Abstract: The aim of this study was to investigate the impact of training experience on young horses (Equus caballus)’ lateralized responses to an approaching human. The results show that the one year old untrained horses display asymmetrical responses to an approaching human, with more negative reactions (escapes, threats) when approached from the left side, while approaches towards the right shoulder elicited more positive behaviors. On the contrary, two years old trained horses reacted equally positively to approaches and contact on both sides. Our findings support those of previous studies investigating a link between emotionality and laterality and confirm the role of the left hemisphere in the processing of novel or negative stimuli. Moreover, the data underline the impact work and training can have on this laterality in horses.

Abstract: <sec> <title>Background</title> <p>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, <italic>Equus f. przewalskii</italic>, varying in composition.</p> </sec><sec> <title>Methodology/Principal Findings</title> <p>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.</p> </sec><sec> <title>Conclusion/Significance</title> <p>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.</p> </sec>

Abstract: <sec> <title>Background</title> <p>Animals' ability for cross-modal recognition has recently received much interest. Captive or domestic animals seem able to perceive cues of human attention and appear to have a multisensory perception of humans.</p> </sec> <sec> <title>Methodology/Principal Findings</title> <p>Here, we used a task where horses have to remain immobile under a vocal order to test whether they are sensitive to the attentional state of the experimenter, but also whether they behave and respond differently to the familiar order when tested by a familiar or an unknown person. Horses' response varied according to the person's attentional state when the order was given by an unknown person: obedience levels were higher when the person giving the order was looking at the horse than when he was not attentive. More interesting is the finding that whatever the condition, horses monitored much more and for longer times the unknown person, as if they were surprised to hear the familiar order given by an unknown voice.</p> </sec> <sec> <title>Conclusion/Significance</title> <p>These results suggest that recognition of humans may lie in a global, integrated, multisensory representation of specific individuals, that includes visual and vocal identity, but also expectations on the individual's behaviour in a familiar situation.</p> </sec>

Abstract: <p>Leadership 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 (<italic>Equus ferus przewalskii</italic>). 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.</p>

Abstract: Some behaviours remain a mystery and their determinants are still uncertain. Here we propose a critical interpretation of two puzzling behaviours, i.e. yawning and adult play, recorded in large samples of domestic horses kept in sub-optimal conditions (e.g. time-restricted feeding practices, social isolation). Yawning is involved in behavioural state changes, especially in quiet contexts of motor relaxation, but seems also to be triggered by stress and emotional contexts. Thus, we investigated specific correlates of yawning and stereotypic behaviours in two large samples of working horses (n1 = 87, n2 = 59). A clear co-occurrences of yawning and stereotypic behaviours appeared: stereotypic horses yawned more than the non-stereotypic horses (Fisher test, p < 0.02), yawning increased at the same time periods as stereotypic behaviours did (Wilcoxon tests, p < 0.05 to 0.001) and yawning frequency was even sometimes positively correlated with stereotypic behaviour frequencies (Spearman correlations, p < 0.005). Play, more typical of young stages in healthy individuals, occurs rarely at adult stages but then more often in captive/domestic animals (which can be challenging to welfare) than in animals living in natural conditions. Thus, we tested the hypothesis that adult play may reflect altered welfare states in horses, where, as in several species, play rarely occurs at adult stages in natural conditions. We observed the behaviour (in particular social play) of 29 adult riding school horses during occasional outings in a paddock and measured several stress indicators (health-related, behavioural and physiological) when these horses were in their home individual boxes. Results revealed that the number of horses and rates of adult play appeared very high compared to field report data and that most stress indicators measured differed between “players” and “non-players”, revealing that most “playful” animals were more prone to suffer from chronic stress contrarily to “non-playful” horses (Fisher, Chi-square, Mann-Whitney and Spearman correlation tests, p < 0.05 to 0.001). Altogether, these results show that yawning and adult play can both reflect altered welfare states in horses, highlighting that these puzzling behaviours should not be considered, as currently thought, as reliable indicators of good welfare states and / or expression of positive emotions.