Following the rules: why small groups of tamarins do not reconcile conflicts

Reconciliation is the post-conflict friendly reunion between opponents. A series of conditions and rules in order for reconciliation to take place has been recently proposed. One critical condition is that the relationship between opponents must be disrupted. We tested this condition using post-conflict and matched-control observations on 4 small groups of tamarins (Saguinus labiatus). Our previous lack of evidence for reconciliation was confirmed. No post-conflict relationship damage was therefore expected. We found evidence that relationships were disturbed following conflicts over food but, as in other primates, no evidence for reconciliation following such conflicts was found. For non-food-related conflicts there was no evidence that relationships were disturbed, as opponents were in close proximity to each other and resumed the exact same activity as frequently in the post-conflict observations as they did in the matched-control observations. We conclude that 'everyday' aggression may not disrupt the relationships among individuals from the same family group and therefore reconciliation is not needed.     

Anxiety Level Predicts Post-Conflict Behaviour in Wild Japanese Macaques (Macaca fuscata yakui)

Reconciliation (i.e. the post-conflict exchange of friendly behaviour between former opponents) functions to control for the detrimental effects that aggression may have on social relationships. Studies conducted so far have investigated intra-individual sources of variation in post-conflict behaviour, showing that animals have a stronger increase in anxiety and are more likely to reconcile after conflicts with valuable partners, such as kin. Much less attention has been given to how differences between individuals in emotional profiles affect post-conflict behaviour. Our aim was to analyse whether inter-individual differences in baseline anxiety levels predicted the magnitude of the increase in anxiety following a conflict and the occurrence of reconciliation. We collected data on two groups of wild Japanese macaques ( Macaca fuscata yakui ). Animals having a higher baseline level of anxiety had a more dramatic anxious response following a conflict while controlling for a series of factors (e.g. relationship quality between opponents). These more anxious animals were also less likely to reconcile than more relaxed individuals. Therefore, more anxious animals face some social costs by being less able to cope with the post-conflict condition. We propose that differences in anxiety levels may be interpreted as tradeoffs between benefits and costs across conditions. For example, more anxious animals, who are less able to reconcile conflicts, might also be less exploratory and thus face a lower risk to eat unknown, poisonous food.     

Patterns of reconciliation among captive gelada baboons (Theropithecus gelada): A brief report

Animals that live in groups are frequently exposed to conflict situations and must in some way maintain group cohesion. One mechanism that appears to restore social relationships after they have been disrupted by conflict isreconciliation. This study investigated reconciliatory behavior in the gelada baboon,Theropithecus gelada. The subjects were 11 adult geladas, housed in a large outdoor enclosure at the Bronx Zoo/Wildlife Conservation Park, New York. Five-minute focal animal samples following spontaneous aggression were compared with 5-min matched-control samples. The results of this study were: (1) geladas reunited in a friendly way after aggression; (2) former opponents were attracted to one another rather than dispersed from one another after a conflict; (3) most post-conflict reunions occurred within the first 2 min of the post-conflict period; and (4) geladas do not have any specific types of behavior associated with post-conflict reunions as do chimpanzees and macaques. The results of this study support the hypothesis that gelada baboons reconcile after aggression.     

Conflict and postconflict behaviour in captive black-and-white snub-nosed monkeys (<Emphasis Type="Italic">Rhinopithecus bieti</Emphasis>)

Black-and-white snub-nosed monkeys (Rhinopithecus bieti) have almost never been the subject of any behavioural observations in captivity. This study was aimed at providing preliminary information about agonistic and reconciliation behaviour in a group kept at the Kunming Institute of Zoology in China. Established procedures were used for this investigation (i.e., the postconflict/matched-control method and the time-rule method). Intra-group aggression rates were quite low. Postconflict affiliation as well as selective attraction of former opponents to each other following conflicts was demonstrated. Former opponents contacted each other earlier in postconflict periods than in matched-control periods. The average conciliatory tendency of all focal individuals combined was 54.5%. After an agonistic interaction, the first affiliative contact between former aggressors usually took place within the first minute. The behaviours most often shown as first affiliations after a conflict were body contact, mount, touch, and hold-lumbar, of which the latter is an explicit reconciliatory gesture. Furthermore, the adult male intervened non-aggressively in 84% of all conflicts (n=25) among the adult females. Overall, the patterns of aggression and reconciliation observed in R. bieti bear many of the traits that characterise tolerant primate species.     

