Reconciliation and the Costs of Aggression in Wild Barbary Macaques (Macaca sylvanus): A Test of the Integrated Hypothesis

The ‘integrated hypothesis’ predicts that reconciliation (the post‐conflict friendly interaction between former opponents observed in various group‐living species) functions to reduce anxiety and the risk of aggression from the former opponent or a bystander in the aftermath of a conflict. It also predicts that relationship quality between opponents affects the occurrence of reconciliation and modulates the anxious response of the opponents after a conflict. Because of the asymmetric nature of aggressive interactions, the cost of aggression is likely to differ between the victim and the aggressor. The aim of this study was to test the predictions of the ‘integrated hypothesis’ independently for the victim and the aggressor of a conflict. We collected data on two wild groups of Barbary macaques. This study represents, to our knowledge, the first systematic test of the integrated hypothesis on wild, non‐provisioned animals. Victims of aggression were at a greater risk of receiving aggression from the former opponent or a bystander after a conflict and showed elevated anxiety. We found no such costs for the aggressor. Reconciliation reduced anxiety in the victim but did not reduce their risk of receiving aggression. Finally, relationship quality affected the occurrence of reconciliation but did not modulate post‐conflict anxiety. The results of our study show that the costs of aggression are asymmetrically distributed between the victim and the aggressor. Such differences are likely to lead to different social tactics used by the victim and the aggressor in the aftermath of a conflict.     

Grooming coercion and the post-conflict trading of social services in wild Barbary macaques

In animal and human societies, social services such as protection from predators are often exchanged between group members. The tactics that individuals display to obtain a service depend on its value and on differences between individuals in their capacity to aggressively obtain it. Here we analysed the exchange of valuable social services (i.e. grooming and relationship repair) in the aftermath of a conflict, in wild Barbary macaques (Macaca sylvanus). The relationship repair function of post-conflict affiliation (i.e. reconciliation) was apparent in the victim but not in the aggressor. Conversely, we found evidence for grooming coercion by the aggressor; when the victim failed to give grooming soon after a conflict they received renewed aggression from the aggressor. We argue that post-conflict affiliation between former opponents can be better described as a trading of social services rather than coercion alone, as both animals obtain some benefits (i.e. grooming for the aggressor and relationship repair for the victim). Our study is the first to test the importance of social coercion in the aftermath of a conflict. Differences in competitive abilities can affect the exchange of services and the occurrence of social coercion in animal societies. This may also help explain the variance between populations and species in their social behaviour and conflict management strategies.     

Postconflict Affiliation and Stress-Related Behavior of Long-Tailed Macaque Aggressors

Previous studies on macaques and baboons showed that after agonistic conflicts aggressees as well as aggressors show an increase in stress-related behavior such as scratching. Reconciliation reduces stress-related behavior of the aggressee. We investigated the influence of various affiliative postconflict behaviors of the aggressor on the aggressor's scratching rates in captive long-tailed macaques: reconciliation, contacts with the aggressee's kin (or substitute reconciliation), and contact with other group members (or triadic affiliation). After a conflict, the aggressor showed an increase in rates of scratching. Scratching rates were reduced after reconciled conflicts compared to nonreconciled conflicts. Substitute reconciliation did not reduce scratching when we controlled for the influence of reconciliation, i.e., the aggressor might not interpret it as a substitute for reconciliation. Triadic affiliation did not reduce scratching rates, hence, triadic affiliation probably does not console the aggressor. Scratching rates after reconciliation are significantly lower than scratching rates after triadic affiliation. This proves that the stress-reducing effect of reconciliation is not due to the calming effect of general body contact but that the stress reduction is specifically associated with contacts with the former opponent. The contestants are anxious about their relationship, and only reconciliation takes away this anxiety. Reconciliation is thus an important social repair strategy.     

Canine Reconciliation and Third‐Party‐Initiated Postconflict Affiliation: Do Peacemaking Social Mechanisms in Dogs Rival Those of Higher Primates?

