Mares Behaving Badly: Is it Estrus or Something Else?

Mares Behaving Badly: Is it Estrus or Something Else?

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Is it estrus or something else?

Rides on Ruby haven’t been much fun lately. She swishes her tail, screams to horses near and far, refuses to respond to cues, and just has a generally unpredictable attitude.

It’s not unusual for mares to exhibit behavior changes related to their estrous cycles. Sometimes the behavior interferes with their management, training, or performance, which can be frustrating for owners, handlers, and riders. It’s no surprise, then, that when a mare is particularly moody or distracted, we blame her demeanor and actions on estrus. In some instances, however, the unwanted behavior stems from some other problem entirely. Figuring out the root of the behavior is the first step in trying to address it in a positive way.

Normal vs. Abnormal Behavior  

Mares are seasonal breeders that cycle from about early May through October. A normal cycle consists of roughly seven days of estrus and a 14-day period of diestrus (when she is not in heat). 

“The behavior of a mare in diestrus (which involves active rejection of the stallion) generally is not objectionable for training or riding her,” says Ryan Ferris, DVM, MS, Dipl. ACT, an assistant professor at Colorado State University’s (CSU) Equine Reproduction Laboratory, in Fort Collins. “During the seven-day period of estrus, the mare may show an undesirable attitude—squealing at other horses, urinating small amounts frequently, (becoming) easily distracted by other horses (she’s in the arena, but clearly her mind isn’t), etc.” These are all normal behaviors associated with estrus.

“Mares generally do not cycle year-round,” he continues. “Often mare owners/riders are quite happy with their mares’ behavior in late fall, winter, and early spring. The ovaries become smaller and inactive, and these mares don’t show signs of estrus during that time.”

While this is normal behavior, it can be challenging if the mare’s in training or showing.

Continue reading this article in the March 2017 issue of The Horse: Your Guide To Equine Health Care to learn about health problems that can mimic signs of estrus and ways to prevent estrus behavior. Subscribe now and get an immediate download of this issue.

About the Author

Heather Smith Thomas

Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog,, she writes a biweekly blog at that comes out on Tuesdays.

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