Social tension after grooming in wild Japanese macaques (Macaca fuscata yakui) is sex specific and sensitive to social relationships.

Changes in the rate of self-directed behavior-a proxy for social tension-offer valuable insights into individuals' experiences of social interactions. Many studies have tested the tension-reduction hypothesis, whereby grooming is expected to reduce social tension in the grooming partners. However, it is still unclear whether responses to grooming are affected by social factors such as an individual's role or social relationship with their partner, and whether responses are similar for females and males.

Emotional states following grooming in female mandrills.

Grooming is a common cooperative behavior whose exact costs and benefits are still to be fully elucidated. In this study, we evaluated the emotional consequences of giving and receiving grooming in mandrills (Mandrillus sphinx), and how these may change along time after the termination of grooming. We used scratching as a behavioral indicator of anxiety-like emotions.

Precursors and aftermath of severe targeted aggression in captive cotton-top tamarins.

We observed a zoo-housed group of cotton-top tamarins (Saguinus oedipus) before and after a bout of severe targeted aggression directed towards two of its members. The aggression was so severe and repeated that the zoo personnel was forced to remove the two victims and the main aggressor. In the tense period that preceded removal, the tamarins showed increased aggression, a steeper and linear dominance hierarchy, and reduced post-conflict reconciliation compared to the period following removal.

Variation in communicative complexity in relation to social structure and organization in non-human primates.

Communicative complexity relates to social complexity, as individuals in more complex social systems either use more signals or more complex signals than individuals living in less complex ones. Taking the individual group member's perspective, here we examine communicative complexity in relation to social complexity, which arises from two components of social systems: social structure and social organization. We review the concepts of social relationships and social complexity and evaluate their implications for communicative and cognitive complexity using examples from primate species.

Anxiety in Geoffroy's spider monkeys (Ateles geoffroyi): Can scratching be used as an indicator?

Self-directed behavior, such as self-scratching (hereafter, scratching), occurs in several taxa across the animal kingdom, including nonhuman primates. There is substantial evidence that scratching is an indicator of anxiety-like emotions in a variety of nonhuman primate species. Despite its importance as a window into emotional states, few studies have investigated scratching in Platyrrhines.

Testing the two sides of indirect reciprocity in tufted capuchin monkeys.

We addressed two different aspects of indirect reciprocity in tufted capuchin monkeys (Sapajus spp.) studying two common cooperative behaviours, grooming and food sharing. In an observational study, we tested whether capuchin monkeys were more likely to groom an individual that had just groomed a group mate than an individual that had not groomed anybody.

Conflict over grooming topography between mandrill groomers and groomees.

Grooming directed to different body areas is likely to imply different costs and benefits for groomers and groomees. In this study, we investigated social influences on grooming topography in captive female mandrills (Mandrillus sphinx). Subordinate groomers preferred to direct grooming to "safe" areas (the back and rump) compared to dominant groomers, while subordinate groomees did not solicit preferentially grooming to safe areas.

Monitoring of group mates in relation to their behavior in mandrills.

Primates are known to have considerable knowledge about the social relationships that link their group mates and are likely to derive this information from observing the social interactions that occur in their social group. They may, therefore, be hypothesized to pay particular attention to the social interactions involving group mates. In this study, we evaluated how the attention captive mandrills (Mandrillus sphinx) devote to their group mates was modulated by the behavior of the latter.

Mandrills represent their own dominance hierarchy on a cardinal, not ordinal, scale.

Attempts to measure dominance relationships using cardinal, rather than ordinal ranks have a long history. Nevertheless, it is still unclear if cardinal dominance ranks have an impact on the life of animals. In particular, no information is available on how individual group living animals represent their own dominance hierarchy.

Age-related changes in the social behavior of tufted capuchin monkeys.

The effects of aging on the social behavior of nonhuman primates is little understood, especially in New World monkeys. We studied the members of a colony of tufted capuchin monkeys (Sapajus sp.) in order to evaluate age related changes in their social behavior.

Acquisition and functional consequences of social knowledge in macaques.

To manoeuvre in complex societies, it is beneficial to acquire knowledge about the social relationships existing among group mates, so as to better predict their behaviour. Although such knowledge has been firmly established in a variety of animal taxa, how animals acquire such knowledge, as well as its functional significance, remains poorly understood. In order to understand how primates acquire and use their social knowledge, we studied kin-biased redirected aggression in Japanese macaques () relying on a large database of over 15 000 aggressive episodes.

