December 2014 and March 2015, respectively. We collected data on social play, social grooming (mutual and unilateral grooming), aggressive interactions, self-directed behaviours and abnormal behaviours. We checked the relationship between social play and age, sex, timing, social group formation and different social behaviours. The results reveal that social play increased in males of all-male groups compared to those of mixed-sex groups. Furthermore, we analysed behaviours in individuals from all-male groups and found that social play increased before feeding. In addition, although mutual social grooming showed a negative correlation with aggressive interactions, social play did not show such a relationship. Furthermore, social play and mutual social grooming were negatively correlated. These results suggest that social play may be used as a means to reduce social tension and that it does not necessarily indicate that the individuals formed affiliative social relationships such as mutual social grooming indicates. Therefore, although social play is important to enable the coexistence of multiple adult males who do not always get along well, we need to be cautious when interpreting social play from the view of animal welfare.

이 연구에서는 20대 여대생들의 소셜 미디어 이용이 마르고 싶은 욕구와 신체 불만족 같은 부정적 신체 이미지 형성에 어떠한 영향을 미치고 있는가를 페이스북 중심으로 살펴보았다. 우선 페이스북 이용 집단과 비이용 집단의 부정적 신체 이미지에서 유의미한 차이가 발생하는가를 살펴보고, 페이스북 이용 집단을 대상으로 부정적 신체 이미지에 영향을 미치는 요인들이 무엇인지 알아보고자 하였다. 부정적 신체 이미지에 영향을 미치는 요인으로 페이스북 이용 시간, 페이스북 친구 수, 페이스북 활동 유형(포스팅 활동/소셜 그루밍 활동), 외모 상향 비교를 포함하였다. 이 연구를 위해 2017년 9월 11일부터 9월 26일까지 수도권 대학의 여대생들을 대상으로 설문 조사를 실시하였다. 총 350명이 설문에 참여하였으나 불성실한 응답자를 제외하고 329명의 응답자가 분석에 포함되었으며, 이 중 페이스북 이용자는 75.1%인 247명 이였다. 연구 결과, 페이스북 이용자가 비이용자보다 더 높은 마르고 싶은 욕구를 보여 주었으며, 이러한 부정적 신체이미지에 영향을 미치는 요인은 단순한 페이스북 노출 시간이 아니라 관계 유지 활동을 위한 소셜 그루밍 활동임이 드러났다. 또한 페이스북상에서 이루어지는 외모 상향비교는 소셜 그루밍 활동이나 부정적 신체 이미지 형성에 중요한 역할을 하는 것으로 나타났다.

Social media have become an integral part of online news use, affecting how individuals find, consume, and share news. By applying the Theory of Reasoned Action (TRA), this study investigates the effects of motives, attitude, and intention on news-sharing behavior among German social media users (n = 333). Findings show that news-sharing attitude and subjective norms have a positive effect on news-sharing intention, which in turn has a positive effect on actual news-sharing behavior. Taken together, we see that a new media behavior in the early phases of its societal diffusion—like social media news sharing in Germany in 2015—can mainly be explained by a rational choice logic and is rooted in the motives of socializing and information seeking. This finding thus reflects the double nature of social media as a means for both information retrieval and social grooming.

The ring-tailed lemur (Lemur catta) is a group-living strepsirhine primate endemic to Madagascar that has a complex vocal repertoire including affiliative moan and hmm calls. Past research has suggested that both vocalisations may be contact calls, and we assessed their usage in addition to examining the effect of individual differences and social factors on male calling behaviour. We tested three hypotheses: the group cohesion, preferred companion and individual differences hypotheses. From March to July 2010, 565 h of focal animal data were collected on 31 males aged ≥1 year at the Beza Mahafaly Special Reserve, Madagascar. Focal males were observed for 30 min, with vocalisations, allogrooming and agonistic interactions noted using one-zero sampling, and general behaviour, nearest neighbour identity and distance noted using instantaneous point sampling, all at 2.5 min intervals. We found support for the group cohesion hypothesis for both vocalisations, and support for the preferred companion and individual differences hypotheses for the hmm but not the moan vocalisation. Moan and hmm calls maintained the distance between a male and his nearest neighbour, and were made at higher rates during behaviours which may lead to separation from conspecifics, such as travel and vigilance. Males made hmm calls at higher rates when they were low-ranking, and/or when the nearest neighbour of a male or a preferred companion of either sex. Low-ranking males may hmm call to maintain proximity to specific individuals within social groups who will show them increased tolerance, with the hmm signalling peaceful intent. Ring-tailed lemurs are one of the best living models of gregarious primate ancestors, and gaining a better knowledge of the function and range of usage of their contact calls informs our understanding of the evolution of primate cognition.

International audience; Behavioural adjustments to predation risk may impose costs on prey species. While the vigilance–foraging conflict has been extensively investigated, other important fitness-related behaviours exclusive to scanning, such as grooming, have been overlooked. Yet, risk perception is expected to be more accurately assessed in these contexts as food-related parameters should not interfere. We studied individually recognizable impalas, Aepyceros melampus, and questioned the factors that shape maternal decision making in two exclusive components of maternal care with high benefits and costs: scanning for predators and grooming offspring to remove parasites. While studies generally infer prey alertness level, used as a proxy of risk perception, from the observed investment in vigilance, the vigilance–allogrooming context gave us the opportunity to directly assess alertness during the time spent head-up, and then to investigate its sources of variation and its consequences for allogrooming probability. We found a strong decrease in allogrooming probability when maternal alertness increased. Mothers were more alert in open (grassland) than in closed (bushland) habitats at a large scale. Increasing group size led both to lower maternal alertness and higher proportion of suckling time spent allogrooming, but only when surrounded by low vegetation, the reverse being true in high vegetation. Finally, mothers suckling female calves were more alert. Our results underline the determinant role of habitat, shaping both offspring predation risk and the relative conspicuousness or protective value of group mates. We discuss the potential fitness costs associated with the antipredator–antiparasite trade-off faced during maternal care. Our results suggest that prey behaviours other than foraging are essential to identify factors shaping risk perception.

Duets in territorial, pair-living primates may function to maintain intragroup cohesion, promote intergroup avoidance, and assist in territorial and resource defense, as well as advertising and reinforcing pair bonds. Despite the absence of duetting in Javan gibbons (Hylobates moloch), recent playback experiments suggested that Javan gibbon songs also play a role in pair-bond advertisement as well as territorial and mate defense. However, playback experiments only assess motivations of the listener, which may not reflect the motivations of the caller. We conducted an observational study of naturally occurring female songs in two groups of Javan gibbons from July 2009 to March 2010 and from March to November 2011 in Gunung Halimun–Salak National Park, Indonesia. We investigated female singing rates in relation to singing location, daily path length, occurrence of intergroup encounters, feeding rate, allogrooming rate, and distance between pair mates. The two females produced 47 songs during 164 observation days. Females in the area of their home range that overlapped with neighboring groups sang more frequently than expected based on time spent in the area of overlap vs. the home range interior. Groups also had longer daily path lengths on days when females sang than on nonsinging days, and on days when they visited the area of overlap than on nonvisiting days. Our findings indicate that, like the duets of other pair-living territorial primates, female Javan gibbon songs function for territorial defense, but we found no support for other functions such as intergroup avoidance, resource defense, and pair-bond reinforcement.

