My 16'2 thoroughbred mare has started to become over protective of my 10'2 pony. She is fine with the bigger horses in the field but as soon my little one goes to see another of the smaller ponies she goes mad rounding her up away from them,( the two smaller ponies are a similar hight and color and also mares) It’s as if she thinks she is her mum. My tb goes mad if my pony is left in the field without her or she is taken out of her sight but she is more than happy to leave my pony if it is in its stable. Could it be possible she thinks my pony is her foal? and what is the best way to stop this behavior before injuries happen. She does not display this behavior towards humans or the other horses just the 2 other ponies.
Do you have any way to stable these animals separately? The mare obviously has developed an intense attachment to your pony. I have worked with horses like this, using ground work techniques, some I have developed, some of Tellington's T.E.A.M. methods, and have been successful in getting such an animal to pay attention to me when I am working with her (all methods are non-abusive) but it is a problem to correct her behavior when she is just out in the field with your horses.
Your horses may work it all out......your other horses will learn to stay away, but there still could be harm done to them by the mare if they get in her way. If this behavior happened gradually, could you possibly ask a friend to stable either your mare or the pony away from you for a while? The pecking order could change a bit while one of the pair is gone.
There could be a hormonal change going on with your mare to make her more aggressive than she used to be. If you send me your email, I could forward a research article on agression in horses that I just read.