Commentary

Spontaneous Rearing and Food Aggression in Horses

Spontaneous Rearing and Food Aggression in Horses

Some rearing behavior in horses is play initiation, which is common among orphans.

Photo: iStock

Q. My 3-year-old Appaloosa mare is showing spontaneous odd behavior. I have owned her for about eight months, and I have known her since she was 2. Her former owner didn’t treat her well, chased her into her yard at feed times, etc.

Now she is rearing over me. She has done this three times in her yard and twice on the lead. I would start cleaning her yard, turn my back, and she would rear. There is no aggression toward me, and there is no warning sign that she will rear. Her ears are forward, there’s no striking action, she simply rears, comes down, lets out a sigh, and comes toward me for a pat or just walks away. I do tell her off when she does this.

She used to have a yard next to a yearling filly. She would rear and kick out at her and become very aggressive toward food. Since taking the filly away and placing my mare next to a gelding, this behavior has stopped. She still shows slight aggression toward food, but it has improved. If she is in a paddock with any horse she will attack them. 

She has not shown signs of coming into season. I have been to the vet, and she has been cleared of any tumors/cysts on her ovaries. She does have a very large follicle on her ovaries as well has two others behind it. The vet has given her (deslorelin) and Regu-Mate to see if this makes a difference. The vet says it seems like orphan behavior, but she was brought up in a paddock of foals and mares. 

My mare is quiet under saddle and on the ground, and she shows no signs of aggression toward other horses when I am riding or holding her on the ground.  

What should I do? As it is so spontaneous, I have no warning signs when this will happen. I am not scared of her, but I have become more cautious around her.

Olivia Hoogenhout, Woodville, South Australia


A. Let me first comment on the rearing. It is difficult to say much without seeing it in progress, but the rearing near you when you are cleaning the yard and otherwise not paying attention to her sounds like it could be play initiation behavior toward you. As your veterinarian suggested, this type of interaction with humans is a common problem in orphans. While difficult to explain, this behavior has an odd characteristic about it—you sort of know it when you see it. Orphans, especially when hand-fed, tend to become overly interested and bonded to people and interact with people as they would with other horses. It is more common in orphans, but nonorphans can also show similar behavior suggesting being “overly bonded” to people. It is typically more of a problem and more difficult to deal with in males than females. This type of behavior is challenging to eliminate, but the best recommendation for trying to eliminate any undesirable behavior is to try to prevent stimulating it, and if it happens, ignore it and redirect to a more desirable behavior.

Even if this is play initiation rearing, it is no doubt dangerous. The easiest way to stay safe and avoid inadvertently reinforcing the behavior with your reaction is to avoid the situations that provoke the behavior. So for cleaning the yard, if your mare ties, you could tether her away from where you are working. If she doesn’t tie well, you could simply contain her in a separate enclosure. For example, you can create a small sub-enclosure quite inexpensively using a gate or round pen panel mounted to be able to swing across a corner of the paddock. If neither of those are possible, you could establish a routine of giving her a fresh flake of hay in a far corner, keeping her focused on eating while you clean. Of course, I would make sure to keep an eye on her. If she should approach, just ignore her and leave, so as not to reinforce her invitation to play by any interaction, verbal or physical. 

For the rearing when being led, here’s what I have found to be most effective for trying to prevent it: Just try to walk on with purpose. Mentally map out the route you plan to walk, and walk forward without hesitation and with focused determination on your destination. Keep a slight amount of slack on the lead (so, no pressure on the halter), allowing the horse to follow your footsteps. This should hold the horse’s focus on walking forward rather than rearing. Should the horse rear, try not to react. For horses with a tendency to rear, I like to use a long soft cotton lead that can be held with slight slack and a loose grip and be ready to release some length to slide smoothly if the horse should rear. In a nutshell, the goal is:

  1. “Give the horse her head” as she rears, so as to avoid any pressure on the halter as she goes up. Pressure only exacerbates the rearing. 
  2. Almost simultaneously, if in harm’s way, step quietly to one side or another. 
  3. And as soon as her forelimbs touch the ground, just walk on resuming a focused stride as if nothing had happened. This strategy will be least likely to inadvertently reinforce the rearing.

I’m not sure what you mean by “telling her off,” but the best advice I can give you is to ignore the rearing completely, with as little reaction as possible, and redirect by walking on with determination. Any reaction from the handler is essentially responding to the invitation to play. Verbal or physical punishment from a human is likely to represent play in horse terms.

For mares, the tendency for play behavior diminishes with maturity.

Dr. Sue McDonnell

If you effectively ignore the rearing, your mare might try alternative play initiation behavior. Some of the alternatives include a quick stamp, a head toss in your direction, pawing at your leg, nudging with her muzzle, or nipping. These are all “let’s play” gestures for horses. The trick is to keep an eye out so you can anticipate, safely avoid, and ignore the behavior. Sooner or later she should get the concept that you are not into playing. For mares, more so than with colts, the tendency for play behavior diminishes with maturity. So if you can avoid reinforcing the behavior now, hopefully the play behavior directed at you will subside as she matures.

Concerning the aggression toward other horses and the food aggression, these two are likely related to one another and probably represent a separate problem from the rearing. The best advice I know for eliminating food aggression around other horses is to have the offender on free-choice pasture with no supplemental feed and with horses that get no supplemental feed when with the offender. The more palatable the supplement and the less free-choice access, the more intense the aggression tends to be. So grains are the worst feed you can offer these horses, but even hay can stimulate serious food guarding and food aggression in some. 

About the Author

Sue McDonnell, PhD, Certified AAB

Sue M. McDonnell, PhD, is a certified applied animal behaviorist and the founding head of the equine behavior program at the University of Pennsylvania's School of Veterinary Medicine. She is also the author of numerous books and articles about horse behavior and management.

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