In group-living animals, allogrooming is a common, heterogeneously distributed affiliative behaviour. Among non-human primates, Barrett et al. (1999) predicted ways in which Biological Markets principles interact with competitive regimes to influence grooming reciprocity and interchange. Most tests of these predictions, done at a group level, have produced inconsistent results. Here we take a novel approach by testing these predictions across individuals within a group. This is based on the premise that in groups facing moderate-to-high within-group-competition, individuals vary in their abilities to access resources based on their competitive abilities, causing them to pursue different grooming exchange strategies. We examine evidence for grooming reciprocity and interchange for tolerance at drinking sources among adult females within a group of rhesus macaques (Macaca mulatta) on Cayo Santiago. We test the above premise by assessing hierarchical steepness, and the relationship between individuals’ David’s scores (DS) and access to drinking sources. Finally, we examine the relationship of DS with grooming reciprocity and interchange to see whether they are consistent with the operation of market forces among individuals. Social network comparisons revealed that giving grooming was strongly predicted by both receiving drinking tolerance (interchange) and receiving grooming (reciprocity), despite strong associations with proximity and maternal kinship. The group showed a moderately steep hierarchy, and negative correlations between individuals’ David’s scores and difficulties in accessing drinking stations. Finally, we found partial support for a market-based explanation. Individuals with relatively low David’s scores were more likely to interchange grooming with drinking tolerance. However, grooming reciprocity wasn’t greater among individuals with higher David’s scores. Our findings suggest that multiple explanatory frameworks — reciprocity, market-based interchange, and/or proximity-mediated interchange/social bond investment — may all shape rhesus grooming exchange patterns. Future directions include examining evidence for additional forms of grooming interchange, and the influence of between-group-competition and stress-indicators on grooming reciprocity.

Many species use touching for reinforcing social structures, and particularly, non-human primates use social grooming for managing their social networks. However, it is still unclear how social touch contributes to the maintenance and reinforcement of human social networks. Human studies in Western cultures suggest that the body locations where touch is allowed are associated with the strength of the emotional bond between the person touched and the toucher. However, it is unknown to what extent this relationship is culturally universal and generalizes to non-Western cultures. Here, we compared relationship-specific, bodily touch allowance maps across one Western ( N = 386, UK) and one East Asian ( N = 255, Japan) country. In both cultures, the strength of the emotional bond was linearly associated with permissible touch area. However, Western participants experienced social touching as more pleasurable than Asian participants. These results indicate a similarity of emotional bonding via social touch between East Asian and Western cultures.

In an individualized animal society, social bonds can foster cooperation and enhance survival and reproduction. Cooperative bonds often exist among kin, but nonkin can also develop high-investment cooperative bonds that share similarities with human friendship. How do such bonds form? One theory suggests that strangers should ‘test the waters’ of a new relationship by making small initial cooperative investments and gradually escalating them with good partners. This ‘raising-the-stakes’ strategy is demonstrated by human strangers in short-term economic games, but it remains unclear whether it applies to helping in a natural long-term social bond. Here we show evidence that unfamiliar vampire bats (Desmodus rotundus) selectively escalate low-cost investments in allogrooming before developing higher-cost food-sharing relationships. We introduced females from geographically distant sites in pairs or groups and observed that bats established new reciprocal grooming relationships, and that increasing grooming rates predicted the occurrence of first food donations, at which point grooming rates no longer increased. New food-sharing relationships emerged reciprocally in 14% of female pairs, typically over 10-15 months, and developed faster when strangers lacked alternative familiar partners. A gradual grooming-to-sharing transition among past strangers suggests that ‘raising the stakes’ might be more evident when tracking multiple cooperative behaviours as new relationships form, rather than measuring a single behavior in an established relationship. ‘Raising the stakes’ could play a similar underappreciated role across a broader spectrum of social decisions with long-term consequences, such as joining a new social group or forming a long-term pair-bond.Significance statementVampire bats form long-term cooperative social bonds that involve reciprocal food sharing. How do two unrelated bats go from being strangers to having a high-investment food-sharing relationship? We introduced unfamiliar bats and found evidence that low-cost grooming paves the way for higher-cost food donations. Food sharing emerged in a reciprocal fashion and it emerged faster when two strangers did not have access to their original groupmates. The bats that formed new food-sharing relationships had a history of escalating reciprocal grooming up until the food sharing began. Our finding that unfamiliar nonkin vampire bats appear to gradually and selectively transition from low-cost to high-cost cooperative behaviors is the first evidence that nonhuman individuals ‘raise the stakes’ when forming new cooperative relationships.

In domestic cattle, the relationship between dominance and allogrooming behaviour has been investigated in several studies. However, the results do not show a consistent pattern. The aim of this study was to investigate this relationship in a stable female beef cattle herd using social network analysis as a novel methodological approach. We tested two adaptive allogrooming hypotheses. The ‘Grooming-for-Commodity’ hypothesis posits that allogrooming is directed from low ranking animals towards higher ranking cows in exchange of tolerance and other favours. The ‘Grooming-for-Stability’ hypothesis predicts that allogrooming is performed by high ranking animals down the hierarchy in order to perpetuate the stability of the social structure. We recorded a herd of 15 Gasconne cows on pasture for 3 weeks (180 h) and recorded 681 agonistic interactions and 288 allogrooming events. To evaluate the relationship between dominance and allogrooming behaviour we calculated correlations between dominance index, individual behavioural effort (OUT-direction), and individual attractiveness (IN-direction). We found that more dominant animals provided much higher amount of allogrooming acts (p

Research examining the impact of social media use on the well-being of digital natives has resulted in a myriad of opposing outcomes indicating both positive and negative effects. Focusing on positive effects only, this study examines whether there is a boundary between online and offline realms in cohorts of student digital natives and what differences exist between German and US populations. Using data collected in 2013 and 2014 we find that social grooming activities in social networking sites (SNS) significantly increase positive emotional outcomes and indirectly increase subjective well-being. We also conclude that there is a significant impact of online social grooming activities on offline social activities. But this impact is significantly moderated by cultural aspects: only within the subsample of US students is this effect of spreading social capital from online to face-to-face interaction significant. This striking result can be attributed to the stronger separation of communication act...