Ravens reconcile after aggressive conflicts with valuable partners

Reconciliation, a post-conflict affiliative interaction between former opponents, is an important mechanism for reducing the costs of aggressive conflict in primates and some other mammals as it may repair the opponents' relationship and reduce post-conflict distress. Opponents who share a valuable relationship are expected to be more likely to reconcile as for such partners the benefits of relationship repair should outweigh the risk of renewed aggression. In birds, however, post-conflict behavior has thus far been marked by an apparent absence of reconciliation, suggested to result either from differing avian and mammalian strategies or because birds may not share valuable relationships with partners with whom they engage in aggressive conflict. Here, we demonstrate the occurrence of reconciliation in a group of captive subadult ravens (Corvus corax) and show that it is more likely to occur after conflicts between partners who share a valuable relationship. Furthermore, former opponents were less likely to engage in renewed aggression following reconciliation, suggesting that reconciliation repairs damage caused to their relationship by the preceding conflict. Our findings suggest not only that primate-like valuable relationships exist outside the pair bond in birds, but that such partners may employ the same mechanisms in birds as in primates to ensure that the benefits afforded by their relationships are maintained even when conflicts of interest escalate into aggression. These results provide further support for a convergent evolution of social strategies in avian and mammalian species.     

Effect of valuable relationship on reconciliation and initiator of reconciliation in captive bottlenose dolphins (<Emphasis Type="Italic">Tursiops truncatus</Emphasis>)

Reconciliation, post-conflict affiliation between former opponents, was suggested to repair the relationship between former opponents. The number of times that each former opponent initiates reconciliation may be affected by the dominance style. Despotic dominance style was suggested to restrain the initiation of reconciliation by recipients of aggression, unlike relaxed dominance style. Although reconciliation was suggested to restore relationships, reconciliation sometimes did not occur. The valuable relationship hypothesis predicts that reconciliation is more likely to occur when former opponents share a valuable relationship. However, few studies have tested this hypothesis in non-primate species. This study investigated, in captive bottlenose dolphins, which are suggested as having a relaxed dominance style, whether aggressors or recipients of aggression initiate reconciliation, and whether relationships between former opponents affect the occurrence of reconciliation. The number of times that aggressors or recipients of aggression initiate reconciliation did not differ. Recipients of aggression initiated reconciliation sooner than aggressors. These results support the prospect that recipients of aggression are not impeded in initiating reconciliation in relaxed species. Former opponents who share a more affiliative relationship were reconciled more frequently. Bottlenose dolphins were suggested to receive the benefits from individuals who shared more affiliative relationships. The valuable relationship hypothesis may be supported in bottlenose dolphins.     

Post-conflict Social Events in Wild Mountain Gorillas (Mammalia,Hominoidea). I. Social Interactions between Opponents

Researchers have documented elevated rates of affinitive interaction between opponents shortly after aggressive conflicts, or reconciliation, in many primate species. Reconciliation may ameliorate the immediate negative effects of aggression by reducing the chance of further aggression between opponents and thus reducing tension, and may avert or repair damage to long-term social relationships important to the animals' fitness. Data on post-conflict interactions between opponents in two groups of wild mountain gorillas (Gorilla gorilla beringei) fail to show reconciliation after conflicts between females, between males, or between immatures, but females seem to commonly reconcile themselves with males after receipt of male aggression. Females and subordinate males often avoid same-sex opponents after conflicts. Females commonly retaliate against female aggressors, and post-conflict rates of aggression between females are higher than baseline levels. Females may not need to achieve reconciliation with each other because relationships between co-resident relatives are resiliant, while those between non-relatives are mostly neutral to antagonistic. Males are, however, important social partners and protectors of females, and female transfer is common. Thus, the results strongly support the ‘important relationships’ hypothesis for the function of reconciliation.     

