Understanding Your Moody Mare or Grumpy Gelding Behaviour!
Understanding Your Mare
Those of us who own a mare know that you definitely ASK a mare! Unlike geldings, mare are “entire” like stallions, meaning their reproductive system is intact and they feel the effect of their hormones throughout the seasons. Understanding your mare’s cycle and how best to support her through the seasonal changes can mean a much more harmonious relationship.
Mare’s typically cycle from spring through to autumn, although with recent changes to weather patterns and milder winters, this cycle can be longer and more erratic. The normal mare cycle (once established in the main breeding season) is 21 days. This comprises of 4 or 5 days of oestrus where she is sexually receptive and there may be increased “flirting” or mating behaviours (such as squatting, squirting or “winking”) during this time. After that she enters dioestrus where they are not receptive and may become more aggressive or dominant during that period.
Consider also whether your mare may be the Alpha Mare and how that can impact her behaviour during breeding season. In herd settings, so-called “alpha mares” often sit higher within the social hierarchy and may display more assertive or dominant behaviour, particularly during seasonal cycling. While this is frequently interpreted as temperament, research into equine social structure suggests that rank, reproductive status and resource control are closely linked, meaning hormonal fluctuation can temporarily intensify behaviours already associated with a higher social status (Houpt & Wolski, 1980; Giles et al., 2015).
Typical Behavioural Signs During Mare Seasons
Hormonal imbalance in mares often presents as inconsistency rather than dramatic behaviour. Signs commonly observed during seasonal cycling include:
- Increased vocalisation or squealing
- Tail swishing or ear pinning without clear provocation
- Frequent urination, squatting or “winking”
- Heightened distraction around other horses
There are other signs that can come with hormonal behaviour but if you are seeing any of the following signs in your mare WITHOUT hormonal signs, it is worth speaking with your vet and ruling out other sources of pain or discomfort as reasons for their behaviour.
- Noticeable mood swings or irritability
- Sensitivity when groomed around the flanks or abdomen
- Resistance to leg aids
- Variable performance from one week to the next
- Increased tension or sharpness under saddle
These behaviours can often intensify during the spring transition before settling into a more predictable rhythm.
Geldings and Seasonal Sensitivity
Although geldings do not cycle, they are not hormonally neutral. Seasonal changes in daylight affect all horses, influencing melatonin rhythms and behavioural energy levels. Increased exposure to cycling mares, shifts in social structure and rising work demands can all influence behaviour in sensitive geldings.
In many cases, these changes reflect endocrine responsiveness to stress and environment rather than reproductive hormones themselves. The same foundations that support mares through spring (metabolic stability, digestive consistency and nervous system support) often benefit hormonally reactive or “grumpy” geldings as well.
Why Spring Amplifies It and What It Really Means for Your Horse
We spend the winter slogging through mud and rain, wishing for longer days and warmer temperatures! Then spring arrives and daylight stretches into the evening, grass sugars begin to rise, training intensity increases and suddenly the same horse feels different.
A previously rideable mare becomes reactive. A cooperative gelding feels distracted. Behaviour fluctuates in ways that are difficult to explain and easy to dismiss as “just hormones”. But hormonal imbalance in mares (and hormonally influenced behaviour in geldings) is rarely that simple. Metabolism, stress physiology, body condition and digestive stability all play a role. Spring doesn’t create the problems we see and feel; it simply magnifies the horse’s underlying sensitivity.
Understanding that distinction is key to managing seasonal change well.
The Biology Behind Spring Hormonal Change
Mares are seasonally polyoestrous animals, meaning their reproductive cycles are governed by light exposure. As daylight increases, melatonin production decreases, signalling the reproductive axis to transition from winter anoestrus into active cycling ready for the breeding season ahead. This is an important observation as artificial lighting can trigger your mares reproductive system into cycling out of season. Light therapy is routinely used in the breeding industry to have mares cycling earlier – so be aware of lighting use in your stables and try to give adequate periods of darkness through the off season to help avoid your mares seasons starting up!
The spring transition phase is often irregular and before a mare settles into a consistent ovulatory rhythm, ovarian activity can fluctuate. Oestrogen levels rise and fall unpredictably. Some cycles are prolonged, others shortened. During this recalibration phase, behavioural expression can become more noticeable because hormonal signalling is inconsistent rather than stable. This is a normal physiological process but one that can feel disruptive and at times difficult to deal with in particularly sensitive individuals.
Why Some Mares Feel It More Than Others
Not all mares struggle during spring. Some move quietly through the transition whilst others experience marked behavioural change that can impact on handling and riding/trainability.