Factors affecting cashew processing by wild bearded capuchin monkeys (Sapajus libidinosus, Kerr 1792).

Cashew nuts are very nutritious but so well defended by caustic chemicals that very few species eat them. We investigated how wild bearded capuchin monkeys (Sapajus libidinosus) living at Fazenda Boa Vista (FBV; Piauí, Brazil) process cashew nuts (Anacardium spp.) to avoid the caustic chemicals contained in the seed mesocarp.

Symmetry-based reciprocity: evolutionary constraints on a proximate mechanism.

Background. While the evolution of reciprocal cooperation has attracted an enormous attention, the proximate mechanisms underlying the ability of animals to cooperate reciprocally are comparatively neglected. Symmetry-based reciprocity is a hypothetical proximate mechanism that has been suggested to be widespread among cognitively unsophisticated animals.

Reciprocity in group-living animals: partner control versus partner choice.

Reciprocity is probably the most debated of the evolutionary explanations for cooperation. Part of the confusion surrounding this debate stems from a failure to note that two different processes can result in reciprocity: partner control and partner choice. We suggest that the common observation that group-living animals direct their cooperative behaviours preferentially to those individuals from which they receive most cooperation is to be interpreted as the result of the sum of the two separate processes of partner control and partner choice.

Short-term costs and benefits of grooming in Japanese macaques.

This study investigated the short-term consequences of giving grooming in Japanese macaques (Macaca fuscata) in order to obtain information on its immediate costs and benefits. Giving grooming was associated with increased aggression received from groomees and decreased aggression received from third parties (but only as long as the groomer maintained proximity to the groomee). Grooming was also associated with decreased scratching rates.

Exchanging grooming, but not tolerance and aggression in common marmosets (Callithrix jacchus).

In this study, we investigated the reciprocal exchanges of grooming, tolerance and reduced aggression in common marmosets (Callithrix jacchus), a cooperatively breeding primate whose groups are typically characterized by uniformly high genetic relatedness and high interdependency between group members. Both partner control and partner choice processes played a role in the reciprocal exchanges of grooming. In contrast, we did not find any evidence of reciprocity between grooming and tolerance over a preferred food source or between grooming and reduced aggression.

Do displacement activities help preschool children to inhibit a forbidden action?

Displacement activities are commonly recognized as behavioral patterns, mostly including self-directed actions (e.g., scratching, self-touching), that often occur in situations involving conflicting motivational tendencies.

Partner choice promotes cooperation: the two faces of testing with agent-based models.

Reciprocity is one of the most debated among the mechanisms that have been proposed to explain the evolution of cooperation. While a distinction can be made between two general processes that can underlie reciprocation (within-pair temporal relations between cooperative events, and partner choice based on benefits received), theoretical modelling has concentrated on the former, while the latter has been often neglected. We developed a set of agent-based models in which agents adopted a strategy of obligate cooperation and partner choice based on benefits received.

Food transfers in capuchin monkeys: an experiment on partner choice.

Although most primates live in groups, experiments on reciprocity usually test individuals in dyads. This could hide the processes emerging in richer social settings, reducing the ecological validity of the results. We run an experiment on reciprocal food transfers testing capuchin monkeys (Cebus apella) in triads, so that subjects could choose to allow access to their food to either of their two partners.

Self-protective function of post-conflict bystander affiliation in mandrills.

Background: Affiliative interactions exchanged between victims of aggression and individuals not involved in the original aggression (bystanders) have been observed in various species. Three hypothetical functions have been proposed for these interactions: consolation, self-protection and substitute reconciliation, but data to test them are scanty.

Methodology/principal Findings: We conducted post-conflict and matched control observations on a captive group of mandrills (Mandrillus sphinx).

Hierarchical steepness, counter-aggression, and macaque social style scale.

Nonhuman primates show remarkable variation in several aspects of social structure. One way to characterize this variation in the genus Macaca is through the concept of social style, which is based on the observation that several social traits appear to covary with one another in a linear or at least continuous manner. In practice, macaques are more simply characterized as fitting a four-grade scale in which species range from extremely despotic (grade 1) to extremely tolerant (grade 4).

Grooming up the hierarchy: the exchange of grooming and rank-related benefits in a new world primate.

Seyfarth's model assumes that female primates derive rank-related benefits from higher-ranking females in exchange for grooming. As a consequence, the model predicts females prefer high-ranking females as grooming partners and compete for the opportunity to groom them. Therefore, allogrooming is expected to be directed up the dominance hierarchy and to occur more often between females with adjacent ranks.