mystery of yawning
Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal
Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal

mise à jour du
28 novembre 2010
Aggression does not increase friendly contacts among bystanders in geladas (Theropithecus gelada)
Alessia Leone, Michele Mignini, Giada Mancini, Elisabetta Palagi
Centro Interdipartimentale Museo di Storia Naturale e del Territorio
Natural History Museum, University of Pisa, Italy
Displacement activities


Aggression within a social group may affect bystanders' affinitive behaviour with other bystanders. After a conflict such affiliations, termed 'quadratic', may serve to reduce tension. This particular kind of conflict management has been found in hamadryas baboons. Following the classical and well-established approach for studying post-conflict behaviour [post-conflict/matched control method (PC/MC)], we collected behavioural data on a group of geladas (Theropithecus gelada) in order to check for the presence of quadratic affiliations. A total of 192 PC/MC pairs were collected on both adults and immature individuals. We did not find any increase of affiliation levels between bystanders during PC compared with MC condition. The distribution of affinitive quadratic interactions was not affected by either kinship or relationship quality of bystanders. Moreover, comparison of yawning and self-scratching behaviours (two of the typical non-primate displacement activities under stressful situations) recorded during PCs and MCs did not show any variation in the two conditions. Probably, due to the male tolerance and social cohesiveness in geladas, witnessing a fight does not necessarily induce a sufficient increase of tension in bystanders to be reduced by quadratic affiliation.
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-Leone A, Mignini M, Mancini G, Palagi E. Aggression does not increase friendly contacts among bystanders in geladas (Theropithecus gelada) Primates. 2010;51(4):299-305
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Social animals possess behavioural tools to settle conflicts and offset the costs of competition within a group (Aureli et al. 2002). Specifically, to cope with the conflict aftermath and social damage caused by aggressions, groupliving species use a variety of peace-keeping tactics (Aureli et al. 2002; Silk 2007). Such peaceful mechanisms include reconciliation (post-conflict reunion of former opponents) and triadic contacts (affinitive patterns directed by bystanders towards one of the former opponents and vice versa) (de Waal and van Roosmalen 1979; Palagi et al. 2004, 2006, 2008a, b; Cordoni et al. 2006; Koski and Sterck 2007, Palagi and Cordoni 2009; Leone and Palagi 2010). However, a further post-conflict mechanism has been ascertained in non-human primates. Bystanders can increase their affiliation levels after witnessing an aggressive act between other group members, especially kin (chimpanzees, de Waal 1982; vervet monkeys, Cheney and Seyfarth 1989; hamadryas baboons, Judge and Mullen 2005). Such 'quadratic' post-conflict affiliation might reduce social tension generated by the previous aggression.
Here, we aimed to verify the occurrence of quadratic post-conflict affiliation in geladas (Theropithecus gelada). Geladas live in multi-level societies in which the basic level consists of one-male units (OMU5) (Kawai 1979; Mori 1979; Kawai et al. 1983; Dunbar 1984). The species is characterized by male dispersal and female philopatry, with social relationships which centre primarily round the females (Dunbar and Dunbar 1975; Mancini and Palagi 2009). Most of the male's friendly interactions are with adult females, even though the adult male shows a preference for a few of them (Dunbar 1983). Different from hamadryas baboons, which maintain group integrity by aggressive herding by the males, the social cohesion of the gelada unit is the result of strong bonds among companions (Bramblett 1970). The relationships are determined primarily by the use of protected threats and coalitions (Leone and Palagi 2010), and there is a preference for social partners, also among the females (Mon et al. 2003; Palagi et al. 2009). In geladas, reconciliation has recently been found and quantified (Leone and Palagi 2010). Moreover, Leone and Palagi (2010) found that valuable relationships were predictive of high levels of conciliatory contacts. In this view, geladas are a good model species to examine all possible mechanisms at the basis of natural conflict resolution. Therefore, we focussed our attention on quadratic post-conflict affiliation and on some potential factors (kinship and relationship quality) that could affect this kind of conflict management.
