Social Contact Following Severe Aggression in Rhesus Macaques (Macaca mulatta): A New Test of the Consolation Hypothesis

Previous studies on macaque species revealed no evidence of consolation: affiliative contact between the loser of an aggressive interaction and a third party. However, typically, the researchers used short observation periods and latency to make first affiliative contact as a dependent measure. Based on social stress buffering literature, I predicted that by employing longer observation periods and percentage of time in affiliative contact as a dependent measure, I would be more likely to detect increases in affiliative contact following aggression. I observed adult female rhesus macaques for 1 hr after they received severe aggression and for 1 hr after some affiliative contact, and measured time spent in affiliative contact using instantaneous recording at 30-sec intervals. Contrary to prediction, victims of attack did not spend a greater percentage of time in affiliative contact postaggression as compared to postaffiliation. Subjects were also less likely to initiate contact with other individuals and were more likely to have contact with individuals that were dominant to their aggressor, following aggression. These results provide converging evidence that affiliative contact is not increased following aggression in macaques. I discuss the failure to bear out the predictions based on the social stress buffering literature in terms of rhesus social dynamics, the nature of aggression as a stressor, and possible mechanisms for the social stress buffering effect.     

Postconflict Behavior of Captive Brown Capuchins in the Presence and Absence of Attractive Food

Most of what we know about postconflict behavior comes from studies on chimpanzees and other Old World semiarboreal and semiterrestrial species. Few studies have investigated whether the context of a fight affects reconciliation—selective postconflict attraction between former opponents—and consolation: selective attraction between conflict participants and other group members. We studied social conflict and its aftermath in two captive groups of brown capuchins (Cebus apella), an arboreal New World species. We observed postconflict behavior in two contexts: (1) during the presence of highly attractive, clumped food—food condition—and (2) in the absence of such food—nonfood condition. Commercial monkey chow was available ad libitum in the nonfood condition. A comparison of postconflict and control observations revealed a conciliatory tendency in the capuchins, but only following fights that occurred in the absence of highly attractive food. Other group members tended not to seek postconflict contact with former conflict participants. However, when shortly after fights recipients of aggression, but not aggressors, initiated affiliation with third parties, the latter not only allowed proximity or contact but also often reciprocated through grooming, play, and especially the exchange of friendly signals. We discuss these results within the framework of current knowledge of postconflict behavior with special emphasis on similarities and differences in the postconflict behavior of Cebus and Pan.     

Reconciliation and Consolation in Captive Western Gorillas

We studied post-aggression mechanisms in a captive group of western gorillas (Apenheul Primate Park, The Netherlands) and compared them with those of wild mountain gorillas (Gorilla beringei). We found the same trend for reconciliation that wild mountain gorillas show: reconciliation occurred only between adult male-female dyads, while it was absent in the other sex-age class combination. There were both solicited and nonsolicited contacts; the latter finding is in contrast with the result obtained in wild mountain gorillas, in which consolation was absent. Immature females were more likely to offer consolation toward both related and unrelated individuals. Consolation did not reduce the likelihood of further attacks among group members. It may be that, as the α-male plays a fundamental role in preventing the spread of conflicts throughout the entire group, triadic contacts become ineffective for the function. The levels of consolation were higher in absence of reconciliation than in its presence, suggesting that consolation may function as an alternative mechanism in stress reduction of the victim.     

On operationally defining reconciliation

Post-conflict reconciliatory behavior has been reported to occur with variable frequencies in different primate groups and species. Because different investigators have used different criteria to operationalize reconciliation, however, it is possible that the variation reported merely reflects different methods of study. To compare different groups and species in a meaningful way, an accurate operationalization of reconciliation is necessary. This study explores the correlation between operationally defined reconciliation (what observers recognize, such as friendly reunion) and functional reconciliation (behavior that restores a dyadic social relationship) in a group of captive long-tailed macaques, using results from an experiment originally undertaken to demonstrate the function of friendly reunions in restoring dyadic tolerance after aggression. In dyads of unrelated animals, reunions were equally effective in restoring tolerance whether they involved body contact, overt friendly gestures, or mere proximity. Classification of post-conflict reunions as “reconciliations” depends on comparisons with control observations; these comparisons have been carried out in several ways. Comparisons using the “n-minute rule” missed functional reconciliations, whereas those based on the “post-conflict/matched-control rule” appeared to lead to more accurate classification of functional reconciliations. Post-conflict reunions were equally effective in restoring tolerance whether they were initiated by the original aggressor or by the victim. An accurate operational definition of reconciliation, not a conservative one, is prerequisite to comparisons of the frequency of this behavior, and depends on empirical verification. This study suggests specific guidelines for an operational definition based on such verification. © 1993 Wiley-Liss, Inc.     