Research on leadership is a critical step for understanding collective decision making. However, only 4 of the 22 extant macaque species have been examined for the impact of social rank and affiliation on the initiation of collective movement. It is far from clear whether such impact exists and, if so, how it works among other macaques. To answer these questions, we investigated free-ranging, Tibetan macaques' (Macaca thibetana) group departures from a provisioning area and tested two alternative hypotheses: personal versus distributed leadership. Personal leadership predicts that a single, highest ranking individual initiates the most group movements, whereas distributed leadership predicts that different members lead the group on different occasions and affiliative individuals have more initiations. We recorded how often and how successfully adults initiated group movements from a provisioning area into the forest, and related these variables to the duration of interindividual proximity and grooming time in the forest. All adults initiated group movements, but did so variably. Social rank was related neither to the number of successful initiations nor to the success ratio of initiations. By contrast, eigenvector centrality based on proximity relations was positively correlated with the number and ratio of successful initiations. Moreover, successful initiations were positively correlated with social grooming. Overall, Tibetan macaques showed a pattern of distributed leadership. Our study demonstrated the relationship between social affiliation and individual leadership in a macaque society. Am. J. Primatol. 78:816-824, 2016. © 2016 Wiley Periodicals, Inc.

Strong social relationships confer health and fitness benefits in a number of species, motivating the need to understand the processes through which they arise. In female cercopithecine primates, both kinship and dominance rank are thought to influence rates of affiliative behaviour and social partner preference. Teasing apart the relative importance of these factors has been challenging, however, as female kin often occupy similar positions in the dominance hierarchy. Here, we isolated the specific effects of rank on social relationships in female rhesus macaques by analysing grooming patterns in 18 social groups that did not contain close relatives, and in which dominance ranks were experimentally randomized. We found that grooming was asymmetrically directed towards higher-ranking females and that grooming bouts temporarily decreased the likelihood of aggression between grooming partners, supporting the idea that grooming is associated with social tolerance. Even in the absence of kin, females formed the strongest grooming relationships with females adjacent to them in rank, a pattern that was strongest for the highest-ranking females. Using simulations, we show that three rules for allocating grooming based on dominance rank recapitulated most of the relationships we observed. Finally, we evaluated whether a female's tendency to engage in grooming behaviour was stable across time and social setting. We found that one measure, the rate of grooming females provided to others (but not the rate of grooming females received), exhibited modest stability after accounting for the primary effect of dominance rank. Together, our findings indicate that dominance rank has strong effects on social relationships in the absence of kin, suggesting the importance of considering social status and social connectedness jointly when investigating their health and fitness consequences.

Summary Social bonds, maintained by mutual investments of time and energy, have greatly influenced the evolution of social cognition and cooperation in many species [e.g., 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. However, there are two pitfalls regarding “social bonds” as an explanation for social structure and cooperation [ 1 , 9 , 10 , 11 ]. First, studies often incorrectly assume that frequent association implies partner fidelity based on mutual social preference, but even seemingly complex nonrandom interaction networks can emerge solely from habitat or spatial structure [ 12 , 13 , 14 , 15 , 16 ]. Second, the false appearance of partner fidelity can result from stable options in the “partner market” [ 1 , 9 , 10 , 11 , 17 ]. For instance, individuals might preferentially groom the same partner, even if the decision depends entirely on the immediate costs and benefits rather than relationship history. Given these issues, a key challenge has been testing the extent to which social structure is driven by the intrinsic relationship history versus the extrinsic physical and social environment. If stable bonds exist, they should persist even if the individuals are moved to a dramatically different physical and social environment. We tested this prediction by tracking social relationships among common vampire bats (Desmodus rotundus) moved from the lab to the wild. We show that allogrooming and food sharing among female vampire bats induced in captivity over 22 months predicted their assortativity and association rates when we subsequently tracked them in the wild with custom-made high-resolution proximity sensors. The persistence of many relationships across different physical and social environments suggests that social structure is caused by both extrinsic constraints and intrinsic partner fidelity.

The aim of this study is to examine the relationship between Facebook use, appearance comparison with peers, and body image concerns among young Korean women. Focusing on two major types of social media activities (i.e., profile maintenance, social grooming), this study investigated whether these specific types of user activities would be significantly related to greater appearance comparison with peers, and in turn, would be linked to increased levels of body image concerns. An online survey ( N = 305) was conducted among young Korean women (aged 18–29) in Korea. Results indicated that the frequency with which Korean female participants engaged in profile maintenance and social grooming activities on Facebook was positively associated with appearance comparison with peers, and the mediation analysis revealed that appearance comparison mediated the relationship between Facebook use variables and body image concerns, such as lower weight satisfaction and greater drive for thinness. Theoretical and practical implications for these findings are further discussed.

In many social species, there exist a few highly connected individuals living among a larger majority of poorly connected individuals. Previous studies have shown that, although this social network structure may facilitate some aspects of group-living (e.g., collective decision-making), these highly connected individuals can act as super-spreaders of circulating infectious pathogens. We build on this literature to instead consider the impact of this type of network structure on the circulation of ectoparasitic infections in a population. We consider two ODE models that each approximate a simplified network model; one with uniform social contacts, and one with a few highly connected individuals. We find that, rather than increasing risk, the inclusion of highly connected individuals increases the probability that a population will be able to eradicate ectoparasitic infection through social grooming.

Humans use various social bonding methods known as social grooming, e.g. face to face communication, greetings, phone, and social networking sites (SNS). SNS have drastically decreased time and distance constraints of social grooming. In this paper, I show that two types of social grooming (elaborate social grooming and lightweight social grooming) were discovered in a model constructed by thirteen communication data-sets including face to face, SNS, and Chacma baboons. The separation of social grooming methods is caused by a difference in the trade-off between the number and strength of social relationships. The trade-off of elaborate social grooming is weaker than the trade-off of lightweight social grooming. On the other hand, the time and effort of elaborate methods are higher than lightweight methods. Additionally, my model connects social grooming behaviour and social relationship forms with these trade-offs. By analyzing the model, I show that individuals tend to use elaborate social grooming to reinforce a few close relationships (e.g. face to face and Chacma baboons). In contrast, people tend to use lightweight social grooming to maintain many weak relationships (e.g. SNS). Humans with lightweight methods who live in significantly complex societies use various social grooming to effectively construct social relationships., Accepted by Royal Society Open Science

