Keeping Horses in Harems

Q. I am a veterinarian in Atlanta with a special interest in behavior. I also own and raise Arabian horses. I have a 2 1/2-year-old stallion, and I would like to keep him in a harem situation. He is now pastured with another gelding and is quite socialized to other horses. Recently, he bred a very experienced older broodmare, who did a great job "patiently educating" him.

What has research told us about stallion behavior in a "natural" husbandry situation? Will these stallions become more aggressive or difficult to handle? (I would like to use this horse as a riding horse, and he is currently very easy to handle.)

Is it possible to keep a gelding at pasture with a stallion and his harem? Also, is there any research on using Regumate to prevent pregnancy in mares long-term? I'd greatly appreciate input and ideas.

Jenny Price

A. These are great questions that I can answer from my experience. Most of what I've learned about the effects of various domestic management schemes on stallion behavior comes from doing research for other main reasons, but during which we moved stallions from one type of housing and management to another. What we inadvertently saw moved us to do some research specifically on those questions. The rest of my understanding of the topic comes from clinical experience with stallions in various farm conditions.

One of the first things to consider in keeping a stallion under "harem" conditions, either in a pasture with mares or along a fence line of a pasture with mares, is that he will almost always exhibit all the normal stallion-like behaviors. He'll herd and direct the mares when threatened, look after any young, etc. One of the practical challenges if you want to work the stallion outside the pasture is that he will likely be reluctant to leave, at least until he learns that you'll work with him, then return him, and that all will be well out there with his mares when he gets back. My experience is that most stallions with pasture breeding harems are not necessarily harder to handle for work once they figure out that you'll take them back to their mares.

If there are geldings with the group, or on a nearby fence line, that might take over the mares when the stallion is gone, there could be significant concern and struggle for the stallion to get back to his job of protecting the mares, and it will likely take him longer to learn that all will be well when he returns. Some of this will be difficult to condition.

A related challenge is how to get mares in and out peacefully for work. Many stallions will have to be confined in a safe enclosure or you'll get a lot of fight at the gate. Many will "fret the fence line" and keep the other mares herded tightly near the gate until the mare returns. Others seem to understand the drill and only fuss when you leave and return. But it can be very dangerous to fight with a harem stallion for his mares. Never take chances, because a seemingly relaxed stallion can be inadvertently stimulated into serious action. Fairly simple, inexpensive facilities that provide safe physical separation, such as a round pen, can improve safety for animals and people.

Another consideration is that most stallions going from traditional "isolation housing" to harem-like exposure to mares have increased reproductive function, with more testosterone and other reproductive hormones. So they'll be stronger, more muscled, more poised, and full of themselves. Some gelding/stallion pairs do OK in this situation, except for taking the stallion in and out. The gelding typically takes the role of a bachelor stallion, keeping his distance when the stallion harasses him away from the mares. There will often be a lot of carrying on at first, so it can be nerve-wracking. With lots of obstacle-free space to work it out, they usually settle down within a few hours with occasional flare-ups.

Taking the stallion in and out will stir things up. When he leaves, most geldings rise to the occasion and look after the mares. This can really upset the stallion. One solution is to take the gelding out first and place him away from the mares.

On birth control for mares, in my experience it takes a lot of Regumate to inhibit ovulation and breeding at pasture with a harem stallion. It would be expensive and beyond label recommendations, so it's not a reasonable strategy. I don't know of data on that, just clinical experience.

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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