Dyadic and triadic reconciliation in pigtail macaques (Macaca nemestrina)

The tendency in primates for former antagonists to approach and affiliate following aggression has been termed reconciliation because the response is thought to resolve social conflicts produced by aggression. In primate societies, however, an aggressive interaction between two individuals often spreads to include other group members, especially the kin of the combatants. If post conflict affiliation resolves aggressive conflicts in a group, then affiliative increases might occur between combatants and the kin of their opponents following aggression as well as between former opponents. This hypothesis was tested in a captive group of 39 pigtail macaques (Macaca nemestrina) by comparing affiliative response frequencies of combatants during the 5 minute period following aggression to affiliative response frequencies during 5 minute baseline periods not preceded by aggressive activity. Following aggression, affiliation rates increased between combatants and their opponents, aggressors and the kin of their opponents, and aggressors and their own kin. Additional analyses showed that aggression among kin was reconciled more often than aggression among nonkin. Recipients of aggression reconciled with their attackers more often than aggressors reconciled with their victims. Animals with similar dominance ranks reconciled proportionately more often than those with large rank disparities and aggressive infractions of a calculated dominance hierarchy were reconciled more often than attacks consistent with the hierarchy. Results suggest that both dyadic and triadic reconciliations occur in M. nemestrina and that compared to other primate species M. nemestrina exhibit a moderate-to-high conciliatory tendency.     

Duration and outcome of intergroup conflict influences intragroup affiliative behaviour

Theoreticians have long suggested that the amount of intergroup conflict in which a group is involved could influence the level of cooperation or affiliation displayed by its members. Despite the prevalence of intergroup conflicts in many social animal species, however, few empirical studies have investigated this potential link. Here, I show that intragroup allopreening rates are highest in green woodhoopoe (Phoeniculus purpureus) groups that have the greatest involvement in intergroup conflict. One reason for this relationship is a post-conflict increase in allopreening, and I demonstrate for the first time that both conflict duration and outcome influence subsequent allopreening rates: group members allopreened more following long conflicts and those they lost compared with short conflicts and those they won, perhaps because the former are more stressful. The increase in affiliative behaviour was the result of more allopreening of subordinate helpers by the dominant breeding pair, which may be because the breeders are trying to encourage helpers to participate in future conflicts; relative group size influences conflict outcome and helpers contribute more to conflicts than do the breeding pair. These results emphasize that our understanding of cooperation and group dynamics can be enhanced by investigations of how intergroup interactions affect intragroup processes.     

Aggression and Reconciliation in Two Captive Groups of <Emphasis Type="Italic">Lemur catta</Emphasis>

Kappeler excluded the presence of reconciliation in a free-ranging group of Lemur catta, but a recent study on the same group indicated reconciliation, though with a very long PC duration. We collected data on 2 captive groups of ring-tailed lemurs at the Pistoia Zoo (Italy) in order to shed light on conflict resolution in the species. We investigated the influence of seasonality and of a targeted aggression episode on the occurrence of reconciliation. We collected 164 PC-MC pairs for the A group and 141 for the B group. We performed all analyses at the dyadic level via randomization procedures. Despite the targeting episode, we found no difference in the levels of aggression between the 2 groups. In contrast, just before the onset of the targeting episode, B showed significantly lower rates of affinitive behaviors versus A. Reconciliation occurred in A, whereas it was absent in B. Therefore, we suggest that in B, with the decrease of baseline affinitive interactions associated with the beginning of the targeting episode, the function of postconflict reunions probably stopped working. On the whole, we found that contrasting results were probably related to different seasonal and social conditions (A: breeding/pregnancy season, characterized by higher tolerance rates; B: birth season, characterized by lower tolerance rates). Accordingly, reconciliation should be monitored throughout the different seasonal phases.     