International audience; Among nonhuman primates, the evolutionary underpinnings of variation in social structure remain debated, with both ancestral relationships and adaptation to current conditions hypothesized to play determining roles. Here we assess whether interspecific variation in higher‐order aspects of female macaque (genus: Macaca ) dominance and grooming social structure show phylogenetic signals, that is, greater similarity among more closely‐related species. We use a social network approach to describe higher‐order characteristics of social structure, based on both direct interactions and secondary pathways that connect group members. We also ask whether network traits covary with each other, with species‐typical social style grades, and/or with sociodemographic characteristics, specifically group size, sex‐ratio, and current living condition (captive vs. free‐living). We assembled 34–38 datasets of female‐female dyadic aggression and allogrooming among captive and free‐living macaques representing 10 species. We calculated dominance (transitivity, certainty), and grooming (centrality coefficient, Newman's modularity, clustering coefficient) network traits as aspects of social structure. Computations of K statistics and randomization tests on multiple phylogenies revealed moderate‐strong phylogenetic signals in dominance traits, but moderate‐weak signals in grooming traits. GLMMs showed that grooming traits did not covary with dominance traits and/or social style grade. Rather, modularity and clustering coefficient, but not centrality coefficient, were strongly predicted by group size and current living condition. Specifically, larger groups showed more modular networks with sparsely‐connected clusters than smaller groups. Further, this effect was independent of variation in living condition, and/or sampling effort. In summary, our results reveal that female dominance networks were more phylogenetically conserved across macaque species than grooming networks, which were more labile to sociodemographic factors. Such findings narrow down the processes that influence interspecific variation in two core aspects of macaque social structure. Future directions should include using phylogeographic approaches, and addressing challenges in examining the effects of socioecological factors on primate social structure.

Reciprocity can generate stable levels of cooperation among unrelated social partners. If individuals interact repeatedly, costs of altruistic acts can be compensated through an exchange of donor and receiver roles. Frequent interactions are conducive to attaining evolutionarily stable reciprocal exchange. High interaction frequencies are typical for group members maintaining close relationships among one another, which may thereby facilitate reciprocity. Norway rats (Rattus norvegicus) are highly social animals that were experimentally shown to reciprocally exchange food donations and allogrooming. Here, we tested experimentally the relationship between reciprocal cooperation and other social behaviours exchanged within dyads of wild-type Norway rats. In particular, we asked whether and how interactions differing in quality (characterised by affiliative and aggressive behaviours) influence reciprocal exchanges of different social services. Our experiment involved three steps: Focal individuals experienced social partners that were either providing them with food or not, via a learnt stick-pulling task. Thereafter, they could either interact physically with these partners, or not. Subsequently, we induced allogrooming among them by applying saltwater to an inaccessible part of the body, and tested for the reciprocation of allogrooming. When individuals were allowed to interact freely, previously cooperative food providers exhibited more aggression towards focal individuals than previously uncooperative partners, which might reflect an attempt to coercively demand a return of food provisioning from focal rats. Higher frequencies of affiliative behaviours and lower frequencies of aggressive behaviours experienced during the unrestricted interaction phase tended to increase the focal rats’ propensity to engage in grooming the partner in the subsequent induced allogrooming phase. This suggests that affiliative and aggressive behaviours affect the allogrooming propensity of rats. In particular, higher frequencies of received aggression decreased the propensity to reciprocate previously received cooperation. We provide experimental evidence that rats are more likely to groom partners that pulled a stick to deliver food to them. Reciprocal exchange of allogrooming depends apparently on experienced cooperation, but also on the quality of the social relationship. Close social relationships among individuals may enhance reciprocal exchange of services and thereby ensure long-term cooperation. Thus, we tested whether in unrelated and previously unfamiliar Norway rats, the quality of social interactions, that is, the amount of exchanged affiliative and aggressive behaviours, affects reciprocal cooperation, and whether received cooperation in turn predicts subsequent social behaviour. Our results show that focal individuals are generally more helpful to previously helpful partners, but that the quality of social interactions may modify their decision to cooperate. Received aggressive and affiliative behaviours affected the subsequent reciprocal exchange of hygienic behaviour. Moreover, received food provisioning affected the exchange of cooperative, affiliative and aggressive behaviours also outside of a food-provisioning context. These data reveal a close relationship between the exchange of social behaviours between individuals and their propensity to cooperate with one another.

GrooFiWorld is an individual-based, computational model of social interactions that can be used to examine factors underlying reciprocation and interchange of social behavior in primate societies. Individuals within GrooFiWorld are programed to maintain spatial proximity and thereby form a group. When an individual encounters another individual in its proximity, the individual attacks the other if the risk of losing is low. Otherwise, the individual considers grooming the other. Patterns of social behavior that emerge in the model resemble empirical data from primates. Triadic aggression emerges when an individual attacks one of the former combatants by chance immediately after an aggressive interaction, and reciprocation and interchange of grooming and support emerge even though individuals have no intention to help others or pay back services. The model generates predictions for patterns of contra-intervention that are counterintuitive within a framework of interchange of social services, such as that individuals receive more contra-intervention from those whom they groom more frequently. Here we tested these predictions in data collected on social interactions in a group of bonnet macaques (Macaca radiata). We confirmed the predictions of the model in the sense that contra-intervention was strongly correlated with dyadic aggression which suggests that contra-intervention is a subset of dyadic aggression. Adult females directed more contra-intervention to those individuals from whom they received more grooming. Further, contra-intervention was directed down the dominance hierarchy such that adult females received more contra-intervention from higher ranking females. Because these findings are consistent with the predictions from the GrooFiWorld model, they suggest that the distribution of interventions in fights is regulated by factors such as dominance rank and spatial structure rather than a motivation to help others and interchange social services.

Group is an essential resource for gregarious animals. Dairy cows are however frequently (re-)grouped according to productivity and reproductive state leading to an unstable social environment for the animals. The present study aimed at investigating whether cows maintain social relationships in a dynamic group. Therefore we analysed whether more familiar cows spend more time in close proximity, and interact more often in an affiliative way. Social interactions and direct neighbours during feeding and resting of 12 Holstein cows (1st to 3rd lactation) in a dynamic dairy cow group of 50 animals were assessed continuously over four days using focal animal sampling. A principal component analysis over the twelve assessed social behaviour variables per pair revealed four main components: social relationships may be characterised by time spent as direct neighbours when feeding and interacting affiliative as well as agonistically (excluding displacements), by displacement success, allogrooming interactions, and time spent as direct neighbours when resting. Long-term (shared youth experience, shared adult experience) and short-term (shared dry-period, synchronised group entry) familiarity was associated with higher scores for interacting and being direct neighbours when feeding (p

Flexibly adapting social behavior to social and environmental challenges helps to alleviate glucocorticoid (GC) levels, which may have positive fitness implications for an individual. For primates, the predominant social behavior is grooming. Giving grooming to others is particularly efficient in terms of GC mitigation. However, grooming is confined by certain limitations such as time constraints or restricted access to other group members. For instance, dominance hierarchies may impact grooming partner availability in primate societies. Consequently specific grooming patterns emerge. In despotic species focusing grooming activity on preferred social partners significantly ameliorates GC levels in females of all ranks. In this study we investigated grooming patterns and GC management in Barbary macaques, a comparably relaxed species. We monitored changes in grooming behavior and cortisol (C) for females of different ranks. Our results show that the C-amelioration associated with different grooming patterns had a gradual connection with dominance hierarchy: while higher-ranking individuals showed lowest urinary C measures when they focused their grooming on selected partners within their social network, lower-ranking individuals expressed lowest C levels when dispersing their grooming activity evenly across their social partners. We argue that the relatively relaxed social style of Barbary macaque societies allows individuals to flexibly adapt grooming patterns, which is associated with rank-specific GC management. Am. J. Primatol. 77:688–700, 2015. © 2015 Wiley Periodicals, Inc.

