Exploring aggression regulation in managed groups of horses<i>Equus caballus</i>

International audienceHorses are highly social animals that have evolved to live in social groups. However, in modern husbandry systems, single housing prevails where horses experience social isolation, a challenge-to-welfare factor. One major reason for this single housing is the owners' concerns that horses may injure each other during aggressive encounters. However, in natural conditions, serious injuries due to aggressive encounters are rare. What could therefore explain the claimed risks of group living for domestic horses? Basing our questioning on the current knowledge of the social life of horses in natural conditions, we review different practices that may lead to higher levels of aggression in horses and propose practical solutions. Observations of natural and feral horses mostly indicate a predominance of low frequencies and mild forms of aggression, based on subtle communication signals and ritualized displays and made possible by group stability (i.e. stable composition), dominance hierarchy and learning of appropriate social skills by young horses. Obviously, adults play a major role here in canalizing undesirable behaviours, and social experience during development, associated with a diversity of social partners, seems to be a prerequisite for the young horse to become socially skilled. Given the natural propensity of horses to have a regulation of aggression in groups, the tendency to display more aggression in groups of domestic horses under some management practices seems clearly related to the conditions offered. We therefore review the managing practices that could trigger aggressiveness in horses. Non social practices (space, resource availability) and social practices (group size, stability of membership, composition and opportunities for social experiences during development) in groups of domestic horses are discussed here. Finally, we propose simple practical solutions leading to more peaceful interactions in groups of domestic horses, based on the knowledge of horses' natural social life which therefore should be enhanced (e.g. ensuring roughage availability, favouring group stability, introducing socially experienced adults in groups of young horses, etc.). The state of the art indicates that many questions still need to be answered. Given the importance of the associated welfare issues and the consequences on the use of horses, further research is required, which could benefit horses ... and humans. (C) 2012 Elsevier B.V. All rights reserved

Olive baboons, Papio anubis, adjust their visual and auditory intentional gestures to the visual attention of others

International audienceAlthough nonhuman primates' gestural communication is often considered to be a likely precursor of human language, the intentional properties in this communicative system have not yet been entirely elucidated. In particular, little is known about the intentional nature of monkeys' gestural signalling and related social understanding. We investigated whether olive baboons can (1) adjust their requesting gestures to the visual attention of the experimenter with special emphasis on the state of the eyes (open versus closed), and (2) flexibly tailor visual and auditory-based gestures to elaborate their communication as a function of whether or not the experimenter can see them. Using a food-requesting paradigm, we found monkeys able to favour either visual or auditory-based requesting gestures to match the experimenter's visual attention. Crucially, when the human was not visually attending, they silenced visual gestures to some extent but performed more attention-getting gestures. This is, to our knowledge, the first report of monkeys elaborating attention-getting signals to compensate for communication breakdown. Gestural communication was also supported by gaze alternation between the experimenter's face and the food, especially when the human was visually attending. These findings offer evidence that olive baboons understand the state of the eyes in others' visual attention and use requesting gestures intentionally. They emphasize that Old World monkeys shift to acoustic communication when the recipient is not visually attending. In contrast to that of human infants and great apes, this acoustic communication is purely gestural, not vocal

Is leadership a reliable concept in animals? An empirical study in the horse

International audienceLeadership is commonly invoked when accounting for the coordination of group movements in animals, yet it remains loosely defined. In parallel, there is increased evidence of the sharing of group decisions by animals on the move. How leadership integrates within this recent framework on collective decision-making is unclear. Here, we question the occurrence of leadership in horses, a species in which this concept is of prevalent use. The relevance of the three main definitions of leadership - departing first, walking in front travel position, and eliciting the joining of mates - was tested on the collective movements of two semi-free ranging groups of Przewalski horses (Equus ferus przewalskii). We did not find any leader capable of driving most group movements or recruiting mates more quickly than others. Several group members often displayed pre-departure behaviours at the same time, and the simultaneous departure of several individuals was common. We conclude that the decision-making process was shared by several group members a group movement (i.e., partially shared consensus) and that the leadership concept did not help to depict individual departure and leading behaviour across movements in both study groups. Rather, the different proxies of leadership produced conflicting information about individual contributions to group coordination. This study discusses the implications of these findings for the field of coordination and decision-making research