Comparison of the Reconciliation Behavior of Stumptail and Rhesus Macaques

Observations were made following spontaneous aggressive incidents in a breeding group of captive stumptail macaques (Macaca arctoides). Participants were observed both during the first 10 min following the aggressive incident, and during matched-control observations. Data on 670 pairs of former opponents were collected, and compared with a sample of 573 such pairs of rhesus macaques (M. mulatta), which had been observed with identical methods in a previous study. Selective attraction between opponents was confirmed for the stumptail monkeys, i.e. both the absolute and the relative rate of nonagonistic body contact between individuals increased after aggression between them. The species was found to be considerably more conciliatory than rhesus monkeys, and to have a remarkably rich repertoire of reassurance gestures. The most characteristic conciliatory behavior is the hold-bottom ritual, in which one individual (usually the subordinate) presents its hindquarters, and the other (usually the dominant) clasps the other's haunches. The high rate of reconciliation among stumptail monkeys extended to all relationship classes, and a correlation with the closeness of social bonds (measured as time spent in association) could not be demonstrated. Because of the generality of the species' high peacemaking tendencies it is assumed that group cohesiveness is of great survival value in the wild.     

Kin-mediated reconciliation substitutes for direct reconciliation in female baboons

It has been hypothesized that group-living mammals engage in reconciliation (post-conflict affiliation between former opponents) to reduce the disruptive costs of aggression and restore opponents' tolerance to baseline levels. Recipients of aggression are sometimes reluctant to tolerate the proximity of a recent opponent, however, in apparent fear that aggression will be renewed. In such cases, reconciliatory behaviour by the aggressor's close kin may substitute for direct reconciliation. We describe a playback experiment with free-ranging baboons (Papio hamadryas ursinus) that examines whether friendly behaviour by the aggressor's kin can substitute for direct reconciliation by the aggressor herself. In the test condition, female subjects who had recently been threatened heard the friendly grunt of one of their aggressor's relatives, mimicking kin-mediated vocal reconciliation. In the control condition, subjects heard the grunt of a dominant female from a different matriline. Subjects responded significantly more strongly in test than in control trials. Moreover, in the next hour they were significantly more likely to tolerate the proximity of both their aggressor and the relative whose grunt they had heard. In contrast, subjects' behaviour towards both control females and other members of their aggressor's matriline was unaffected. We conclude that kin-mediated vocal reconciliation can substitute for direct reconciliation in baboons.     

Resolution of aggressive conflicts by immature long-tailed macaques Macaca fascicularis

The behaviour following aggressive interactions differed from the behaviour following friendly or neutral control interactions among unrelated immature male Macaca fascicularis. Former opponents interacted again sooner and more often after aggression than after a friendly or neutral encounter. The higher rate did not reflect a general increase in social activity. The behaviour characterizing encounters between former opponents also differed in the two situations, with more affiliative interactions postconflict. In both situations, however, most interactions between former opponents were initiated by the higher-ranking aggressor. This pattern of interactions between former opponents is interpreted as a repair mechanism for relationships strained by aggression (i.e. reconciliation). A similar pattern of interactions was found for related animals, though it occurred more rarely than among non-kin.     

