Abstract: Horses 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.

Abstract: Wounding in an 83-member group of rhesus macaques (Macaca mulatta) housed at the Yerkes Regional Primate Research Center Field Station became excessive to the point that intervention was deemed necessary. When observations indicated that three females from the group's alpha matriline were principally responsible for the wounding, the matriline (N = 7) was removed from the group. This study was conducted to document an atypical pattern of wounding in this group and to evaluate the effectiveness of removal as a procedure for controlling injuries. The aggression rates of 21 adult subjects and the wounds of all group members were recorded before and after the removal procedure and compared with those in a similar-sized group. Removing the alpha matriline did not alter aggression rates in the group or the rank order among the remaining matrilines. Aggression rates in the experimental group were also not significantly different from those in the comparison group before or after the removal. With the alpha matriline present, wounding levels in the group were significantly higher than those in the comparison group. After removal of the matriline, the frequency of wounds decreased significantly to levels similar to those of the comparison group. The pattern of excess wounding attributed to the extracted alpha females was idiosyncratic, involving removal of large patches of skin from the hindquarters of adult females or removal of the distal portion of the fingers, toes, or tail from juveniles.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract: Social dominance develops more slowly when young animals are kept in intact peer groups where they need not compete for resources. Learned generalizations may cause smaller and weaker animals to accept subordinate status readily when confronted with strangers that would be formidable opponents. Sexual hormones and sensitivity to them can influence the onset of aggression and status attained. After dominance orders are established, they tend to be stable in female groups but are less so in male groups. Psychological influences can affect dominance relationships when strangers meet and social alliances within groups may affect relative status of individuals. Whether status associated with agonistic behavior is correlated with control of space and scarce resources needs to be determined for each species and each kind of resource. When such correlations exists, competitive tests and agonistic behavior associated with gaining access to scarce resources can be useful to the observer in learning about dominance relationships rapidly. Examples are given to illustrate how estimates of social dominance can be readily attained and some strengths and weaknesses of the various methods.

Abstract: Patterns of aggressive and affiliative behavior, such as counter aggression and reconciliation, are said to covary in the genus Macaca; this is referred to as the systematic variation hypothesis. These behavior patterns constitute a species dominance style. Van Schaik's [1989] socioecological model explains dominance style in macaques in terms of within- and between-group contest competition. Dominance style is also said to correlate with phylogeny in macaques. The present study was undertaken to examine phylogenetic and socioecological explanations of dominance style, as well as the systematic variation hypothesis. We collected data on counter aggression and reconciliation from a habituated group of Assamese macaques (Macaca assamensis) at the Tukeswari Temple in Assam, India. The proportion of agonistic episodes that involved counter aggression was relatively low. Counter aggression, however, occurred more often among males than among females, and it was most common when females initiated aggression against males. The conciliatory tendency for this group of Assamese macaques was 11.2%. The frequency of reconciliation was low for fights among males and for fights among females, but reconciliation was particularly rare for opposite-sexed opponents. Female social relationships were consistent with the systematic variation hypothesis, and suggest a despotic dominance style. A despotic dominance style in Assamese macaques weakens the correlation between dominance style and phylogeny in macaques, but it is not inconsistent with the socioecological model. Male-female relationships were not well explained by the despotic-egalitarian framework, and males may well have more tolerant social relationships than do females. Sex differences need to be considered when categorizing species according to dominance style.

Abstract: Viele Pferdebesitzer bevorzugen aus Angst vor aggressiven Interaktionen und Verletzungsgefahr der Tiere untereinander die Einzelhaltung, obwohl von Tierschutzorganisationen die Gruppenhaltung für Pferde empfohlen wird. In dieser Studie beobachteten wir während des alltäglichen Soziallebens als auch bei der Eingliederung von neuen Gruppenmitgliedern das Sozialverhalten, insbesondere das Aggressionsverhalten, von elf Gruppen domestizierter Pferde (Equus caballus) verschiedener Größe und Zusammensetzung. Während des alltäglichen Soziallebens hatten die Gruppe und der Paddock-Typ (Gras / kein Gras) keinen Einfluss auf die Verhaltensweisen, wohingegen die Paddockgröße unter 10000 m2 einen signifikanten Einfluss auf die submissiven Verhaltensweisen (GzLM; n=56; t=-2.061, P=0.044) und einen nicht signifikanten Einfluss auf die aggressiven Verhaltensweisen (GzLM; n=56; t=-1.782, P=0.081) hatte. Allerdings verringerten sich sowohl die aggressiven als auch die submissiven Verhaltensweisen mit steigendem Platzangebot bis zu 10000 m2 (Spearman rank Korrelation; n=56; aggressive Verhaltensweisen: r = -0.313, P = 0.019; submissive Verhaltensweisen: r = -0.328, P = 0.014). Während den Eingliederungen reduzierten sich die Aggressionen pro Stunde mit der Vergrößerung des Platzangebotes (Spearman rank Korrelation; n=28; r=-0.402, P=0.034). Dies zeigte sich noch deutlicher, wenn Beobachtungen mit einem Platzangebot von über 10000 m2 ausgeschlos- sen wurden (Spearman rank Korrelation; n=23; r=-0.549, P=0.007). Während des alltäglichen Soziallebens näherte sich der Aggressionslevel der Nulllinie an, wenn das Platzangebot pro Pferd mehr als 331 m2 betrug. Deshalb empfehlen wir zur Reduzierung des Aggressionslevels und des Verletzungsrisikos von sozial gehaltenen Pferdegruppen ein Platzangebot von mindestens 331 m2 pro Pferd.
[Even though animal welfare organisations propose group housing for horse welfare, many owners stable horses individually for fear of aggressive interactions and injury risks. In the present study we observed social behaviour, and especially aggressiveness, in eleven domestic horse groups (Equus caballus) of different size and composition, in basic social situations and when new group members were introduced. During basic social situations, the group and the type of paddock (grass / no grass) had no effect on any of the behaviours, where- as the enclosure size below 10,000 m2 had a significant effect on submissive behaviour (GzLM; n=56; t=-2.061, P=0.044) and an insignificant effect on aggressive behaviour (GzLM; n=56; t=-1.782, P=0.081). However, aggressive and submissive behaviour dimi- nished with the increase of enclosure sizes up to 10,000 m2 (Spearman rank correlation; n = 56; aggressive behaviour: r = -0.313, P=0.019; submissive behaviour: r=-0.328, P=0.014). During introductions, aggression levels per hour decreased with any increase of enclosure size (Spearman rank correlation; n=28; r=-0.402, P=0.034) and even more when enclosure sizes above 10,000 m2 were excluded (Spearman rank correlation; n=23; r=-0.549, P=0.007). During basic social situations the aggression level approached zero when the space allowance was more than 331 m2 per horse. We therefore recommend keeping horse groups in an enclosure with at least 331 m2 per horse to reduce aggression and injuries.]