Conflicts over food, access to mates, or other limited resources can sometimes escalate into aggression. In species that form social groups, these aggressive conflicts can jeopardize the benefits of group living, such as enhanced access to valued resources, necessitating the development of behavioural mechanisms that either mitigate conflicts, prevent aggressive escalation or resolve disputes. Two important mechanisms for managing the effects of disputes involve postconflict (PC) affiliative behaviour, either between the former opponents (called ‘reconciliation’) or between one opponent and a third party. Even though numerous studies have tested reconciliatory and third‐party affiliation tendencies in primates, for non‐primate animals little systematic data are available. We performed behavioural observations on three groups of captive domestic dogs (Canis familiaris) and used a PC/MC method to test the existence of reconciliation and third‐party affiliation in this species. The results of this study clearly indicate that both reconciliation and third‐party PC interactions are present in the domestic dog, and form important social mechanisms of the domestic dog. Furthermore, familiar individuals showed a significantly higher proportion of reconciled conflicts than did unfamiliar individuals, and also displayed fewer conflicts. Finally, we show that most of the third‐party affiliations involve the victim of a conflict and that victim‐directed affiliation outweighs victim‐initiated third‐party affiliation in these PC interactions.     

Postconflict Affiliation of Aggressors in <Emphasis Type="Italic">Papio hamadryas</Emphasis>

Researchers have associated variation in the occurrence of postconflict behaviors with variation in the relationship quality between involved individuals. Apart from those on the great apes, the vast majority of postconflict studies involved female-bonded species and focused on the victim. We examined postconflict affiliation involving the aggressor in a non-female-bonded species, hamadryas baboons (Papio hamadryas), and investigated the influence of relationship quality on the occurrence of 2 types of postconflict affiliative behaviors. Hamadryas baboons reconciled after a conflict and the highest rate of reconciliation was between one-male unit (OMU) leader males and their females. Via direct measures of relationship characteristics we also found that partners with higher-quality relationship, e.g., highly affiliative dyads and allies, showed higher levels of conciliatory tendency than dyads with lower-quality relationship, e.g., less affiliative dyads and non-allies. We found evidence of postconflict third-party affiliation initiated by aggressors, but not by third parties. Further, aggressor-initiated affiliation was more likely with individuals of the same OMU and individuals with which the aggressor maintained a strongly affiliative relationship. Our findings provide further support for relationship quality as a fundamental underlying factor not only in reconciliation, but also in postconflict affiliations involving third parties.     

Testing the function of reconciliation and third-party affiliation for aggressors in hamadryas baboons (Papio hamadryas hamadryas)

In social groups, agonistic conflicts can have different negative consequences. Several post-conflict interactions have been suggested as post-conflict management behaviors to mitigate those negative effects. In this study, we investigated the function of two post-conflict behaviors--reconciliation and aggressor-initiated third-party affiliation--on the aggressor's levels of post-conflict anxiety and aggression in a large colony of hamadryas baboons. We also examined variation in the aggressor's levels of post-conflict anxiety as a function of relationship quality between the opponents as predicted by the Integrated Hypothesis. We found that after conflicts hamadryas baboon aggressors showed increased rates of anxiety-related behaviors and that they were also more likely to be involved in renewed aggressive interactions. Although both reconciliation and aggressor-initiated third-party affiliation reduced the probability of receiving post-conflict aggression, only reconciliation reduced the rates of anxiety-related behaviors, suggesting that the aggressors' post-conflict anxiety might be owing mainly to the damage that the conflict causes to their relationship with the victim. Furthermore, aggressor's rates of post-conflict anxiety were higher after conflicts with individuals with whom they had a high-quality relationship, supporting the idea that levels of post-conflict anxiety mediate the occurrence of reconciliation depending on the quality of the relationship with former opponent as predicted by the Integrated Hypothesis.     

