Friend or Foe?

I’m hoping you guys can help me with a question that has been on my mind.

We all know when horses meet for the first time they decide within moments to be friends or not. They go through the “introduction ritual” then they’ll either gallop off together or, one will chase the other away. I’ve seen it a thousand times.

In addition, I’ve witnessed horses who have zero tolerance for each other eventually make a change to become friends over days, weeks, or months. I even have some tricks up my sleeve to help facilitate horses to bond after an initial exchange of insults and threats.

But what I have never seen is a horse unfriend another horse. I have never seen horses who bond at first and later become foes. They may have minor falling outs when resources are limited, eg, arguing over the last bite of hay. But never have I seen horses that once got along turn into mortal enemies. 

I’ve observed the relationship between two horses weakened by the introduction of the third horse. It is common for the friendship of two horses to be interrupted when a third horse enters the group and bonds with one of the horses. But even in that case, the friendship is not broken.

I have just never seen horses unfriend each other.
Have you? I’d appreciate hearing your experiences and thoughts on the subject.