Abstract: Matrilineal dominance systems, which characterize several species of cercopithecines, are determined largely by the patterning of third-party aggressive interventions in conflicts. Although the role of interventions in structuring rank relations has received much attention, very few studies have dealt specifically with the development of intervention behavior. In other words,most studies have focused on the interventions received and their effect on the recipients rather than on the interventions performed and the goals of the interveners. We analyzed the intervention behavior of 10 juvenile females in a colony of 40 Japanese macaques (Macaca fuscata)housed at the University of Montreal Laboratory of Behavioral Primatology. The analysis of 749 interventions performed by the juveniles over their first 4 years and 2425 interventions received over the same period reveals that (1) juvenile females intervened selectively against females ranking below their mother, (2) they began to intervene at about the same time that they began to challenge the latter females in dyadic contests, (3) they sided with females as well as with males against these females, (4) juvenile interveners incurred little risks in terms of aggressive retaliation from their targets, (5) they derived immediate benefits in terms of conflicts won over stronger targets, (6) interventions often did not take place when the possible recipients needed support, and (7) interveners did not conform to a pattern of mutually preferential support. These results support the view that interventions by juveniles are selfish (vs altruistic) and constitute a low-cost and effective means to target and to outrank prospectively subordinate females.

Abstract: The aim of this study was to see if behavioral lateralization in hand use benefits a lateralized organism in nature. We recorded wild chimpanzees (Pan troglodytes schweinfurthii) at Gombe, Tanzania, fishing for termites (Macrotermes spp.), an extractive foraging task using elementary technology. We compared individual apes who were completely lateralized, using only one hand or the other for the task, versus those who were incompletely lateralized, using either hand. Exclusively lateralized individuals were more efficient, that is, gathered more prey per unit effort, but were no different in success or error rate from incompletely lateralized apes. This is the first demonstration of a payoff to laterality of behavioral function in primates in conditions of ecological validity.

Abstract: Place learning abilities represent adaptations that contribute also to foraging efficiency under given spatio-temporal conditions. We investigated if this ability in turn constrains decision making in two sympatric vole species: while the herbivorous common vole (Microtus arvalis) feeds on spatio-temporally predictable food resources (e.g. roots, tubers and shoots of plant tubers), the omnivorous bank vole (Myodes glareolus) additionally subsists on temporally unpredictable food resources (e.g. insects and seeds). Here, we compare the spatial reference memory and working memory of the two species. In an automated operant home cage with eight water places, female voles either had to learn the fixed position of non-depletable places (reference memory task) or learn and avoid previously visited water places depleted in a single visit (win-shift task). In the reference memory task, Microtus females required significantly more choices to find all water places, initially performed slightly worse than Myodes females, and displayed slightly lower asymptotic performance. Both species were highly similar in new learning of the same task. In the more complex win-shift task, asymptotic performance was significantly lower in Microtus (72% correct) than in Myodes (79%). Our results suggest that both vole species resemble each other in their efficiency to exploit habitats with low spatio-temporal complexity but may differ in their efficiency at exploiting habitats with temporally changing spatial food distributions. The results imply that spatial ability adjusted to specific food distributions may impair flexible use of habitats that differ in their food distribution and therefore, decrease a species’ chances of survival in highly dynamic environments.

Abstract: Great ape gesture has become a research topic of intense interest, because its intentionality and flexibility suggest strong parallels to human communication. Yet the fundamental question of whether an animal species’ gestures carry specific meanings has hardly been addressed. We set out a systematic approach to studying intentional meaning in the gestural communication of non-humans and apply it to a sample of orangutan gestures. We propose that analysis of meaning should be limited to gestures for which (1) there is strong evidence for intentional production and (2) the recipient’s final reaction matches the presumed goal of the signaller, as determined independently. This produces a set of successful instances of gesture use, which we describe as having goal–outcome matches. In this study, 28 orangutans in three European zoos were observed for 9 months. We distinguished 64 gestures on structural grounds, 40 of which had frequent goal–outcome matches and could therefore be analysed for meaning. These 40 gestures were used predictably to achieve one of 6 social goals: to initiate an affiliative interaction (contact, grooming, or play), request objects, share objects, instigate co-locomotion, cause the partner to move back, or stop an action. Twenty-nine of these gestures were used consistently with a single meaning. We tested our analysis of gesture meaning by examining what gesturers did when the response to their gesture did not match the gesture’s meaning. Subsequent actions of the gesturer were consistent with our assignments of meaning to gestures. We suggest that, despite their contextual flexibility, orangutan gestures are made with the expectation of specific behavioural responses and thus have intentional meanings as well as functional consequences.

Abstract: Altruism poses a problem for evolutionary biologists because natural selection is not expected to favor behaviors that are beneficial to recipients, but costly to actors. The theory of kin selection, first articulated by Hamilton (1964), provides a solution to the problem. Hamilton's well-known rule (br > c) provides a simple algorithm for the evolution of altruism via kin selection. Because kin recognition is a crucial requirement of kin selection, it is important to know whether and how primates can recognize their relatives. While conventional wisdom has been that primates can recognize maternal kin, but not paternal kin, this view is being challenged by new findings. The ability to recognize kin implies that kin selection may shape altruistic behavior in primate groups. I focus on two cases in which kin selection is tightly woven into the fabric of social life. For female baboons, macaques, and vervets maternal kinship is an important axis of social networks, coalitionary activity, and dominance relationships. Detailed studies of the patterning of altruistic interactions within these species illustrate the extent and limits of nepotism in their social lives. Carefully integrated analyses of behavior, demography, and genetics among red howlers provide an independent example of how kin selection shapes social organization and behavior. In red howlers, kin bonds shape the life histories and reproductive performance of both males and female. The two cases demonstrate that kin selection can be a powerful source of altruistic activity within primate groups. However, to fully assess the role of kin selection in primate groups, we need more information about the effects of kinship on the patterning of behavior across the Primates and accurate information about paternal kin relationships.