Functions of post‐conflict affiliation with a bystander differ between aggressors and victims in Japanese macaques

Post‐conflict affiliative interactions with a bystander, an uninvolved third party, have been reported in several species. The functions of these interactions could vary depending on whether the individual was an aggressor or a victim in a conflict. We examined the occurrence of and three potential functions for bystander affiliation—substitute for reconciliation, self‐protection and consolation (stress reduction)—in a free‐ranging group of Japanese macaques. We predicted that in this despotic species, the function of bystander affiliations for victims was self‐protection, whereas this was not so for aggressors. We found that compared to control situations, both aggressors and victims engaged in bystander affiliation soon after a conflict, confirming the occurrence of bystander affiliation. Victims were less likely to receive further aggression when bystander affiliation occurred than when no such interaction occurred, consistent with the explanation that post‐conflict bystander affiliation functions as self‐protection for victims. Aggressors were less likely to perform self‐scratching, an indicator of post‐conflict stress, when bystander affiliation occurred. This suggests that such affiliations benefited aggressors by reducing stress. Self‐scratching was not less frequent after affiliation with a bystander who was familiar with the former opponent, indicating that substitute reconciliation did not apply for either aggressors or victims. When bystander affiliation occurred, the bystander was a more familiar individual for aggressors and victims than the former opponent was. In conclusion, aggressors benefited in stress reduction, whereas victims benefited in self‐protection through affiliation with bystanders with whom they have a good relationship. Our study indicated that monkeys cope with post‐conflict problems according to their roles or situations not only by reconciliation but also by bystander affiliation.     

Affiliation Between Aggressors and Third Parties Following Conflicts in Long-Tailed Macaques (Macaca fascicularis)

Studies on cercopithecine monkeys have shown that soon after an agonistic conflict, victims have increased rates of affiliation with the agressor—reconciliation—but not with other group members. Postconflict affiliation is thought to function to restore disturbed relationships and to reduce social tension. This study on a captive group of long-tailed macaques (Macaca fascicularis) is focused on postconflict affiliative behavior of the aggressor. Increased rates of contact between female aggressors and kin of the victim occurred, as well as between female aggressors and their own kin. Furthermore, there were increased rates of contact between aggressors—males and females—and other group members. The increase in contacts with the victim's kin was selective, i.e., it could not be ascribed to the increased contact tendency with group members in general, and was not a side effect of the aggressor's proximity to the victim due to reconciliation. The increase in contacts with own kin was not selective. The fact that male aggressors do not have increased postconflict contacts with their kin or with kin of the victim is in agreement with the notion that males are less integrated in the nepotistic matrilineal network than females are. The fact that studies by others that focused on the victim evidence no increase in postconflict contacts with kin of the opponent or with other group members may be explained by the aggressor's larger influence over the postconflict situation: to reduce social tension, it might be more effective to affiliate with the aggressor than with the victim. Our findings emphasize that conflicts influence the behavior of other monkeys besides the direct contestants and, thus, indicate that the disturbance of social homeostasis is a matter of concern for all group members.     

Post-Conflict Affiliation in Barbary Macaques is Influenced by Conflict Characteristics and Relationship Quality, but Does Not Diminish Short-Term Renewed Aggression

Many group living primates have evolved mechanisms to repair their social relationships after conflicts ('reconciliation'). We analysed the post-conflict behaviour of female Barbary macaques, Macaca sylvanus , living in the enclosure 'La Forêt des Singes' at Rocamadour, France. Based on a sample of 914 conflicts, we investigated whether relationship (kinship, rank, affiliation, support and sex) and conflict characteristics (conflict intensity, context and duration) affected the quality and frequency of affiliative post-conflict interactions. Thirty-two per cent of all conflicts were followed by post-conflict affiliation. Rates of socio-positive interactions and support were better predictors of post-conflict affiliation than kinship or rank. Short conflicts were followed by post-conflict affiliation relatively more frequently, after a shorter latency, but only briefly, and such interactions were initiated by both parties equally frequently. The majority of affiliative post-conflict interactions occurred immediately after the end of the conflict. In sum, female Barbary macaques invest more in post-conflict affiliation with valuable partners, and they modulate their post-conflict behaviour in relation to conflict characteristics. Remarkably, affiliative post-conflict interactions increased the short-term probability of renewed aggression by the former aggressor to 16% compared with 9% for conflicts that were not followed by affiliative behaviour. Such renewed aggression after post-conflict affiliation occurred particularly frequently among females and after conflicts over food, suggesting that post-conflict affiliation sometimes falsely lures the former victim to stay in the vicinity, even at the risk of receiving renewed aggression.     

