Question: We are new owners of a 16 yr. old Arabian mare.  She is wonderful.  We actually rescued her from Animal Rescue.  She has been at her new stable/barn for a week and getting used to the other horses.  Our question~ another mare has taken a liking to her and this mare is in heat.  This other mare paces like crazy if we separate them.  The reason we separate them for now is our mare needs to take the pasture in small doses till she is feeding for longer periods of time.  I thought this other mare was protecting her from the rest of the herd, but curious what you think and is this normal behavior. 

 Answer:  While you mentioned that the other mare is in heat, this may or may not have impacted how quickly the mares bonded. Cows often attempt to mount other cows that are in heat as they themselves approach heat. This behavior is not commonly seen in mares. I believe what has happened is that your mare has found a buddy with whom she bonded quickly. If the other mare did not have a buddy when your mare was introduced to the barn, it is likely they bonded quickly for this reason. Many horses seem to have one particular buddy, and certain horses are more prone to seek out the company of a particular buddy more than others. Even though your mare has not been buddies with this other mare for very long, they appear to have bonded well. When your mare is taken away after her period of grazing, the other mare paces the fence due to anxiety as her buddy leaves the pasture. I do not think the other mare was protecting her from the herd, so much as simply buddying up with your mare. Good luck on working with your rescued mare.