How Hormones Impact Horses' Behavior

A mare joke or a brave mother?

This blog post is companion to my 9/7/23 chat with Jec Aristotle Ballou on Horse Hormones and Training
The photo above appeared on facebook with the caption that the zebra must be a mare. Such jokes at mares’ expense represent a common stereotype about mare behavior. But is that stereotype justified? Or is this a mare defending her foal from the leopard? Oxytocin, the hormone related to maternal and social bonding and trust, provides female mammals the courage to protect those they care about, particularly their off-spring. I didn’t see a joke; I saw a brave mother. Most people believe there are behavior differences between mares and geldings. Depending on the source, mares are “sensitive, loyal, and brave” OR “difficult, impatient, touchy, temperamental, and aggressive.” Geldings are described as steady, reliable, more forgiving, and less reactive. Stallions are commonly depicted as aggressive. Since LUST is a Core Emotion that controls potent hormones, we would naturally expect gender differences, but do they fit the stereotypes? The sole scientific study I found of mare / gelding behavior differences was an owner survey with 1,000+ respondents (statistically significant) who did NOT know the purpose of the study. Results: NO differences were found in the behavior of mares and geldings when ridden. On the ground only 2 statistically significant differences were noted. 1. Mares moved away more when being caught (Personal Space). 2. Geldings chewed more on leads and blankets (mouthiness). Although one study isn’t conclusive, it raises the question of where did the idea of “marish” behavior come from? One of the researchers suggested, “This might be coming from the human world. Traditionally there are stereotypes against women, that they’re moody or bossy or difficult, and it’s possible that this has just transferred onto horses as well.” Dr. Sue McDonnell has been a behaviorist at University of Pennsylvania’s New Bolton Center for decades. She reports that most mares presented to New Bolton for “hormone” problems really had problems related to the way they were handled. Incorrectly dismissing problem behaviors as gender related means real causes go unaddressed, thus compromising horse welfare and human safety. Real causes include:
1. Poor socialization and anxiety due to early weaning and lack of adult role models.
2. Lifestyles lacking essential Friends, Forage, and Freedom.
3. Poor handling and training, which creates confusion, anxiety, and defensiveness that are often escalated by negative human responses.
4. Food sensitivities
5. Natural variations in mares’ heat cycles
6. Medical problems

Sapphire used to be "stall aggressive"

Sapphire, my husband’s first mare, was described as pushy, dominant, defensive about her stall, and food aggressive. She had scared people everywhere she lived. I was advised never to lead her without a chain over her nose, and never let her get away with anything. The chain didn’t last; synchronized leading quickly improved leadline manners. But, anticipating “pushy” behavior, I was assertive, stern, and quick to correct her. I now realize I created a vicious cycle that became a self-fulfilling prophecy. I couldn’t understand why my husband never had a problem. He was much less experienced than I was, and didn’t know how to set limits “proper limits”. Yet she was polite and reliable for him. Then Brandy taught me about being a Protector Leader, focusing on helping horses feel safe instead of demanding obedience. Could it be that Sapphire’s “pushiness” was really the defensiveness of a sensitive, anxious horse? I tried handling her gently, asked quietly for what I wanted, and gave her time to comply. I never lowered my standards of behavior; I was just passively persistent instead of pushy. Her threatening, "marish" behavior disappeared, and her true personality came out; calm, gentle, and cooperative. Ironically, the first comment on my post about this topic was, “Mares are only tougher to train if you're using force.” I suspect all horses are harder to train and handle when you use force. My book is a blueprint for how to be a Protector Leader. Many readers report the same transformations with difficult horses that I experienced with Sapphire. What Horses Really Want: Unlocking the Secrets to Trust, Confidence, and Reliability is available from: Amazon , Horse and Rider Books and in Polish from Galaktyka

Is Shiloh threatening me?

The essence of managing behaviors called “marish” is being a Protector Leader, who helps your horse feel safe instead of a dominant leader focused on obedience. This starts with responding to the emotion behind the behavior. What is your horse telling you? What is the behavior meant to accomplish? Looking only at Shiloh's hind leg, one might think she is threatening to kick me. In fact, she is lifting her leg so I can reach to clean her udder which is dirty and itchy. Notice the relaxed head position and facial expression, and extended upper lip. When Shiloh first tried to tell me her udder bothered her, she lifted a hind leg as I groomed her, and I scolded her for lifting her leg. I was slow to catch on that she was trying to show me the body part that needed attention! There are more details in my articles about being a Protector Leader

Mares with difficult heats Mares can feel discomfort or pain during estrus, something women should be particularly sympathetic about instead of making jokes. Some mare owners develop their own "TLC Protocol" for those days, limiting activities and expectations to whatever the mare is comfortable with, such such as easier rides or ground work or hand walks, or just a gentle massage. Addressing training, handling, and possible food sensitivities can lower stress and make some mares more comfortable. If a mare still is uncomfortable, you can talk with your vet about herbs, drugs, or a Pearl Pod IUD. A mare who acts like a stallion, such as mounting other mares, may have been on anabolic steroids or have a type of ovarian tumor.

Geldings acting like stallions This can happen when castration has not been fully susccessful (cryptorchid), when food sensitivities trigger unwanted behavior, and (apparently more likely in teenage geldings) when there is a tumor on the pituitary gland. Poor socialization can also lead to unwanted behaviors. Bronzz, the sweet fellow holding the food dish in the next photo, has been my wonderfully reliable partner for 25 years. However, he grew up as many horses do, with no adult male role models to show him how to behave. He is so quick to fight with other geldings that I will never again risk pasturing him with a gelding.