Intra-group aggression may have consequences for the relationship not only between opponents but also between bystanders (de Waal 1982). For example, several studies indicated that the relatives of two animals involved in a fight were generally more likely to affiliate in the minutes following the aggression (Cheney and Seyfarth 1989; Judge and Mullen 2005). After witnessing a fight, both adult and immature geladas did not search for affinitive contact with other group members. Moreover, post-conflict affiliation was not positively affected by either kinship or friendship of the two bystanders.
In primates, self-directed behaviours (SDB) or displacement activities are good indicators of anxiety (Maestripieri et al. 1992; Kutsukake and Castles 2001). In geladas, bystanders' displacement activities were not significantly higher during post-conflict intervals (PCs) compared with baseline intervals (MCs) (Fig. 3). Apparently, witnessing aggression did not seem to increase tension or anxiety in the observer. This could explain why bystanders did not approach and affiliate each other in post-conflict (PCs) more than in control condition (MCs). L Probably, most of the intra-group aggressions did not L have an aftermath at group level since conflict escalation is rare (Leone and Palagi 2010). However, it seems that some animals adopt an alternative tactic. Those subjects sharing weak relationships tended to keep away from each other (dispersed pairs were more frequent than attracted pairs) after witnessing a fight. Even though the result has to be taken with caution (due to the possibility
of a type I error), this finding seems to suggest that quadratic affiliation implied a certain amount of risk for the interactants, which resulted in a conflict-avoidance strategy. In hamadryas baboons, quadratic affiliation mechanism was present and occurred mainly between preferred nonkin partners rather than kin. The analysis of SDB in this species revealed that the presence of intra-group aggression caused a stressful emotional state in the observers (Judge and Mullen 2005). Why are there so strikingly different results in two species (Theropithecus gelada and Papio hamadryas) showing similar social structures (one-male unit)?
Judge and Mullen (2005) interpreted their findings in the light of male despotic presence (Kummer 1968; Gore 1994). In fact, the male leader was perceived as a powerful threat by group members even though he was not directly involved in the previous conflict. Romero and Castellanos (2010) underlined the importance of hamadryas male agonistic ability (expressed in dominance indexes) in the process of female acquisition and group control. In this view, after a fight, hamadryas bystanders were probably highly motivated to reduce arousal and social tension. To reduce post-conflict stress, hamadryas engaged in affiliation with non-kin partners. The authors emphasized the tension-reduction function of quadratic affinitive interactions; if overall tension was successfully reduced in the group, then the response might have some generalized influence on aggressive potential (Judge and Mullen 2005).
Notwithstanding the similarity with hamadryas social organization, geladas show some peculiarities in the nature of their social dynamics. In contrast to geladas (Mancini and Palagi 2009), in hamadryas Colmenares (2004) found that grooming was more frequent in female-male than in female-female dyads and, more recently, Romero et al. (2008) showed that the highest rate of reconciliation occurred between leader males and their females. The absence of any sex-trend bias in gelada reconciliation can be interpreted in light of the female social network that characterizes the species (Leone and Palagi 2010). The relationships within the typical gelada one-male unit revolve around females (Palagi et al. 2009), who form the core of the cohesion and stability typical of OMUs. Different from hamadryas, the strength of gelada female bonds suffices to maintain OMU integrity despite the absence of the male (Dunbar and Dunbar 1975; Moth et al. 2003). In this view, the female social network characteristic of this species weakens the power of the male, thus contributing to a less despotic social environment. Probably, this more relaxed social setting contributes to limit post-conflict anxiety experienced by bystanders.

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Aggression does not increase friendly contacts among bystanders in geladas (Theropithecus gelada) Leone A, Mignini M, Mancini G, Palagi E. Primates. 2010;51(4):299-305.