The exchange of services such as allo-grooming, allo-preening, food tolerance and agonistic support has been observed in a range of species. Two proximate mechanisms have been proposed to explain the exchanges of services in animals. First, an animal can give a service to a partner depending on how the partner behaved towards it in the recent past. This mechanism is usually tested by examining the within-dyad temporal relation between events given and received over short time periods. Second, the partner choice mechanism assumes that animals give favours towards specific partners but not others, by comparing how each partner behaved towards them over longer time frames. As such, the partner choice mechanism does not make specific predictions on a temporal contingency between services received and given over short time frames. While there is evidence for a long-term positive correlation between services exchanged in animals, results for short-term contingencies between services given and received are mixed. Our study investigated the exchange of grooming for food tolerance in a partially provisioned group of Barbary macaques, by analysing the short-term contingency between these events. Tolerance over food was compared immediately after grooming and in control condition, using food of different shareability. We found no evidence that grooming increases food tolerance or decrease aggression around food in the short term. Food tolerance was affected by the shareability of the food and the sex of the partners. The exchanges of grooming and food tolerance in non-human primates may be little affected by recent single events. We suggest that long-term exchanges between services given and received and social partner choice may play a more important role in explaining social interactions than short-term contingent events.

While natural observations show apes use grooming and play as social currency, no experimental manipulations have been carried out to measure the effects of these behaviours on relationship formation in apes. While previous experiments have demonstrated apes quickly learn the identity of individuals who will provide food in a variety of cooperative and non-cooperative situations, no experiment has ever examined how grooming and play might shape the preferences of apes for different individuals. We gave a group bonobos () and chimpanzees () a choice between an unfamiliar human who had recently groomed or played with them and one who had not. Both species showed a preference for the unfamiliar human that had interacted with them over the one who did not. The effect was largely driven by the males of both species while interacting with females showed little effect on their preferences for unfamiliar humans. Subjects showed this preference even though they only had social interactions with one of the unfamiliar humans for a few minutes before each trial and their choices were not rewarded with food differentially. Our results support the long held idea that grooming and play act as a form of social currency in great apes (and likely many other species) that can rapidly shape social relationships, particularly between unfamiliar individuals.

Group living promotes opportunities for both cooperation and competition. Selection on the ability to cope with such opposing social opportunities has been proposed as a driving force in the evolution of large brains in primates and other social species. However, we still know little about the degree of complexity involved in such social strategies. Here, we report advanced social strategies in wild vervet monkeys. Building on recent experimental evidence that subordinate females trade grooming for tolerance from higher-ranking individuals during foraging activities, we show that the audience composition strongly affects this trade. First, tolerance was lower if the audience contained individuals that outranked the subordinate partner, independently of audience size and kinship relationships. Second, we found a significant interaction between previous grooming and relative rank of bystanders: dominant subjects valued recent grooming by subordinates while intermediate ranked subjects valued the option to aggress subordinate partners in the presence of a dominant audience. Aggressors were also more likely to emit coalition recruitment calls if the audience contained individuals that outranked the subordinate partner. In conclusion, vervet monkeys include both recent grooming and knowledge about third-party relationships to make complex decisions when trading grooming for tolerance, leading to a finely balanced trade-off between reciprocation and opportunities to reinforce rank relationships.

Reciprocity is one of the mechanisms that have been proposed to explain the exchange of social behaviors, such as grooming, in animals. Reciprocity assumes that individuals act as the donor and recipient of grooming and switch roles over time to balance the benefits and costs of this behavior. Three main patterns of reciprocity may follow a grooming given: (1) direct reciprocity, where the former recipient returns the grooming to the former donor; (2) indirect reciprocity, where another individual returns the grooming to the former donor; and (3) generalized reciprocity, where the former recipient returns the grooming to another individual. While there is evidence that direct reciprocity plays an important role in various species of animals, the role of indirect and generalized reciprocity is less clear and has been rarely analyzed. We tested the role of direct, indirect, and generalized reciprocity in explaining grooming exchanges of wild Barbary macaques, by analyzing the temporal contingency between giving and receiving grooming. We collected the occurrence and latency of the three types of grooming reciprocation during one-hour long focal sessions run simultaneously on two partners who just stopped grooming (post-grooming session) or who were in proximity (i.e. within 1.5 meters) without grooming each other (control session). We ran the analyses on 284 post-grooming and 63 control sessions. The results revealed a temporal contingency of grooming interactions exchanged according to direct reciprocity but not according to indirect or generalized reciprocity. Our results indicate that grooming distribution in Barbary macaques is partner-specific. We discuss the possible role of cognition and emotions in explaining direct reciprocity in animals.

Funding was provided by SNF-grant 31003A_156152 to Michael Taborsky. If individuals help more those who have previously helped them, stable cooperation may ensue through alternation of roles between donors and recipients. Allogrooming, which is costly to donors and beneficial to recipients, is often exchanged between social partners. Arguably, allogrooming and allopreening are the most frequently exchanged social services and have been used as a standard model of reciprocal cooperation. However, evidence for the application of reciprocity rules among social partners allogrooming each other hitherto is merely correlational. Here, we tested whether female Norway rats (Rattus norvegicus) apply the decision rule characterising direct reciprocity: help someone who has helped you before, by experimentally manipulating both the need for allogrooming and the behavioural response. Furthermore, we checked whether trading of grooming services is influenced by the rank of the social partner. We show that rats groom social partners reciprocally and prefer to do so up the hierarchy, i.e. they groom dominant partners more often than subordinates, while reciprocating with both. This provides experimental evidence that animals render a costly social service by applying reciprocity decision rules when showing a natural hygienic behaviour. The fact that allogrooming is more readily shown up the hierarchy may suggest an appeasing function. Publisher PDF

In this study, we investigated the reciprocal exchanges of grooming, tolerance and reduced aggression in common marmosets (Callithrix jacchus), a cooperatively breeding primate whose groups are typically characterized by uniformly high genetic relatedness and high interdependency between group members. Both partner control and partner choice processes played a role in the reciprocal exchanges of grooming. In contrast, we did not find any evidence of reciprocity between grooming and tolerance over a preferred food source or between grooming and reduced aggression. Thus, reciprocity seems to play a variable role in the exchange of cooperative behaviors in marmosets.

