Even a pair of horses will establish some kind of subtle or overt hierarchical arrangement. | Photo: iStock

A: Introducing two horses is something a lot of horse owners don’t relish, and adding a new horse to an established herd can really up anxiety. I don’t know if there’s any one best way, because not only do farm resources differ, but individual horse temperaments play a role, too.

This is not just an issue of domesticated horses. Feral horses have introductory events, too. We see posturing and sometimes fighting between harem and bachelor band stallions at meet-ups or challenges. Fillies usually leave their home band and join another, and agonistic encounters with established members can occur until they settle into the hierarchy.

Domestic horses living in groups form hierarchies that are linear but often with triangulations, and also the dominant horses might vary according to resources and activities. Once established, a hierarchy tends to remain stable and most agonistic encounters we see are threats or avoidance behaviors. Not only do we see dominant and subordinate relationships, but we see tolerance or preferences by a dominant with more subordinate individuals