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The Seasonal Mare ~ Could our management make them worse?

seasonal mares in the sea

Mares are a bit like marmite, especially chestnut mares. Most people either always look for a mare, or try to avoid them. This is essentially because unlike geldings, mares still have all their hormones, which can take over control of their behaviour, making them more difficult to handle. While those hormones will always be there, I recently learnt that how we manage the seasonal mare can actually make the behaviour worse.

An overview of the seasonal mare

When we talk about a seasonal mare, we typically mean a mare who shows annoying, difficult behaviour at certain times. Each mare is different and can show different behaviours at different times. But understanding the biology of what is going on can help a little bit.

Mares are polyoestrus, this means that they ovulate multiple times throughout the year. However, most mares don’t ovulate over the winter months. This is because the foal would be born in the middle of winter, which is higher risk. Over the winter mares enter anoestrus, where essentially their reproductive system goes into hibernation. This is why lot’s of mares are much easier to manage over the winter as there are less hormones affecting their behaviour.

The rest of the year, typically from April to October, the mare cycles between oestrus and dioestrus. Oestrus is when the mare is displaying typical in season behaviour. There might be squatting, squirting, presenting etc. This is because she is about to ovulate and most fertile. In the wild, mares in oestrus will approach the stallion multiple times a day to mate. This typically lasts 4-7 days.

The mare then moves in dioestrus where the corpus lutiem is formed. This lasts 13-17 days in which time she will reject the stallion. Towards the end of this stage, she will either be pregnant, or the corpus lutiem will break down and she will return to oestrus. This is when the mare tends to be most aggitated, showing more aggressive or difficult behaviours such as biting, kicking out.

An insight into the mares mind

Smaller social circles

Mares tend to be pickier about their social circle. In the wild groups of mares tend to be about 2-4, 8 mares maximum. When larger groups have been found with a stallion, when the stallion leaves these groups break down into smaller groups.

This is reflected with how mares raise their foals. Studies have found that mares spend more time teaching their colt foals social skills, than their fillies. So many mares may lack the social skills to operate in larger groups. The closest bond for a mare is her mate, followed by her foal, then any young offspring of hers. A small number of mares she likes is last.

Failure causes stress

When the mare can’t achieve their goal, this increases their stress levels, which can increase the behaviour we don’t want to see. When she is cycling, her goal is to get pregnant. In wild herds, failure to conceive can lead to group instability which in turn leads to aggression.

Similarly, if a mare doesn’t like her field companions, or there are too many companions, being fenced in with them can increase her stress levels.

Management Solutions for the Seasonal Mare

Obviously, having a foal out of your seasonal mare just to improve her behaviour isn’t really viable option, especially with the over population of horses in the UK currently.

But a really interesting way to think of it is, on average, we only need our horses to behave nicely for 1 hour of the day. The other 23 hours they can do whatever they want. If we can make those other 23 hours as relaxing as possible for them, when we ask more of them in that one hour, their stress levels should be low enough that it shouldn’t be a problem.

There are 4 building blocks to this method; nutrition, environment, physical and behaviour.


We all know now that what our horses eat can have a huge impact on their behaviour. They should have a high fibre diet and ideally have access to forage 24/7. They should be fed hard feed for the work they are doing. I am a huge fan of balancers for making sure a horse is getting everything they need without having to feed lots of hard feed.

There is also an interesting new supplement about to hit the shelves aimed at hormonal mares. Keep your eyes peeled!


Many yards keep mares and geldings separate. But that might not actually be the problem. Some mares prefer the company of geldings and it is herd size what is the problem for them. Mares typically prefer pairs or small group turn out. If this isn’t possible, is the field big enough for smaller groups to break off from each other?

Are they stabled over night? Do they get on with their neighbours? Even though they aren’t in contact with their neighbours, being so close to them can cause stress if they don’t like them. Is it possible to move to a stable next to a horse they like?


Are you sure any undesirable behaviour is hormonal and not pain related? It’s always worth giving them a thorough MOT if you are having problems with their behaviour just to rule out another cause.


If your actions seem to cause some of the undesirable behaviours, you can train them to not react. For example, a horse who reacts badly to grooming, instead of sticking with it when they are kicking off, build it up slowly where you can. Stop brushing them before they react badly, so that they are rewarded for tolerating the brushing. You should then be able to build up how long you can brush them for without getting bad reactions.

Using these four building blocks to give your mare a more positive mindset will mean that she is less likely to show the negative behaviours what are often escalated by stress. There could be less field injuries, a tidier stable and less aggressive behaviours. Yes some of the solutions can be tricky at the start, but they could massively help you and your mare in the long run.

Last Updated on 17/02/2021

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