Post-conflict Behaviour of Wild Olive Baboons. II. Stress and Self-directed Behaviour

Previous studies indicate that the proximate function of post-conflict affiliative interaction among primates is to reduce a victim's uncertainty about its opponent's future behaviour: the ‘uncertainty reduction hypothesis’ (Aureli & van Schaik 1991; Ethology, 89 , 101–114). This study confirms and extends these results, demonstrating that they are neither a product of captivity nor specific to macaques: both victims and initiators of aggression in a large group of wild olive baboons exhibited elevated rates of self-directed behaviour (SDB) - scratching, autogrooming, body-shaking and yawning - in a 10-min post-conflict period. During this period, they were more likely to receive further aggression. Reconciliation reduced both SDB and the incidence of further aggression. However, reconciliation only reduced SDB among individuals involved in conflicts in which both parties exchanged aggression. It is suggested that aggressors in unilateral conflicts were aroused rather than uncertain and that their victims' lack of control over post-conflict interactions (which tended to be initiated by their opponents) prevented them from benefiting from reconciliation in the same fashion as longtailed macaque victims, which frequently initiated reconciliation.     

Reconciling conflicts in a one-male society: the case of geladas (<Emphasis Type="Italic">Theropithecus gelada</Emphasis>)

Animals derive benefits from living in social groups but sociality also has its costs in that animals must compete with others for resources and mating opportunities. To cope with the conflict aftermath and social damage caused by competitive aggression, several group-living species use a variety of peace-keeping strategies. The affinitive post-conflict reunion of former opponents, defined as reconciliation, is the primary peace-keeping mechanism. In this study, we provide evidence for the occurrence of reconciliation and test some hypotheses on this post-conflict mechanism in geladas (Theropithecus gelada), a species often neglected in the study of post-conflict dynamics. The conciliatory contacts were uniformly distributed across the different sex–class combinations. Different from baboons, geladas did not show any particular kind of affinitive reconciliation behaviour. Notwithstanding the presence of a linear hierarchy, the dominance relationships did not affect the reconciliation dynamics. According to the valuable relationship hypothesis, coalitionary support seems to be a good predictor for a high level of conciliatory contacts. Finally, at an immediate level reconciliation plays a role in reducing renewed attacks by aggressors, which sought conciliatory contact more frequently than victims. In conclusion, even though the study of post-conflict behaviour in geladas needs to be continued, the patchy nature of their social network is a good model for testing some of the theoretical assumptions about primate conflict resolution.     

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.     

The ontogeny of sex differences in the behavior of patas monkeys

Many studies of sex differences in primates have been based on small experimental groups of peers in which only a limited range of social behavior could be expressed. In addition, the first few months of life are often the focus of such studies, with relatively little attention paid to older juveniles. In this study, 11 male and 9 female juvenile patas monkeys, living in a captive social group with all age-sex classes available, were observed between 1 and 4 years of age. A subset of seven patas monkeys was also observed between birth and 1 year of age. Here, we report the development of sex differences in independence, play, grooming, positioning behavior, and aggression over the juvenile period. Juvenile male patas monkeys played more and in longer bouts than females, but wrestling (rough-and-tumble play) was not more common among males. There were few differences in behaviors directed to male and female juveniles by other group members. Distinct differences emerged only in the behaviors of the juveniles themselves, with females being more active participants in social and aggressive interactions than males. In general, sex differences in patas monkeys show a mixture of patterns, some of which are predictive of adult sex differences and some of which appear to be specific to the particular demands of the juvenile period in this species     

Reconciliation in the Spotted Hyena (Crocuta crocuta)

Theory predicts that it should often be in the best interests of gregarious animals to repair social bonds damaged by within-group conflict. Indeed, reconciliation in many primates takes the form of affiliative behavior occurring shortly after a conflict. Here we inquired whether reconciliation also occurs among spotted hyenas ( Crocuta crocuta ), gregarious carnivores whose social lives share much in common with those of cercopithecine primates. In a large group of free-living hyenas in Kenya, we used focal animal observations to monitor rates at which various affiliative behaviors occurred before and after dyadic aggressive interactions. An affiliative behavior was identified as having a conciliatory function only if it occurred more frequently after than before fights, and if it was also associated with reduced rates of aggression between former opponents during the post-conflict interval. Of all affiliative behaviors monitored, only two types satisfied both these criteria: greeting behavior and non-aggressive approach. Over 72% of conciliatory behaviors occurred within the first five minutes after a fight, and hyenas reconciled after 14.6% of 698 fights. Mean conciliatory tendency (CT) for individual hyenas was 11.3%. Hyenas exhibited higher CTs when they were recipients (victims) of aggression than when they were aggressors, and they showed higher CTs in interactions with non-kin than with kin. Conciliatory tendencies did not vary with age–sex classes of opponents or with rank distance between opponents . Conciliatory tendency in spotted hyenas fell at the low end of the CT range observed among primates.     

