Q: My 6-year-old mare gets turned out daily with another older mare that she’s been paired with for about three years. When I take my mare in to ride, the other one screams and nickers for her and becomes very excited when we return to the field. Once back together, however, the older mare chases, bites, and kicks at my mare for about five minutes as if she’s punishing her for leaving! What is this behavior?

—Elise, via email

A: Because the behavior you describe could represent different types of underlying motivation, it would be best to see a video example to answer that question with much certainty. Interpretation would depend upon whether it looks like the older mare seems to be trying to herd the returning mare away from the gate, as if to say, “Stay here and don’t leave,” or herding her away from some guarded resource like the waterer or hay rack. As crazy as it sounds, some horses can seem stressed when a companion leaves but quickly adopt the resources in the field as their own and not be shared with a returning herdmate. And crazier yet, as you imply, they do that over and over again, every time they are separated. I can say that it is unlikely that the older mare intends her response as punishment. But a better understanding may lead to some suggestions of strategies for managing both the apparent separation stress and the aggression upon reuniting.