Adult-Young Ratio, a Major Factor Regulating Social Behaviour of Young: A Horse Study

Adults play an important role in regulating the social behaviour of young individuals. However, a few pioneer studies suggest that, more than the mere presence of adults, their proportions in social groups affect the social development of young. Here, we hypothesized that aggression rates and social cohesion were correlated to adult-young ratios. Our biological model was naturally-formed groups of Przewalski horses, Equus f. przewalskii, varying in composition.We investigated the social interactions and spatial relationships of 12 one- and two-year-old Przewalski horses belonging to five families with adult-young ratios (AYR) ranging from 0.67 to 1.33. We found striking variations of aggression rates and spatial relationships related to the adult-young ratio: the lower this ratio, the more the young were aggressive, the more young and adults segregated and the tighter the young bonded to other young.This is the first study demonstrating a correlation between adult-young ratios and aggression rates and social cohesion of young individuals in a naturalistic setting. The increase of aggression and the emergence of social segregation in groups with lower proportions of adults could reflect a related decrease of the influence of adults as regulators of the behaviour of young. This social regulation has both theoretical and practical implications for understanding the modalities of the influence of adults during ontogeny and for recommending optimal settings, as for instance, for schooling or animal group management

Investigating determinants of yawning in the domestic (Equus caballus) and Przewalski (Equus ferus przewalskii) horses

International audienceYawning is rare in herbivores which therefore may be an interesting group to disentangle the potential function(s) of yawning behaviour. Horses provide the opportunity to compare not only animals living in different conditions but also wild versus domestic species. Here, we tested three hypotheses by observing both domestic and Przewalski horses living in semi-natural conditions: (i) that domestic horses may show an elevated rate of yawning as a result of the domestication process (or as a result of life conditions), (ii) that individuals experiencing a higher level of social stress would yawn more than individuals with lower social stress and (iii) that males would yawn more often than females. The study involved 19 Przewalski horses (PHs) and 16 domestic horses (DHs) of different breeds living in large outdoor enclosures. The results showed that there was no difference between the PH and DH in yawning frequency (YF). PHs exhibited much higher levels of social interactions than DHs. There was a positive correlation between yawning frequency and aggressive behaviours in PHs, especially males, supporting the idea that yawning may be associated with more excitatory/stressful social situations. A correlation was found between yawning frequency and affiliative behaviours in DHs, which supports the potential relationship between yawning and social context. Finally, the entire males, but not castrated males, showed much higher levels of yawning than females in both species. The intensity (rather than the valence) of the interaction may be important in triggering yawning, which could therefore be a displacement activity that helps reduce tension

Sociogenèse et expression des comportements individuels et collectifs chez le cheval

