Horses evolved to live in highly social groups; however in many countries it is traditional to keep them individually in stables, or turned out singly in paddocks. It is becoming increasingly understood that this causes health and behaviour problems, including aggression. In contrast, aggressive encounters are rare in properly introduced, established groups, where management meets the needs of equids as a species. These three papers explore management practices that may affect the risk of aggressive encounters, and analyse adult:young ratios and how they facilitate social cohesion.
Bourjade, M. et al. (2008) ‘Could adults be used to improve social skills of young horses, Equus caballus?’, Developmental Psychobiology 50:4 408-17 http://www.unboundmedicine.com/medline/citation/18393282/ Could_adults_be_used_to_improve_social_skills_of_young_horses_Equus_caballus
Bourjade M, de Boyer des Roches A, Hausberger M (2009) ‘Adult-young ratio, a major factor regulating social behaviour of young: a horse study’ PLoS ONE 4(3): e4888. doi:10.1371/journal.pone.0004888
Furieux, C. et al. (2012) ‘Exploring aggression regulation in managed groups of horses Equus caballus’, Applied Animal Behaviour Science,3:4: 216-228 http://yadda.icm.edu.pl/yadda/element/bwmeta1.element.elsevier-36cb881c-2bf5-3662-8e11-ce6e3a57ebd3