Research into equine reproductive physiology shows that metabolic status plays a significant role in how reproductive hormones are expressed (Vik et al 2006). Mares carrying excess body condition or experiencing reduced insulin sensitivity may show altered cyclicity and heightened hormonal signalling. For ridden horses this can manifest in difficult behaviours or inconsistency in training/competition.
Spring grass introduces higher sugar intake at precisely the time reproductive activity increases. If metabolic foundations are already under strain then their behavioural responses may be amplified.
Inflammatory load also matters. Excess adipose tissue (specialised fat tissue that stores energy but also acts as a hormonally active tissue influencing metabolism, inflammation and reproductive signalling) contributes to low-grade inflammation, which may lower tolerance thresholds. In this context, hormonal fluctuation is not acting alone, it is layered on top of physical sensitivity and discomfort.
This is often where targeted nutritional support for normal metabolic, hormone, muscle and gut function becomes relevant.
Hormones, Stress and Emotional Resilience
The reproductive system and the stress axis are tightly linked. Hormones involved in cycling share regulatory pathways with those governing the stress response.
Spring brings more than just daylight change, it brings increased workload, travel, competition, altered turnout and shifting herd dynamics. Research into equine social behaviour has shown that when hierarchy stability changes, tension increases - particularly in groups containing cycling mares (Stachurska et al. 2021).
Stress amplifies hormonal expression. This is why some mares feel manageable at home yet markedly different in competition environments during certain phases of their cycle. It is not simply about oestrogen levels but how well the horse is coping internally that influences how they manage trigger stacking in stressful situations.
The Gut–Hormone–Metabolism Connection
Hormonal balance is closely linked to digestive health. The delicate hindgut microbiome plays a role in nutrient absorption, inflammatory regulation and neurological signalling. Rapid forage changes, increased grass intake or inconsistent fibre supply can destabilise this system at the same time hormonal activity is increasing and placing added pressure on your horse’s systems.
When digestive stability is compromised, behavioural expression often becomes more volatile. Aiding gut function with diverse fibre sources and maintaining consistent forage first feeding routines creates a steadier physiological environment in which hormonal fluctuation is better supported.
Supporting Hormonal Balance Without Suppression - Supplements for Mares in Season
Hormonal support is not about stopping a mare cycling, it is about helping the body regulate itself more smoothly.
Certain botanicals have a long history of traditional use in supporting normal pituitary function and hormonal signalling in mares. Chaste berry for mares (known as Agnus Castus), for example, is commonly included in nutritional strategies aimed at contributing to normal hormonal balance without suppressing natural cycles. A single herb is rarely the answer though, by combining this with adequate magnesium, B-vitamins and digestive support it can act as a natural calmer and aid anti-inflammatory pathways in the bodies when cycles are in full flow. This broad nutritional approach focuses on supporting the coping mechanisms and capacity, particularly during periods of heightened stress and demand on the nervous system.
The Bigger Picture
Spring does not cause hormonal imbalance, it simply reveals how well the whole system is coping. When body condition is appropriate, blood glucose is stable, stress is managed and nutritional foundations are sound, mares often transition through seasonal change with far greater consistency. Geldings benefit from the same holistic approach.
Hormonal fluctuation is natural but by supporting balance from the inside, behaviour on the outside often becomes more predictable - not because the cycle has been altered, but because the horse feels better equipped to handle the challenges it brings. Supporting endocrine balance with appropriate minerals, B-vitamins and traditionally used botanicals such as chaste berry can contribute to steadier behaviour and improved consistency during seasonal transitions.
Because sometimes the difference between “moody mare”, “grumpy gelding” and “manageable” isn’t discipline, it’s internal balance. If you’d like to explore how targeted nutritional support can fit into your horse’s routine this spring, you can learn more here.
References:
1. Vick, M. M., Sessions, D. R., Murphy, B. A., Kennedy, E. L., Reedy, S. E., & Fitzgerald, B. P. (2006). Obesity is associated with altered metabolic and reproductive activity in the mare: effects of metformin on insulin sensitivity and reproductive cyclicity. Reproduction Fertility and Development, 18(6), 609-617.
2. Stachurska, A., Wiśniewska, A., Kuździerski, W., Różańska-Boczula, M. and Janczarek, I., 2021. Behavioural and physiological changes in a herd of Arabian mares after the separation of individuals differently ranked within the dominance hierarchy. Animals, 11(9), 2694.
3. Houpt, K.A. and Wolski, T.R., 1980. Stability of equine hierarchies and the prevention of dominance related aggression. Equine Veterinary Journal, 12(1), pp.15–18.
4. Giles, S.L., Nicol, C.J., Harris, P.A. and Rands, S.A., 2015. Dominance rank is associated with body condition in outdoor-living domestic horses (Equus caballus). Applied Animal Behaviour Science, 166, pp.71–79.