Kin-biased cooperative and affiliative behavior is widespread in social mammals and is expected to increase fitness. However, despite evolutionary benefits of cooperating with relatives, demographic circumstances may influence the strength of kin bias. We studied the relationship between maternal kinship and affiliative behavior among 78 wild adult female blue monkeys (Cercopithecus mitis) from 8 groups monitored for 1–5 years. We compared behavior and kinship matrices, controlling for rank differences. Using multivariate models, we examined effects of demographic variables on the extent to which females groomed disproportionately with close adult female kin. Female blue monkeys, like other cercopithecine primates, generally preferred closer maternal kin for grooming and spatial association, although there was also substantial variation. Kin bias was weakest for association (at 7 m) while feeding, intermediate for closer (1 m) association while resting, and most intense for grooming. Grooming kin bias was stronger when a female had more very close relatives (either her mother or daughters), when her group contained more adult females, when she groomed with a lower percentage of group-mates, and when she had fewer total kin. Dominance rank did not predict variation in kin bias. Females generally groomed with all kin, but in larger groups they increased the number of unrelated grooming partners and total grooming time. The increased kin bias intensity in larger groups resulted from the addition of unrelated partners with whom grooming occurred less often than with kin, rather than from time constraints that drove females to select kin more strongly. In natural-sized groups, it may be common that females groom with all their adult female kin, which are present in limited numbers. The addition of grooming partners in larger groups may benefit female blue monkeys who rely on collective action in territorial defense; group-wide cooperation may thus influence grooming decisions in this species. Am. J. Primatol. 77:109–123, 2015. © 2014 Wiley Periodicals, Inc.

Along with social grooming and food sharing, social play is considered to be an affiliative interaction among wild chimpanzees. However, infant, juvenile, and adolescent animals engage in social play more frequently than adult animals, while other affiliative interactions occur more commonly between adults. We studied the social play of well-habituated and individually identified wild chimpanzees of the M group in Mahale Mountains National Park, Tanzania over two research periods in 2010 and 2011 (21 and 17 observation days, respectively). In both periods, most members of the M group, including adolescents and adults, took part in social play at least once. The degree centralities of the play network in infants, juveniles, and adolescents were significantly higher than those seen in adults. There was a significant and positive correlation between the total number of participations in social play and the degree centrality of play networks. Partial play networks and partial association networks consisting of individuals in same-age categories were significantly and positively correlated in infants and juveniles, although they were not correlated in adolescents or adults. These results suggest that infants, juveniles and adolescents who played frequently were more central in the group, whilst the adults who played infrequently were more peripheral. In addition, the overall structure of the social play network was stable over time. The frequency of participation in social play positively contributed to the development of affiliative social relationships within the chimpanzee group during the infant or juvenile period, but did not have the same effect during the adolescent and adult period. The social play network may allow individuals to develop the social techniques necessary to acquire a central position in a society and enable them to develop affiliative relationships during the infant or juvenile period.

This study explores the relationship between perceived bridging social capital and specific Facebook-enabled communication behaviors using survey data from a sample of U.S. adults N=614. We explore the role of a specific set of Facebook behaviors that support relationship maintenance and assess the extent to which demographic variables, time on site, total and "actual" Facebook Friends, and this new measure Facebook Relationship Maintenance Behaviors predict bridging social capital. Drawing upon scholarship on social capital and relationship maintenance, we discuss the role of social grooming and attention-signaling activities in shaping perceived access to resources in one's network as measured by bridging social capital.

Unidirectional grooming is a low-cost behaviour for which the groomer is repaid via kin selection or reciprocity. Return benefits can come in the form of increased probability of being groomed or social benefits such as coalitionary support. By contrast, the reasons for mutual grooming, which occurs when two individuals simultaneously groom each other, are not understood. In this study, we test three hypotheses regarding the function of mutual grooming among wild male chimpanzees, using 16 years of data. The social bonding hypothesis posits that mutual grooming promotes a return benefit by serving to strengthen and maintain social bonds, whereas the immediate investment hypothesis states that it functions as a signal to indicate willingness to invest in (continue) the grooming bout. The switching hypothesis states that mutual grooming results from overlap created when the direction of the grooming interaction is switched. The social bonding hypothesis was not supported: measures of association were not correlated with the probability of mutual grooming. We also found no support for the switching hypothesis, as mutual grooming was equally likely to occur without a switch in the direction of grooming as when a switch occurred. The immediate investment hypothesis was supported by our finding that bouts with mutual grooming (1) were longer, (2) contained a more equitable distribution of unidirectional grooming and (3) had more unidirectional grooming switches than bouts without mutual grooming. We conclude that male chimpanzees use mutual grooming to obtain short-term benefits in the form of prolonging a grooming bout, and suggest that mutual grooming thus represents a form of overlapping parcelling.

Mutual grooming plays a central role in the establishment and maintenance of social relationships in primates. Allogrooming has two main functions: hygiene and bonding with partners. The duration of grooming bouts is commonly used in studies of the functional aspects of grooming, but few reflect on the proximate mechanisms that determine grooming bout lengths. As it is highly unlikely that groomer and groomee prefer exactly the same bout length, we are likely to observe the result of some form of negotiation. We currently lack information about the signals that primates employ to inform others about their intentions and desires concerning grooming interactions. From October 2006 until April 2007 we studied three behaviors shown in grooming interactions that could potentially have a signaling function in the negotiation process over the initiation and length of grooming bouts among adult females of two vervet groups freely ranging in the Loskop Dam Nature Reserve, South Africa: approaching another individual as far as that resulted in a grooming session, changing of the body position by the groomed individual, and lip smacking. We found that “approach” did not reliably predict which individual would receive grooming first, although approaching individuals groomed significantly more than those approached. Thus, in the context of grooming interactions, moving toward a group member may signal the willingness to invest. Body part presentations appeared to be the main signal used to demand a prolongation of the grooming by the partner. Finally, lip smacking was used under potentially stressful circumstances, notably shortly before using the mouth to groom the partner or an attempt to touch a mother’s infant. Our exploratory study hopefully inspires colleagues to start looking at the role of communication during cooperative interactions for a better appreciation of how animals manage cooperation and negotiate exchange rates.

