07/24/2025
For years, horse owners and trainers have often blamed a mare’s misbehavior on her hormones. Kicking at the stall wall? Must be her cycle. Refusing to focus under saddle? Probably "hormonal." But groundbreaking new research from the University of California, Davis, is challenging that long-held belief — and the results may surprise you.
🧪 What They Studied:
Researchers at UC Davis examined 2,914 hormonal profiles from mares who had been referred to their Clinical Endocrinology Laboratory and Equine Reproduction Service. Each case file included concerns around behavior — words like “misbehaving,” “aggressive,” or “difficult” showed up consistently. The scientists wanted to know: Are these behavioral issues really linked to elevated ovarian hormones, like testosterone or estrogen?
📉 What They Found:
Out of all the data, less than 10% of the mares with reported misbehavior actually had elevated hormone levels. In fact, the only pattern that showed a reliable hormonal connection was a very specific kind of stallion-like behavior — things like loud vocalizations, biting, or mounting other horses. But the more common forms of acting out — such as irritability, reluctance to work, or general aggression — showed no significant connection to elevated hormone concentrations.
💡 So What Does This Mean?
It means we may need to stop assuming that hormones are the root of every behavioral quirk a mare displays. The UC Davis team emphasized that these results debunk a major misconception in the horse world — that mares act up because of their ovaries. According to the data, most misbehavior has nothing to do with hormones.
🎯 Why This Matters:
Understanding that behavior isn’t always tied to biology helps owners and veterinarians take a more holistic approach. If a mare is acting out, the cause might be pain, stress, environment, lack of enrichment, or even training confusion — not just her heat cycle. With this new insight, we can better meet our horses' needs and stop unfairly labeling mares based on assumptions.
📌 Takeaway:
Mares aren’t moody — they’re complex individuals. And sometimes, when she’s “acting up,” it’s not about her hormones at all. It's time we listened a little closer and looked a little deeper.
