No behavioural response to kin competition in a lekking species

The processes of kin selection and competition may occur simultaneously if limited individual dispersal i.e. population viscosity, is the only cause of the interactions between kin. Therefore, the net indirect benefits of a specific behaviour may largely depend on the existence of mechanisms dampening the fitness costs of competing with kin. In lekking species, males may increase the mating success of their close relatives (and hence gain indirect fitness benefits) because female prefer large leks. At the same time, kin selection may also lead to the evolution of mechanisms that dampen the costs of kin competition. As this mechanism has largely been ignored to date, we used detailed behavioural and genetic data collected in the black grouse Lyrurus tetrix to test whether males mitigate the costs of kin competition through the modulation of their fighting behaviours according to kinship and the avoidance of close relatives when establishing a lek territory. We found that neighbouring males’ fighting behaviour was unrelated to kinship and males did not avoid settling down with close relatives on leks. As males’ current and future mating success are strongly related to their behaviour on the lek (including fighting behaviour and territory position), the costs of kin competition may be negligible relative to the direct benefits of successful male-male contests. As we previously showed that the indirect fitness benefits of group membership were very limited in this black grouse population, these behavioural data support the idea that direct fitness benefits gained by successful male-male encounters likely outbalance any indirect fitness benefits

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

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

Post-conflict affiliation as conflict management in captive bottlenose dolphins (Tursiops truncatus)

Post-conflict affiliation between former opponents or between one of the former opponents and bystanders might have the function of conflict management, which reduces the costs associated with aggressions. One of the suggested functions of post-conflict affiliation is decreased renewed aggressions directed from aggressors to victims. However, the effect of post-conflict affiliation on renewed aggressions by victims has not been investigated. We examined whether post-conflict affiliations decreased the number of renewed aggressions initiated by winners or losers in captive bottlenose dolphins. Both winners and losers initiated renewed aggressions. However, these aggressions decreased after post-conflict affiliation between former opponents, initiated by bystanders to winners, initiated by losers to bystanders, and initiated by bystanders to losers. Post-conflict affiliation between former opponents is suggested to function as reconciliation. Post-conflict affiliation initiated by losers to bystanders is suggested to function as the protection of losers. Post-conflict affiliations initiated by bystanders to one of former opponents are suggested to function as both appeasement and protection of the opponent who affiliates with bystanders

The importance of the altricial – precocial spectrum for social complexity in mammals and birds:A review

Various types of long-term stable relationships that individuals uphold, including cooperation and competition between group members, define social complexity in vertebrates. Numerous life history, physiological and cognitive traits have been shown to affect, or to be affected by, such social relationships. As such, differences in developmental modes, i.e. the ‘altricial-precocial’ spectrum, may play an important role in understanding the interspecific variation in occurrence of social interactions, but to what extent this is the case is unclear because the role of the developmental mode has not been studied directly in across-species studies of sociality. In other words, although there are studies on the effects of developmental mode on brain size, on the effects of brain size on cognition, and on the effects of cognition on social complexity, there are no studies directly investigating the link between developmental mode and social complexity. This is surprising because developmental differences play a significant role in the evolution of, for example, brain size, which is in turn considered an essential building block with respect to social complexity. Here, we compiled an overview of studies on various aspects of the complexity of social systems in altricial and precocial mammals and birds. Although systematic studies are scarce and do not allow for a quantitative comparison, we show that several forms of social relationships and cognitive abilities occur in species along the entire developmental spectrum. Based on the existing evidence it seems that differences in developmental modes play a minor role in whether or not individuals or species are able to meet the cognitive capabilities and requirements for maintaining complex social relationships. Given the scarcity of comparative studies and potential subtle differences, however, we suggest that future studies should consider developmental differences to determine whether our finding is general or whether some of the vast variation in social complexity across species can be explained by developmental mode. This would allow a more detailed assessment of the relative importance of developmental mode in the evolution of vertebrate social systems

Peace-Making in Marsupials: The First Study in the Red-Necked Wallaby (Macropus rufogriseus)

The issue of reconciliation has been widely investigated in many eutherian mammal species. Nevertheless, no data are available for marsupial mammals. Indeed, the majority of reports focus on group dynamics from an ecological and reproductive perspective, but no study has investigated them from a social point of view. We observed the red-necked wallaby colony (Macropus rufogriseus) hosted at the Tierparc Zoo Berlin (Germany) and collected data on aggressive and post-conflict interactions between group members. We found that the phenomenon of reconciliation is present in the study species (mean group CCT 27.40% ±8.89% SE). Therefore, we demonstrated, for the first time, the occurrence of reconciliation in a gregarious marsupial mammal. Post-conflict reunion was not affected by the relationship quality between individuals (friendship or kinship) but it was fine-tuned according to the aggression intensity. For example, low intensity conflicts were reconciled whereas high intensity ones were not. Reconciliation reduced anxiety-related scratching in both of the former opponents and limited further attacks towards the victim during the post-conflict period. These findings suggest that the red-necked wallaby, like many eutherian species, can evaluate the costs of reconciliation and engage in peace-making behavior in the right contexts, in order to maximize its pay-offs

Group hunting within the Carnivora: physiological, cognitive and environmental influences on strategy and cooperation

Cooperative hunting is believed to have important implications for the evolution of sociality and advanced cognitive abilities. Variation in the level of hunt organisation amongst species and how their cognitive, behavioural and athletic adaptations may contribute to observed patterns of cooperative hunting behaviour, however, are poorly understood. We, therefore, reviewed the literature for evidence of different levels of hunt organisation and cooperation in carnivorans and examined their social and physical adaptations for hunting. Descriptions of group hunting were scarce for many species and often of insufficient detail for us to be able to classify the level of hunt organisation involved. However, despite this, reports of behaviour fitting the description of collaboration, the most advanced level of hunt organisation, were found in over half the carnivorans reported to hunt cooperatively. There was no evidence that this behaviour would require advanced cognitive abilities. However, there was some evidence that both social mechanisms reducing aggression between group members and information transfer amongst individuals may aid cooperative hunting. In general, the cooperative strategies used seemed to depend partly on the species' locomotor abilities and habitat. There was some evidence that individuals take on consistent roles during cooperative hunts in some species, but it was not clear if this reflects individuals' physical differences, social factors or life experiences. Better understanding of the social, cognitive and physical mechanisms underlying cooperative hunting, and indeed establishing to what degree it exists in the first instance, will require more data for multiple individuals and species over many hunts.</p