Postconflict Behavior of Spectacled Leaf Monkeys (Trachypithecus obscurus). I. Reconciliation

Studies of postconflict behavior have focused on Old World primates, particularly on members of the cercopithecines and chimpanzees. We present data on patterns of reconciliation in two captive groups of spectacled leaf monkeys, members of the Colobinae. Reconciliation occurred at a high rate relative to that in other primate species and within the first minute following a conflict. Friendly postconflict contact was usually initiated by aggressors in one group, and by recipients in the other. But, there was no difference in postconflict initiative to contact in comparison with MCs. These two groups showed behavioral specificity in the context of postconflict reunions. Ventroventral embracing was a common, explicit (de Waal, 1993) form of reconciliation. The intensity of aggression and situations in which the victim responded aggressively had no effect on the likelihood of reconciliation occurring. The postconflict behavior of both groups lends further support to the relationship-quality hypothesis (Aureli et al., 1989). Kinship and rank distance and had no effect on reconciliation, though affiliation levels correlated positively with the tendency to reconcile. These results indicate that spectacled langurs are among the more tolerant of the species studied so far.     

Postconflict third-party affiliation in rooks, Corvus frugilegus

Conflict features in the lives of many animal species and induces social stress mediated by glucocorticoid hormones [1]. Postconflict affiliation, between former opponents (reconciliation) or between former opponents and a bystander (third-party affiliation), has been suggested as a behavioral mechanism for reducing such stress [2], but has been studied almost exclusively in primates [3]. As with many primates, several bird species live in social groups and form affiliative relationships [4]. Do these distantly related animals also use affiliative behavior to offset the costs of conflict? We studied postconflict affiliation in a captive group of rooks. Unlike polygamous primates, monogamous rooks did not reconcile with former opponents. However, we found clear evidence of third-party affiliation after conflicts. Both initiators and targets of aggression engaged in third-party affiliation with a social partner and employed a specific behavior, bill twining, during the postconflict period. Both former aggressors and uninvolved third parties initiated affiliative contacts. Despite the long history of evolutionary divergence, the pattern of third-party affiliation in rooks is strikingly similar to that observed in tolerant primate species. Furthermore, the absence of reconciliation in rooks makes sense in light of the species differences in social systems.     

Postconflict Behavior of Spectacled Leaf Monkeys (Trachypithecus obscurus). II. Contact with Third Parties

We studied the postconflict interactions with group members other than the former opponent in two groups of spectacled leaf monkeys. We found no evidence of redirection of aggression towards other group members. Victims and aggressors sought affiliative contacts with uninvolved third parties. There was no evidence for consolation—affiliative contact initiated by an uninvolved third party, directed towards victims of aggression—in either group when all affiliative behaviors were considered. However, embracing was a characteristic first-contact interaction between individuals involved in aggression and third parties. This finding mirrors the results concerning reconciliation in spectacled leaf monkeys. Accordingly, embracing may be a true consolatory behavior in this species. When contacts with third parties occurred before or in the absence of reconciliation, the timing of such contacts fell within the time window during which reconciliation normally occurs. These contacts also resulted in affiliation levels twice that of baseline levels, supporting the idea that these contacts may function as a form of substitute reconciliation. We discuss these results in light of recent theories concerning postconflict behavior in primates.     