Explaining cooperative behaviour is a fundamental issue for evolutionary biology. The challenge for any cooperative strategy is to minimize the risks of nonreciprocation (cheating) in interactions with immediate costs and delayed benefits. One of a variety of proposed strategies, the raise-the-stakes (RTS) strategy, posits that individuals establish cooperation by increasing investment across interactions from an initial interaction. This model has received little quantitative support, however, probably because individuals of many social species engage in repeated interactions from a young age. In some situations, however, such as following conflicts, after prolonged absences or during social instability, established relationships may become unreliable predictors of future behaviour, creating an environment for RTS. We investigated grooming interactions among wild male chimpanzees, Pan troglodytes , testing RTS in these specific contexts. We found evidence to support the view that male chimpanzees employed RTS during social instability, but not under the other conditions. However, we also found that the duration of episodes (discrete parcels) of grooming was negatively related to aggression risk and in consequence suggest that the patterning of grooming interactions indicative of RTS was less to do with preventing cheating, and more to do with avoiding the elevated risks of intramale aggression during the period of social instability. We interpret the apparent support for RTS in our data as a by-product of the way chimpanzees cope with fluctuating (here, elevated then diminishing) risks of aggression. We suggest that social instability raises the stakes for grooming by creating a more hazardous marketplace in which to trade.

In several primate species, adult males are reported to compete for access to reproductive partners as well as forming affiliative and cohesive social bonds based on the exchange of goods or services. We hypothesized that among a broad set of fitness-maximizing strategies, grooming can be used by individual adult males to enhance social relationships through reciprocity and/or through the interchange of grooming for a different but equivalent good or service. We used focal animal sampling and continuously recorded dyadic grooming and agonistic interactions to test a series of predictions regarding male social interactions in a free-ranging group of Tibetan macaques (Macaca thibetana) at Huangshan, China. During the non-mating season or between males of similar rank throughout the year, grooming effort given was matched by grooming effort received. However, lower ranking males groomed higher ranking males at a greater rate and/or for a longer duration during both the mating and non-mating periods. We found that higher ranking males directed less aggression towards males with whom they formed a frequent grooming partnership, indicating that grooming received was interchanged for increased social tolerance. These data suggest that individual male Tibetan macaques employ alternative social strategies associated with grooming reciprocity or interchange depending on dominance rank and rates of aggression, and highlight the importance of both biological markets and grooming reciprocity as behavioral mechanisms used by resident adult males to form and maintain affiliative social bonds.

Seyfarth’s model of social grooming proposes that by grooming females higher ranking than themselves, females can gain access to important rank-related benefits, such as agonistic support. This, in turn, produces a distinctive pattern of grooming in which females direct their grooming up the female dominance hierarchy and compete for access to the highest ranking individuals. We aimed to test to what extent the grooming behavior of female Assamese macaques (Macaca assamensis) fits the assumptions and predictions of Seyfarth’s model. During two 1-yr sampling periods (October 2007–September 2008, May 2010–April 2011) we collected >2100 focal hours of data from a single wild group in their natural habitat at Phu Khieo Wildlife Sanctuary, Thailand. Subjects included all adult female group members (N = 12 in 2007/8; N = 15 in 2010/11). We collected detailed data on grooming interactions, approaches, and departures as well as all aggressive and submissive behaviors between all subjects. We found no evidence that grooming was exchanged for rank-related benefits. In line with this we found no evidence that the grooming of female Assamese macaques fits the pattern predicted by Seyfarth’s model. These results are surprising given that such deviations from Seyfarth’s model are relatively rare among macaques. We propose that our findings are best explained as a lack of a need for rank-related benefits by females in this group.

Chimpanzees (Pan troglodytes) groom in gatherings in which many individuals may be connected via multiple chains of grooming and they often exchange partners with each other. They sometimes groom another while receiving grooming; that is, one animal can play two roles (i.e., groomer and groomee) simultaneously. Although this feature of chimpanzees is notable from the viewpoint of the evolution of human sociality, information on our other closest living relative, the bonobo (Pan paniscus), is still lacking. In this study, I describe grooming interactions of bonobos at Wamba in the Luo Scientific Reserve, Democratic Republic of the Congo (DR Congo), with a particular focus on the formation of grooming gatherings. Like chimpanzees, the bonobos also performed mutual grooming (two individuals grooming each other simultaneously) and polyadic grooming (three or more individuals). However, unlike chimpanzees, these sessions lasted for only a short time. Bonobos rarely groomed another while receiving grooming. Because social grooming occurred not only in trees but also in open spaces, including treefall gaps, the conditions did not necessarily limit the opportunity to make multiple chains of grooming. However, bonobos also engaged in social grooming in different ways from chimpanzees; That is, many individuals were involved simultaneously at a site, in which they separated for dyadic grooming. Some cases clearly showed that bonobos preferred a third party not to join while grooming in a dyad, suggesting that bonobos have a preference for grooming in dyads and that immature individuals formed the preference that was shared among adults while growing up. Most members of the study group ranged together during the majority of the study period. Although bonobos show a fission-fusion grouping pattern, when group members frequently encounter one another on a daily basis, they may not be motivated to form multiple grooming chains at this site, as do chimpanzees.

A society is a complex system composed of individuals that can be characterized by their own attributes that influence their behaviors. In this study, a specific analytical protocol based on social network analysis was adopted to investigate the influence of four attributes (gender, age, matriline, and hierarchical rank) on affiliative (allogrooming) and agonistic networks in a non-human primate species, Macaca sylvanus, at the park La Forêt des Singes in France. The results show significant differences with respect to the position (i.e., centric, peripheral) and role (i.e., implication in the network cohesiveness) of an individual within a social network and hence interactional patterns. Females are more central, more active, and have a denser ego network in the affiliative social network tan males; thus, they contribute in a greater way to the cohesive structure of the network. High-ranking individuals are likely to receive fewer agonistic behaviors than low-ranking individuals, and high-ranking females receive more allogrooming. I also observe homophily for affiliative interactions regarding all attributes and homophily for agonistic interactions regarding gender and age. Revealing the positions, the roles, and the interactional behavioral patterns of individuals can help understand the mechanisms that shape the overall structure of a social network.

Our study (1) describes the behavioral correlates of prosociality thanks to well-controlled quantitative data and a task challenging macaques with social decisions that could produce positive or negative outcomes. Gaze and eye-blinking served as proxies of monkeys’ social motivation and affective bond. Mutual gaze was indeed found to correlate with prosocial decisions and with social grooming in the living space, and partner-dependent rudimentary empathy was revealed through eye blinking in prediction of other’s discomfort. Cronin’s letter (2) focuses on our methods and on the interpretation of social gaze. Cronin claims that direct eye contact in monkeys is necessarily threatening and that the … [↵][1]1To whom correspondence should be addressed. Email: duhamel{at}isc.cnrs.fr. [1]: #xref-corresp-1-1

Many chimpanzees throughout the world are housed in captivity, and there is an increasing effort to recreate social groups by mixing individuals with captive origins with those with wild origins. Captive origins may entail restricted rearing conditions during early infant life, including, for example, no maternal rearing and a limited social life. Early rearing conditions have been linked with differences in tool-use behavior between captive- and wild-born chimpanzees. If physical cognition can be impaired by non-natural rearing, what might be the consequences for social capacities? This study describes the results of network analysis based on grooming interactions in chimpanzees with wild and captive origins living in the Kumamoto Sanctuary in Kumamoto, Japan. Grooming is a complex social activity occupying up to 25% of chimpanzees' waking hours and plays a role in the emergence and maintenance of social relationships. We assessed whether the social centralities and roles of chimpanzees might be affected by their origin (captive vs wild). We found that captive- and wild-origin chimpanzees did not differ in their grooming behavior, but that theoretical removal of individuals from the network had differing impacts depending on the origin of the individual. Contrary to findings that non-natural early rearing has long-term effects on physical cognition, living in social groups seems to compensate for the negative effects of non-natural early rearing. Social network analysis (SNA) and, in particular, theoretical removal analysis, were able to highlight differences between individuals that would have been impossible to show using classical methods. The social environment of captive animals is important to their well-being, and we are only beginning to understand how SNA might help to enhance animal welfare.