Food can seriously impact a horse's behavior

Food sensitivities are more common that generally realized and they can impact behavior very quickly. Legumes (clover, soy, alfalfa or lucerne) are high in phytoestrogens, compounds found in plants that function similarly to estrogen. Phytoestrogens are especially high in soy, a common ingredient in horse feed. Behavior changes documented in other species include aggression and excitability. Owners report similar impacts on horses, and have found that a diet change can create a huge change in behavior. More details in this article. Can Food make My Horse Behave Badly?

Dartmoor Stallion Shilstone Rocks Snowshoes

Stallions have an undeserved reputation for aggression. In a natural herd, the stallion is the primary sentinel and protector. He also plays with youngsters, supervises them, and herds them back to the band when they wander too far. Peaceful stallions have more loyal mares, and more, healthier off-spring. Drama does not create a healthy environment in which to raise the young. The aggression often seen in domestic stallions is a result of their being poorly socialized, poorly trained, isolated (a significant mental health issue in any social species), and treated aggressively. "Shoes" is a high level competition driving pony, pictured above in a large class of mixed genders at the Walnut Hill Driving Competition, one of the largest in the country. He lives with mares and foals, providing the youngsters with a well-socialized male role model. This is especially important for the healthy social development of colts.

References:
Study: Mares Not “More Difficult” Than Geldings by Christa Lesté-Lasserre, MA
The researchers don’t know why mares often have a “bad reputation” and get stereotyped as being “bossy” or “difficult,” but the origins might be in anthropomorphism, said Fenner. “This might be coming from the human world,” she said. “Traditionally there are stereotypes against women, that they’re moody or bossy or difficult, and it’s possible that this has just transferred onto horses as well.”
https://thehorse.com/192301/study-mares-not-more-difficult-than-geldings/
Reported Behavioural Differences between Geldings and Mares Challenge Sex-Driven Stereotypes in Ridden Equine Behaviour by Anna Aune, Kate Fenner, Bethany Wilson, Elissa Cameron, Andrew McLean, and Paul McGreevy
Geldings are more likely to chew on rugs and lead ropes when tied, and mares are more likely to move away when being caught in paddock. No differences in ridden behavior
https://www.mdpi.com/2076-2615/10/3/414
Differences Between Mares and Geldings / March 12, 2015 by Nancy Diehl, VMD, MS
Mares might also exhibit stallionlike behaviors, including herding and mounting other mares. This has been observed in mares that have been on anabolic steroids and in those with certain ovarian tumors
https://staging.thehorse.com/111581/differences-between-mares-and-geldings/
Heather Smith Thomas, “Mares Behaving Badly: Is it Estrus or Something Else?” The Horse, April 16, 2019
https://thehorse.com/19902/mares-behaving-badly-is-it-estrus-or-something-else/
Alexandra Beckstett, “Behavior Problems in Mares: Ovaries Aren’t Always to Blame”, The Horse, February 2, 2018
https://thehorse.com/139452/behavior-problems-in-mares-ovaries-arent-always-to-blame/
Abnormal Mare Behavior? Don’t Blame It On Her Hormones May 5, 2023 by Kevin VanderHorst
https://thehorse.com/1121793/abnormal-mare-behavior-dont-blame-it-on-her-hormones/
‘STUDDY’ BEHAVIOR IN GELDINGS December 24, 2020 by Katherine Houpt, DVM, PhD, DACVB, With Jennifer Von Geldern
https://horseandrider.com/horse-health-care/stallion-like-behavior-in-geldings/
Effects of Feeding on Behavior of Horses May 25, 2012 By Dr. Joe Pagan
https://ker.com/equinews/effects-feeding-behavior-horses/
The pros and cons of phytoestrogens By Heather B. Patisaul and Wendy Jefferson
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3074428/
Increased aggressive behavior and decreased affiliative behavior in adult male monkeys after long-term consumption of diets rich in soy protein and isoflavones by Neal G Simon et al.
https://www.sciencedirect.com/science/article/abs/pii/S0018506X04000169
Soy Safety: Depends on the Source, Nutritionists Say By Lisa Kemp | Oct 27, 2008
https://thehorse.com/123469/soy-safety-depends-on-the-source-nutritionists-say/
Protein Punch: Soybeans in Horse Feeds September 25, 2015 By Kentucky Equine Research Staff
https://ker.com/equinews/protein-punch-soybeans-horse-feeds/
GMO and Glyphosates: What You Need to Know for Your Horse’s Health By Joyce Harman, DVM -November 2, 2019
https://www.horseillustrated.com/gmo-and-glyphosates https://harmanyequine.com/gmo-and-glyphosates/
Lucerne Hay in Equine Diets April 15, 2011 By Dr. Peter Huntington
https://ker.com/equinews/lucerne-hay-in-equine-diets1/?highlight=clover
Myths and Truths About Alfalfa Posted on March 1, 2021 by Dr. Kellon
https://drkhorsesense.wordpress.com/2021/03/01/myths-and-truths-about-alfalfa/
All About Feeding Horses Alfalfa By Heather Smith Thomas | Mar 11, 2019
https://thehorse.com/110110/all-about-alfalfa/
Adding Fuel to the Fire: How Diet Affects Horse Behavior April 2, 2023 by Diane E. Rice
https://thehorse.com/1120993/adding-fuel-to-the-fire-how-diet-affects-horse-behavior-2/

Additional Resources
“Marish Behavior”: What Causes It? By Lynn Acton
https://www.lynnacton.com/Articles-Videos/Horse-Behavior-Herd-Dynamics/Marish-Behavior-What-Causes-it/
“Marish” Mares and Personal Space by Lynn Acton
https://www.lynnacton.com/MiniPosts/Marish-Mares-and-Personal-Space/i-6ZXBxDh