Abstract: Abstract. Considerable evidence across many taxa demonstrates that prior social experience affects the outcome of subsequent aggressive interactions. Although the 'loser effect', in which an individual losing one encounter is likely to lose the next, is relatively well understood, studies of the 'winner effect', in which winning one encounter increases the probability of winning the next, have produced mixed results. Earlier studies differ concerning whether a winner effect exists, and if it does, how long it lasts. The variation in results, however, may arise from different inter-contest intervals and procedures for selecting contestants employed across previous studies. These methodological differences are addressed through a series of experiments using randomly selected winners and three different inter-contest intervals in the pumpkinseed sunfish, Lepomis gibbosus. The results indicate that a winner effect does in fact exist in pumpkinseed sunfish, but that it only lasts between 15 and 60 min. Based on these results, predictions about the behavioural dynamics of hierarchy formation are discussed, and it is suggested that it may be impossible, in principle, to predict the outcome of dominance interactions between some individuals before they are actually assembled to form a group. Finally, the possible mechanisms underlying the winner effect are explored.

Abstract: Abstract. In animals capable of learning from a parent or other individual, socially acquired behaviour can be transmitted through several generations. When the inheritance of variations in such behaviour is independent of genotypic variations, natural selection can operate on an additional level. Direct evolution of behaviour becomes possible, and this may alter the estimates of costs and benefits of behaviour patterns for the individual who transmits them. It is suggested that the effects of maternally transmitted behaviour contribute to the evolution of maternal behavioural strategies, and to the evolution of behaviour associated with male-female conflict.

Abstract: Abstract. Peaceful interventions in conflicts are an extremely rare phenomenon in most primate species. In contrast to aggressive interventions, they cannot lead to gains in terms of competition. To clarify the function and origin of this behaviour, the patterning and consequences of peaceful and aggressive interventions were studied in a semi-free ranging group of tonkean macaques, Macaca tonkeana. Intense conflicts frequently elicited both types of intervention. Interveners preferentially targeted the initiator of the conflict, who was generally the dominant of the two opponents. Males tended to intervene more than females, especially using peaceful interventions. Interventions were frequently performed on behalf of the most closely kin-related opponent; this was true particularly for aggressive interventions. In peaceful interventions, the intervener was usually dominant over both parties. Lipsmacking, clasping, mounting and social play were mainly used, and were successful in halting aggression. Peaceful interventions were frequently followed by an affinitive interaction, such as grooming, between intervener and target. Peaceful interventions thus appear to protect the beneficiary while preserving the social relationship between intervener and target. The origin of the behaviour can be traced to the epigenetic constraints arising from the species-specific social organization.

Abstract: Abstract. The relation between memory for travel time and foraging decisions was studied experimentally. The temporal properties of two environments with patchily distributed food were simulated in the laboratory using pigeons, Columba livia, as subjects. The two environments differed in mean travel time, while the coefficient of variation of travel time and the decelerated function relating cumulative food gain to time in the patch were held constant within and between environments. Each environment contained a uniform mixture of five travel times experienced in a random order. Two of the five travel times were common in both environments. Effects of travel time were studied by comparing prey collected per patch visit (PPV) after various travel times within each environment, and by comparing patch exploitation after equal travel times between environments. Within the environment with long mean travel time (LMT) PPV was positively correlated with the last and the penultimate travel times but not with travel times before that. The increase in PPV per second of last travel time was six times greater than the increase per second of penultimate travel time, implying very steep memory discounting. In the environment with short mean travel time (SMT), there was no correlation between PPV and previous travel times. However, comparisons between environments of visits following travel times common to both environments (thus removing the effect of the last travel time) showed that substantially more prey were taken after equal travel times in the LMT than in the SMT environment. This difference cannot be accounted for by the within-environment effect of penultimate travel time, implying that there is a different, less steeply devalued, effect of the mixture of travel times. A model of information processing based on combining Scalar Expectancy Theory with the predictions of rate maximization under the Marginal Value Theorem is presented. The model can approximate the results obtained in this and previous experiments and provides a framework for further analysis of memory mechanisms of foraging behaviour.

Abstract: According to the socioecological framework, transitivity (or linearity) in dominance relationships is related to competition over critical resources. When a population is structured into groups, the intensity of between- versus within-group competition influences the form and function of its social organization. Few studies have compared the type and relative intensity of competition at these two levels. African elephants have well-structured social relations, providing an exemplary system for such a study. We report on dominance hierarchies among free-ranging elephants and evaluate the factors that drive their socioecological structure to lie in a region of the three-dimensional nepotism/despotism/tolerance space rarely observed among social species; namely, where non-nepotistic, transitive dominance hierarchies within groups emerge despite kin-based philopatry and infrequent agonistic interactions over widely distributed resources. We found significant transitivity in dominance hierarchies between groups. Dominance relations among the matriarchs of different social groups were primarily age based, rather than driven by physical or group size, and group matriarch rank influenced the dominance relationships among nonmatriarchal females in the population. Our results suggest that between-group dominance relationships induce tolerance among group members, which in combination with high group relatedness, reduces the benefits of nepotism. We postulate that cognitive abilities and high risk of injury in contests enhance winner and loser effects, facilitating the formation of transitive dominance relationships, despite widely distributed resources over which infrequent competition occurs. The interplay of cognitive abilities, winner and loser effects, resource distribution, and within- and between-group dominance relationships may produce behaviour in other strongly social mammals that differs from that predicted by a superficial application of current socioecological models.