The Occurrence of Postconflict Skills in Captive Immature Chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>)

Conflict management strategies can reduce costs of aggressive competition in group-living animals. Postconflict behaviors such as reconciliation and third-party postconflict affiliation are widely accepted as social skills in primates and have been demonstrated in many species. Although immature primates possess a repertoire of species-specific behaviors, it is thought that they gradually develop appropriate social skills throughout prolonged juvenility to establish and maintain complex social relationships within their group. We examined the occurrence of postconflict skills in five immature chimpanzees (Pan troglodytes) over 15 mo, focusing on interactions that were not with the subject’s mother. We observed reconciliation, with conciliatory tendencies comparable to adults, and provide the first evidence that captive immature chimpanzees commonly reconciled using social play. However, immatures were not more likely to reconcile valuable than nonvaluable relationships. We also observed third party postconflict affiliation although at a lower level than reported for adults. Our results provide evidence for postconflict skills in immature chimpanzees but the lack of higher conciliatory tendency with valuable partners and low occurrence of third-party affiliation indicates extended juvenility may be required refine these skills. Further work is needed to investigate whether these behaviors have the same function and effectiveness as those found in adults.     

The Function and Determinants of Reconciliation in <Emphasis Type="BoldItalic">Pan troglodytes</Emphasis>

Reconciliation (the postconflict affiliative reunion between former opponents) may mitigate costs of aggressive conflict by repairing the opponents’ relationship and reducing stress. We showed that postconflict levels of self-directed behavior were lower after reconciliation than when reconciliation did not occur in chimpanzees (Pan troglodytes) at Chester Zoo, providing support for a stress-alleviating function for reconciliation. Further, we investigated the effects of multiple factors on the occurrence of reconciliation using generalized linear mixed models. We performed 2 separate analyses, a “traditional” analysis and a “targeted” analysis. The former included variables previously used to assess the occurrence of reconciliation in primates, i.e., conflict characteristics, sex combination, and a simple measure of relationship value. The latter included species-specific variables such as the occurrence of consolation (postconflict affiliation from a bystander to the recipient of aggression); initiation of the conflict with a bluff display; and measures of relationship value, compatibility, and security specific to the study group. Whereas the traditional analysis showed that female-female dyads and valuable partners were most likely to reconcile, the targeted analysis showed that reconciliation was less likely to occur when consolation took place or when aggression was initiated with bluff displays. Further analyses revealed that the effect of sex-combination on reconciliation was due to its intercorrelation with bluff display. This study highlights the importance of considering variables specific to the study species and group when investigating the determinants of reconciliation and warns against premature interpretation of results without due consideration for all other possible determinants.     

Postconflict social interactions among barbary macaques (Macaca sylvanus)

We investigated the occurrence of postconflict social interactions in a group of Barbary macaques (Macaca sylvanus)that live in a large enclosure. We collected data during the mating and the nonmating seasons and analyzed them via two methods. Separate analyses for the two seasons yielded very similar results. Reconciliation and redirection occurred. But we found no evidence for consolation and postconflict kin-oriented affiliation. The consistency of these findings with those on other species of Macacaindicates that reconciliation and redirection are typical postconflict social interactions of macaque victims.     

Post-Conflict Anxiety in Japanese Macaques (Macaca fuscata): Aggressor's and Victim's Perspectives

The aim of this study was to investigate the short‐term consequences of aggression in socially living Japanese macaques (Macaca fuscata) focusing on the emotional response of both aggressors and victims of aggression. Both individuals involved showed an increase in the rate of scratching (a behavioural indicator of anxiety) in the minutes following the aggressive confrontation. Such increase was larger in victims than in aggressors. Multivariate analyses of the factors modulating post‐conflict scratching showed that for both the aggressor and the victim the main predictor of post‐conflict scratching was its opponent’s post‐conflict scratching. These results suggest both opponents shared the same perception of the consequences of aggression, and responded with similar emotional arousal.     