Despotic wild patas monkeys (Erythrocebus patas) in Kala Maloue, Cameroon

The socio-ecological model predicts that the quality, distribution, and patch size of food resources determines the dominance hierarchy of female monkeys based on the type of food competition they experience. Comparative studies of closely related species have evaluated the socio-ecological model and confirmed its validity. For example, female patas monkeys in Laikipia, Kenya, form a nonlinear and unstable dominance hierarchy (i.e., egalitarian), whereas females of sympatric, closely related savannah monkeys form a linear and stable dominance hierarchy (i.e., despotic), in accordance with the model's predictions of the characteristics of food resources. I compared agonistic interactions involving food between patas monkeys (Erythrocebus patas) and sympatric savannah monkeys (Cercopithecus aethiops) in Kala Maloue, Cameroon. I found linear dominance hierarchies not only in savannah monkeys, but also in patas monkeys in Kala Maloue. The rates of agonistic interactions during feeding between patas monkeys were equivalent to those between savannah monkeys in Kala Maloue; further, these rates were significantly higher than those of both Laikipia patas and savannah monkeys. The results imply that patas monkeys in Kala Maloue are not egalitarian, but are despotic, similar to savannah monkeys. Disparity in the dominance hierarchies of patas monkeys between Kala Maloue and Laikipia were attributable to the differences in the characteristics of food resources. Although patas monkeys in Laikipia subsist on small and dispersed food resources within a high-density area, those in Kala Maloue subsisted on food resources that were clumped in intermediate-sized patches within a low-density area. This study shows that the socio-ecological model is applicable not only for interspecific comparisons but also for intraspecific comparisons.     

The effect of inter-opponent distance on the occurrence of reconciliation in stumptail (Macaca arctoides) and rhesus macaques (Macaca mulatta)

Several studies have shown that affiliative contact between opponents increases after conflicts in a number of primate species. This study investigated the effect of inter-opponent distance on the occurence of reconciliation in stumptail and rhesus macaques. Both species were represented by multi-male, multi-female groups housed in large outdoor compounds. Ten-minute focal animal observations during post-conflict (PC) and matched control (MC) samples were collected in which affiliative interactions and the inter-opponent distance at the beginning of each sample were recorded. A total of 251 and 561 PC-MC opponent pairs were obtained for stumptail and rhesus macaques, respectively. Inter-opponent distance was smaller in PC than in MC observations for both stumptail and rhesus macaques. Conciliatory tendency varied as a function of the initial PC-MC inter-opponent distance. In particular, the closer opponents were in PC compared to MC periods, the more likely they were to reconcile. When the inter-opponent distance was the same in PC and MC periods the conciliatory tendency of both species was notably reduced. These findings have implications for the estimation of conciliatory tendency and its use in comparative studies.     