Differences in Subadult Behaviors of Chimpanzees Living in Peer Groups and in a Family Group

In several primate species, peer-group rearing conditions affect the development of social behavior. We compared the social behavior of adolescent chimpanzees reared in peer groups and in a family group to see whether chimpanzees raised under different regimes show differences in sexual behavior, teasing behavior, and grooming behavior and in their ability to cope with support strategies. Surprisingly, the lack of opportunity to practice or to watch in peer groups had no measurable effect on the development of normal sexual behavior in adolescence and adulthood. Peer-group individuals groomed each other as much as peers did in the zoo. Sex differentiation in reaction to teasing and in conflict initiatives may indicate only an earlier sex differentiation in the zoo than in the peer group. This result may be attributed to the difference in demographic composition of the groups instead of some inherent difference in skill. Peer-group chimpanzees simply cannot find adult partners with which they may preferably test their position. However, there was a lack of sex differentiation in the reaction to teasing and in the number of conflicts started; both are indications of lesser sex-role development in the peer-group adolescents. Furthermore, the frequency of giving support to peers in conflicts differed, which suggests a greater ability in zoo adolescents to cope with support strategies. Accordingly, providing more natural conditions than is usual in laboratories may still add considerably to chimpanzee well-being.     

Relation between the dominance rank of female rhesus monkeys and their access to males

Systematic observations were made on 12 measures of the sexual, aggressive, and social interactions of 24 male–female pairs of rhesus monkeys in six social groups, each consisting of one male and four ovariectomized females tested in a large room. Each female in a group was treated in turn first with estradiol alone and then with estradiol and progesterone in combination. When hormone-treated, the female was also observed during pair tests with the male in the same large observation room (four males, eight females, 240 group tests, 240 pair tests). The dominance ranks of females during group tests were determined post hoc by means of the dominance index [Zumpe & Michael, American Journal of Primatology 10:291–300, 1986]. In all six groups, the most dominant female virtually monopolized the male, and the subordinate females' interactions with the male, assessed during pair tests, were almost completely suppressed during group tests. This “dominant female effect” was a robust phenomenon that depended solely on female dominance rank. It was independent of the identity and hormonal status of females and of the social preferences of males as expressed in pair tests. These findings demonstrate the existence of female mate competition in an Old World primate.     

Acute changes in social composition and agonistic behavior in male vervet monkeys (Cercopithecus aethiops sabaeus)

Among nonhuman primates the composition of social groups influences the interactions of group members. We assessed the effects of acute changes in social composition on behavior among 15 adult male vervet monkeys (Cercopithecus aethiops sabaeus). Subjects were observed in their basal social groups which comprised 3 adult males, 2–4 adult females, and offspring; and in two subgroups consisting of either two or three adult males. Agonism and vigilance increased in smaller groups relative to basal conditions, while subjects in two-male groups displayed more aggression than those in three-male groups. These findings suggest that, among male vervet monkeys, acute disruption of stable social groups increases aggressive behavior, and that the amount of agonism is influenced by the composition of the consequent subgroups. © 1992 Wiley-Liss, Inc.     

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.     

Within-group aggression and the value of group members: theory and a field test with social wasps

We present a simple, general model of how the optimal levelof intra-group aggression should vary in different social contexts.A key component of this model is the value of the recipientof aggression to a potential aggressor (i.e., the ratio of expectedlong-term group productivity with the recipient present to theexpected group productivity with the recipient absent). Therecipient's value measures its contribution to group reproductivesuccess. We demonstrate theoretically that if aggression increasesthe aggressor's share of the group's expected total reproductiveoutput, but at the same time decreases the magnitude of thisoverall reproductive output, then the optimal level of aggressiontoward a recipient will decrease with increasing recipient'svalue. This proof establishes a rigorous theoretical connectionbetween the level of aggression within a group and the benefitsof belonging to such a group and can be tested by experimentallymanipulating the values of group members to each other. We test,and thus illustrate the utility of, this model by examiningaggression within experimentally-manipulated foundress associationsof social wasps. We show that the value of co-foundresses toeach other in the social wasp Polistes fuscatus lies in theirability to provide insurance against colony failure caused bythe loss of all tending foundresses. Removals of worker-destinedeggs and pupae, which increase the value of co-foundresses,both lead to significant reductions in aggression by the dominantfoundress, despite the fact that the immediate, selfish benefitsof competitive aggression should increase when empty brood cellsare present Removal of reproductive-destined eggs, which doesnot affect co-foundress value, but increases the benefits ofselfish aggression, causes a significant increase in aggressionby beta foundresses. Finally, wing reduction of subordinateco-foundresses significantly increases aggression by dominantfoundresses, as expected since the subordinate's value is reduced.Our results indicate that foundress aggression is sensitiveto the value of future cooperation, as predicted by the optimalaggression model. The model may apply widely to both invertebrateand vertebrate societies