Ce travail porte sur l’influence des congénères dans la régulation du comportement social chez le cheval. Un premier aspect de l’étude développe l’influence de l’environnement social sur l’acquisition des compétences sociales des jeunes, puis leurs conséquences sur le succès reproducteur précoce des étalons. Nos résultats montrent que le comportement des jeunes chevaux de Przewalski peut être associé à certaines caractéristiques de leur groupe natal, comme le ratio jeune/adulte du groupe. Au sein de la famille, le développement de leur réseau de relations s’accompagne d’une différenciation des interactions sociales des jeunes avec leurs différents partenaires jeunes et adultes, susceptibles de constituer des voies d’influences sociales complémentaires. L’influence des adultes non-apparentés sur le comportement des jeunes a été mise en évidence au travers d’une approche expérimentale sur des chevaux domestiques de même âge. Nos résultats indiquent un effet de l’interaction entre la présence de jeunes et d’adultes dans la sociogenèse des jeunes chevaux. En outre, un lien prédictif entre le rang hiérarchique des étalons célibataires et le nombre de poulains qu’ils conçoivent ultérieurement, a été mis en évidence dans la population de chevaux de Przewalski, suggérant d’importantes conséquences fonctionnelles au développement des compétences sociales des mâles. Enfin, ce travail explore les processus décisionnels impliqués dans les déplacements des familles de chevaux de Przewalski. Il s’avère que les chevaux effectuent des décisions collectives auxquelles les adultes participent plus que les jeunes. La coordination sociale des groupes y est affectée par des facteurs environnementaux. Nos résultats indiquent que les chevaux sont susceptibles d’effectuer un compromis entre leurs motivations individuelles et le maintien de la cohésion sociale. Certains individus plus influents, pourraient faire bénéficier au groupe d’une meilleure connaissance de l’environnement. Dans l’ensemble, ce travail contribue à une meilleure compréhension du rôle des influences sociales intra- et inter-générationnelles dans l’acquisition des compétences sociales et dans le fonctionnement des groupes.This study deals with the role of social influences on the regulation of social behaviour in horses. Our primary interest was how the social environment at early stages of development affected the development of social skills of young horses and its functional consequences on the early reproductive success of stallions. The results show that the behaviour of young Przewalski horses correlates with some features of their natal group, such as the young/adult ratio. Within families, the development of young’s social preferences occurs with a differentiation of social relationships according to interacting partners. This suggests that both young and adult partners may constitute important and complementary social influences in the social development of young animals. Influences of an adult presence, tested in same-age domestic horses, reveal immediate effects on social relationships between young horses. These findings indicate interacting effects of the presence of young and adult partners in the young horses’ sociogeny. Additionally, a predictive link between stallion dominance rank in allmale groups and their subsequent paternities until six –years old suggests there are important functional consequences of the development of males’ social skills. The second part of this study investigates decision-making processes in the collective movements of Przewalski horse families. Przewalski horses perform collective decisions in which adults contribute more than young horses, suggesting they have a better knowledge of their environment. Indeed, the social dynamics of movement patterns are affected by environmental factors and the horses make compromises between their own motivations and social cohesion. Overall, this study contributes to a better understanding of intra- and intergenerational social influences in animals, and their role in the acquisition of social skills in young horses and in functioning of social groups

Le pointage controversé des singes : éléments empiriques chez le babouin olive (Papio anubis)

National audiencePointing gestures have been intensively studied by psychologists in both human and non-human primates. Research usually focusses on the emergence of pointing during ontogeny and phylogeny because infants develop pointing before speaking and non-human primates use pointing or “point-like gestures” while they do not (yet) speak. However, pointing in non-humans remains controversial. In this regard, Tomasello (2006) wrote “Why don’t apes point?”, putting forward that non-human pointing may not encapsulate similar functional and cognitive properties as do human pointing. However, empirical studies on non-human primates’ gestural communication have led to remarkable results that put this claim for human uniqueness back into question. I will base the present contribution on a series of empirical studies conducted on olive baboons (Papio anubis) to illustrate this issue of pointing gestures in monkeys. I will emphasize the communicative function and intentional properties of such gestures, as well as the cognitive skills implemented for their use. These studies show that monkeys flexibly tailor their gestural communication to the attentional state of their audience, and show persistency, targeted attention, and skills for elaborating their communicative means. However, the findings centered on the acquisition processes stress the importance of the context in which gesturing develops; only monkeys that learn to gesture towards an attentive and responsive human eventually develop skills for intentional communication closely similar to ours. These results are discussed in terms of operational criteria that may be relevant to the study of intentional communication, and in relation to the conceptual postures of lean and rich interpretations in comparative psychology