Sex Differences in Reconciliation and Post-Conflict Anxiety in Bonnet Macaques

Rates of reconciliation vary widely between different types of opponents, and post‐conflict anxiety has been proposed to mediate individual variation in reconciliation rates. We investigated the form and function of reconciliation in a wild, provisioned group of bonnet macaques (Macaca radiata) with the prediction that sex differences in post‐conflict anxiety would be associated with sex differences in conciliatory tendency. Individuals in the study group had a conciliatory tendency of 29.3%. Victims avoided their former opponents at a higher rate following aggression than during matched‐control samples, and reconciliation decreased the rate of avoidance. Although victims showed a higher rate of anxiety‐related behavior than did aggressors, anxiety‐related behavior was elevated after aggression and reduced following reconciliation in both victims and aggressors. Female–female opponents showed higher rates of anxiety‐related behavior before reconciliation than they did following unreconciled aggression. In contrast, male–male and female–male opponents showed increased anxiety‐related behavior following aggression regardless of the occurrence of reconciliation. Moreover, female–female opponents had a higher conciliatory tendency than did female–male opponents. The elevated post‐conflict anxiety shown by female–female opponents before reconciliation, along with their high conciliatory tendency, suggests that post‐conflict anxiety promotes reconciliation. In sum, the sex differences in post‐conflict behavior found in this study support the hypothesis that variation in post‐conflict anxiety mediates differential rates of reconciliation.     

Life-history parameters of a wild group of West African patas monkeys (Erythrocebus patas patas)

Based on long-term, although intermittent, observations (2 years 4 months of 14 years), we present data on birth seasonality, age at first birth, interbirth intervals, mortality rates, age at first emigration, and population change of a wild population of West African patas monkeys (Etythrocebus patas patas) in northern Cameroon. Birth season was from the end of December until the middle of February, corresponding to the mid-dry season. In spite of large body size, the patas females had the earliest age at first birth (36.5 monthsold) and the shortest interbirth intervals (12 months) compared to the closely related wild forest guenons. Age at first emigration of the males was considered to occur between 2.5 and 4.5 years. The group size of the focal group drastically decreased between 1984 and 1987, and steadily increased until 1994, then decreased again in 1997. The neighboring group also showed a similar trend in group size. The population decreases were likely to be caused by drought over 3 years. Annual crude adult mortality rate was 4% during population increase periods (PIP) between 1987 and 1994. It rose to 22% during all the periods (AP), including drought over 3 years. Despite their smaller body size, the rate of the wild forest guenons (Cercopithecus mitis) (4%) was the same and much lower than those of the patas during PIP and AP, respectively. The annual average juvenile mortality rate was 13% during PIP and it also rose to 37% during AP. That of wild forest guenons (C. ascanius) (10–12%) was a little lower and much lower than those of the patas during PIP and AP, respectively. These findings were consistent with Charnov's theoretical model of mammalian life-history evolution in that patas with high adult and juvenile mortality showed early and frequent reproduction in spite of large body size. Charnov also considered high adult mortality as a selective force and high juvenile mortality as a density-dependent consequence of high fecundity. Our results support the former but not the latter research findings.     

Post-conflict affiliation by chimpanzees with aggressors: other-oriented versus selfish political strategy

Consolation, i.e., post-conflict affiliation directed from bystanders to recent victims of aggression, has recently acquired an important role in the debate about empathy in great apes. Although similar contacts have been also described for aggressors, i.e., appeasement, they have received far less attention and their function and underlying mechanisms remain largely unknown. An exceptionally large database of spontaneous conflict and post-conflict interactions in two outdoor-housed groups of chimpanzees lends support to the notion that affiliation toward aggressors reduces the latter's aggressive tendencies in that further aggression was less frequent after the occurrence of the affiliation. However, bystander affiliation toward aggressors occurred disproportionally between individuals that were socially close (i.e., affiliation partners) which suggest that it did not function to protect the actor itself against redirected aggression. Contrary to consolation behavior, it was provided most often by adult males and directed toward high ranking males, whereas females engaged less often in this behavior both as actors and recipients, suggesting that affiliation with aggressors is unlikely to be a reaction to the distress of others. We propose that bystander affiliation toward aggressors may function to strengthen bonds between valuable partners, probably as part of political strategies. Our findings also suggest that this post-conflict behavior may act as an alternative to reconciliation, i.e., post-conflict affiliation between opponents, in that it is more common when opponents fail to reconcile.