Postconflict Affiliation Between Former Opponents in Macaca thibetana on Mt. Huangshan, China

We describe basic patterns of postconflict affiliation between former opponents within a group of wild, provisioned Tibetan macaques Macaca thibetana on Mt. Huangshan, China. Like most primates studied to date, Tibetan macaques reconciled, i.e., overall they engaged in affiliative interaction with opponents at higher rates immediately after an aggressive conflict than at other times. Probabilities of affiliation were enhanced ≤30 s after the end of hostilities. However when we examined sex partner combinations separately, we found unequivocal evidence for reconciliation only for male-male dyads. Tolerant interaction among other partner combinations apparently was not disrupted after a conflict, presumably obviating the need to reconcile. One aspect of reconciliation among males was consistent with other indications of a despotic dominance style: aggressors initiated a higher proportion of affiliative interactions after a conflict than at other times. Another aspect of reconciliation was more typical of relaxed dominance styles: males used specialized behaviors (embraces and same-sex mounts) disproportionately to reconcile. We also found inconsistent evidence for the valuable relationship hypothesis; probabilities of reconciliation were enhanced for male-male dyads with the closest affiliative relationships, but not for those that displayed the most tolerance or mutual agonistic support. We discuss reconciliation and other aspects of conflict management among males in the context of a group with nearly even sex ratios and high male-male mating competition.     

Postconflict behavior in captive western lowland gorillas (Gorilla gorilla gorilla)

Postconflict (PC) behaviors, including reconciliation and consolation, have been observed in many primate and several nonprimate species. Using the PC-matched control (MC) method, PC behavior was examined in two groups (n=13) of captive western lowland gorillas, a species for which no conflict resolution data have been published. Analyses of 223 conflicts showed significantly more affiliation between former opponents after a conflict when compared to control periods, indicating reconciliation. Results also showed significantly more affiliation between the victim and a third-party after a conflict, indicating consolation. Both solicited and unsolicited consolation were observed. The majority of the affiliative interactions observed for both reconciliation and consolation were social proximity, which suggests that unlike most nonhuman primates, proximity, rather than physical contact, may be the main mechanism for resolving conflicts in western lowland gorillas. PC behavior was not uniform throughout the groups, but rather varied according to dyad type.     

Conflict resolution following aggression in gregarious animals: a predictive framework

Knowledge of how animals manage their conflicts is critical for understanding the dynamics of social systems. During the last two decades research on gregarious animals, especially primates, has focused on the mechanisms of conflict management, mainly on friendly postconflict reunions (also called ‘reconciliation’) in which former opponents exchange affiliative behaviour soon after an aggressive conflict. Our aim in this paper is to present a framework in which the costs and benefits of friendly postconflict reunions, both for each individual opponent and for their mutual relationship, are used to predict the patterning of postconflict resolution mechanisms in other gregarious animals. The framework predicts the occurrence of postconflict reunions in species that live in stable social units, have individualized relationships, and experience postconflict hostility, but especially in those in which intragroup aggression disrupts valuable relationships. The critical issue is whether aggressive conflicts occur between cooperative partners and whether the level of aggression is sufficient to jeopardize the benefits associated with such valuable relationships. We conclude by proposing four research priorities to evaluate the role of friendly reunions in negotiating relationships and the way they are themselves influenced by asymmetries in partner value and biological market effects. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Reciprocation and interchange of grooming,agonistic support,feeding tolerance,and aggression in semi‐free‐ranging Barbary macaques

Evidence from a range of primate species indicates that grooming can be exchanged either for itself or for other rank‐related “commodities,” such as agonistic support, feeding tolerance, or reduced aggression. Patterns of exchange behavior have been found to vary considerably between species, and understanding the causes of this variation is central to the study of the evolution of primate social systems. It is, therefore, essential that exchange behavior is examined in a wide range of species and settings. This article is the first to explore the reciprocation and interchange of grooming in the Barbary macaque (Macaca sylvanus). We collected focal data on semi‐free‐ranging adult female Barbary macaques at Trentham Monkey Forest, England, and analyzed dyadic data using Generalized Linear Mixed Models. We found evidence for the reciprocal exchange of grooming and for the interchange of grooming for agonistic support and tolerance while feeding. There was no evidence that grooming was traded for a reduction in aggression; indeed, we found a positive relationship between aggression given and grooming received. This may reflect the “extortion” of grooming from subordinates by dominant animals. These results will facilitate comparative analyses of exchange behavior by adding to the current database a new species, characterized by a different social style from those macaque species previously investigated. Am. J. Primatol. 73:1127–1133, 2011. © 2011 Wiley Periodicals, Inc.