Grooming handclasp (GHC) behaviour was originally advocated as the first evidence of social culture in chimpanzees owing to the finding that some populations engaged in the behaviour and others do not. To date, however, the validity of this claim and the extent to which this social behaviour varies between groups is unclear. Here, we measured (i) variation , (ii) durability and (iii) expansion of the GHC behaviour in four chimpanzee communities that do not systematically differ in their genetic backgrounds and live in similar ecological environments. Ninety chimpanzees were studied for a total of 1029 h; 1394 GHC bouts were observed between 2010 and 2012. Critically, GHC style (defined by points of bodily contact) could be systematically linked to the chimpanzee's group identity, showed temporal consistency both within and between groups, and could not be accounted for by the arm-length differential between partners. GHC has been part of the behavioural repertoire of the chimpanzees under study for more than 9 years (surpassing durability criterion) and spread across generations (surpassing expansion criterion). These results strongly indicate that chimpanzees' social behaviour is not only motivated by innate predispositions and individual inclinations, but may also be partly cultural in nature.

The formation of bonds between strangers is an event that occurs routinely in many social animals, including humans, and, as social bonds in general, they affect the individuals' welfare and biological fitness. The present study was motivated by an interest in the behavioural processes that drive bond formation in a social context of hostility, in which the incumbent partners vary greatly in physical power and reproductive interests, a situation in which individuals of many group-living species find themselves often throughout their lives. We focused on the quantitative analysis of female abductions via male aggressive herding in a nonhuman primate, the hamadryas baboon, in which intersexual bonds are known to be strong. We tested three hypotheses informed by sexual conflict/sexual coercion theory (male herding-as-conditioning and female grooming-as-appeasement) and by socioecological theory (unit size and female competition). The results supported the predictions: males resorted to coercive tactics (aggressive herding) with abducted females, and abducted females elevated the amount of grooming directed at their new unit males; in fact, they escaped from the otherwise negative effect of unit size on female-to-male grooming. These findings reveal that conflicts of interest are natural ingredients underpinning social bonds and that resorting to coercive aggression may be an option especially when partners differ greatly in their physical power.

Research in stress physiology has demonstrated the benefits of receiving social support during stressful conditions. However, recent data have shown that the efficacy of social support in buffering physiological and behavioral responses to stressor agents depends on species, sex, and relatedness among animals. This study investigated whether different kinds of social support (presence of same sex related or nonrelated conspecifics) have the same effect on hormonal (fecal cortisol levels) and behavioral responses (agonistic: scent-marking and individual piloerection; anxiety: locomotion; tension-reducing: autogrooming, allogrooming, and body contact). We used adult male and female isosexual dyads of Callithrix jacchus, a small Neotropical primate from the Callitrichidae family, widely used in the study of stress and related diseases. Following a 28-day baseline phase, dyads faced three challenging situations (phase 1: dyads were moved together from the baseline cage to a similar new cage; phase 2: each dyad member was moved alone to a new cage; and phase 3: dyad members were reunited in the same baseline cage). Type of social support was found to influence the response to stressors differently for each sex. Related male dyads did not change their hormonal or behavioral profile over the three experimental phases, when compared to the baseline phase. For nonrelated male dyads, social support buffered hormonal but not behavioral response. For females, the social support offered by a related and nonrelated animal, does not seem to buffer the stress response, as shown by correlations between agonistic behaviors versus cortisol and locomotion during all three experimental phases and a significant increase in fecal cortisol levels during phases 2 and 3, when compared with baseline levels. The results only partially support the buffering model theory and corroborate other studies reporting that the benefits of social support during a period of crisis arise only when it is adaptive for that species.

Grooming among nonhuman primates is widespread and may represent an important service commodity that is exchanged within a biological marketplace. In this study, using focal animal sampling methods, we recorded grooming relationships among 12 adult females in a free-ranging group of Tibetan macaques (Macaca thibetana) at Huangshan, China, to determine the influence of rank and kinship on grooming relationships, and whether females act as reciprocal traders (exchange grooming received for grooming given) or interchange traders (interchange grooming for social tolerance or other commodities). The results showed that: (1) grooming given was positively correlated with grooming received; (2) kinship did not exert a significant influence on grooming reciprocity; and (3) grooming reciprocity occurred principally between individuals of adjacent rank; however, when females of different rank groomed, females tended to groom up the hierarchy (lower ranking individuals groomed higher ranking individuals more than vice versa). Our results support the contention that both grooming reciprocity and the interchange of grooming for tolerance represent important social tactics used by female Tibetan macaques.

Reciprocation is thought to favour altruism among nonrelatives. Three types of reciprocity have been proposed: direct, indirect and generalized. All three are theoretically possible, but their role in real biological systems is unclear. We concurrently examined the occurrence of direct, indirect and generalized reciprocity during grooming exchanges in longtailed macaques, Macaca fascicularis. The occurrence of the grooming monkey A gave B predicted the latency and occurrence of the grooming B gave back to A (direct reciprocity), the latency of the grooming A received from C (indirect reciprocity), but not the grooming B gave C (generalized reciprocity). The duration of the grooming monkey A gave B predicted the latency and occurrence of the grooming B gave back to A (direct reciprocity) but not the grooming A received from C (indirect reciprocity) or the grooming B gave C generalized reciprocity). Finally, monkeys directed overall more of their grooming to those individuals that overall groomed them more (direct reciprocity), but not to those that groomed other individuals more (indirect reciprocity); nor did monkeys that received overall more grooming groom others more (generalized reciprocity). Overall, we found strong evidence for direct reciprocity, limited support for indirect reciprocity and no evidence for generalized reciprocity. Our results support the view that direct reciprocity plays a crucial role in the life of primates and suggest indirect and generalized reciprocity are rare or absent in nonhuman animals. We argue that direct reciprocity may be driven by a system of partner-specific emotional bookkeeping of past social interactions that does not require complex cognitive capacities.