Tic Toc Body Clocks

Calm and unruffled on the surface…

I love reading – if I’m not with the horses, I can usually be found with my nose tucked into a book, although sadly I do have to work from time to time to pay for my horse and book collecting habits! Apart from books featuring horses, I also enjoy reading historical fiction: much more interesting than school history, and you can learn just as much as from a dry history lesson.

On one of my groaning bookshelves at home, there’s a sub-genre of historical fiction that can broadly be summarised as “Girl or young woman finds herself in a convent. She is unhappy about this, but eventually manages to escape. Before or just after the escape, she meets the young man of her dreams. They live happily ever after, content in having informed me about 15th century Italian social customs or the dissolution of the monasteries in 16th century England!”

Clever authors make sure that as we read these stories, we are immediately able to empathise with the heroine’s situation, and we can recognize how strange and artificial it is to completely segregate a young woman from a normal mixed society. It’s usually also quite clear that this process of segregation has little effect on abolishing or even suppressing her desire to find that young man of her dreams, since she’s devoting a lot of time either thinking about him or working out how to escape her convent so that she can meet him.

Hopefully by now you’ll also have at the back of your minds a beautiful green field surrounded by high hedges, with sun shining and birds singing, and a group of beautiful mares grazing with an outward semblance of peace and contentment. But where are the males? Not a stallion, or even a gelding, to be seen! Do you know any mares who live in a convent? Are they going about their routine daily activities looking serene and relaxed – despite being a surging, roiling mass of sex hormones just under the surface?

Last week I wrote about the difference between sex roles and sexual behaviour: you might not see any active sexual behaviour from your gelding, but he will still take on the male roles in a group of horses. A mare, because she’s a mature female horse, will show both female horse sex roles and female sexual behaviours. We tend to think of females (of most species!) as passive recipients of sexual interest from males, but different sex hormones in females are responsible for both active and passive sexual behaviours. “Passive” sexual behaviours in female horses basically involve not running away from or kicking a stallion in the chest when he wants to mount her. The more subtle behaviours we often don’t notice are “active” sexual behaviours that mares show (and that stallions notice!).

To spot these, we have to think about clocks. All animals have a special set of interconnected “clocks” in their brains. These clocks help them to know what time of the day it is as well as what time of the year it is. In females, they also control whether they’re interested in a male or not (the oestrous cycle). The clocks that tell the mare that it’s spring are closely connected to the clocks that tell her “start looking for a mate!”, and they do this by releasing hormones in reponse to increasing day lengths.

We don’t really register these behaviours, any more than we do when looking at the lovely serene picture of the nuns at prayer – because they don’t appear at first glance to be sexual behaviours. But we do notice that mares start to behave in a different way when the days start to get longer. They can be distracted, more impatient, their moods can be unpredictable. While these changes happen in a natural gradual sense in feral horses, there are also some key differences with our domestically managed mares. First of all, once a feral mare is sexually mature, her brain controls a cycle that’s about 12 months long, not 21 days as we assume. That’s because adult mares aren’t intended by nature to have repeated seasons all summer: their brain aims for them to have one fertile season, followed by 11 months of pregnancy and birth followed by a fertile season. So her mood will naturally be less variable.

When a stallion isn’t around, the mare will continue to be fertile for a few days in a 21 day cycle all spring and summer. When a cycle is repeated frequently, with lots of other things happening at the same time (new horses, various life stresses, changes of feed, changes of housing), there’s more chances of it being affected by outside factors. These factors can disrupt hormone levels and affect both fertility and behaviour.

That’s why domestically managed mares can become “mareish” – they can have problems simply because they have repeated cycles when nature (and their own body) wants them to have one or two fertile seasons followed by pregnancy and birth. The more seasons they have without a pregnancy (and in fact, without access to any male horses), the more chance there is that they will have seasons that we consider problematic.

Just like the reluctant fictional nuns, a group of mares without any male horses around still need someone to take on the male sex roles (in horses, these include acting as the sentry, dealing with threats and newcomers and sometimes moving the whole group away from something. Humans understand that while taking on a role that isn’t natural for you is possible, it isn’t always comfortable and can cause you to feel unsettled or stressed. It’s the same for mares. In mixed herds where mares and geldings live together, a gelding or one of the mares will take the male sex roles (guarding and herding) in the absence of a stallion. What geldings (and mares) normally can’t do is show male sexual behaviour, in terms of courting and covering in-season mares. There are situations where mares can show male sexual behaviour but this isn’t normal (unless you’re a jenny donkey, when surprisingly enough, it is!).

Mares soon learn that while a gelding in their group looks and smells very like a stallion, he doesn’t respond to their active sexual behaviour the way a stallion would. Once they’ve tried a few times, they tend to leave him alone, although every spring when their seasons restart, they may ask again, just in case anything’s changed! Since active mare sexual behaviour involves searching for a stallion rather than waiting and hoping, they will check out every new gelding they meet. Adding a new gelding to a herd may well bring a mare into season unexpectedly. Mares kept in single sex herds may also try to escape rather more frequently than those kept in mixed herds, and many an unexpected foal has resulted from mares actively seeking out stallions, rather than from escaped stallions finding mares. The drive of sex hormones is a strong one that will often override the mare’s desire to stay with her group and her field full of grass.

Something worth bearing in mind is that stress hormones affect both the internal clocks in our bodies as well as the hormones that control sexual behaviour. Stress for a mare can be anything from the way she’s housed, the work she does as well as new companions and changes in management. Don’t forget that a mare’s hormones respond to a gradual increase in day length, but that we often stable mares inside in artificial lighting conditions throughout the winter and then turn them out once spring comes, so instead of a gradual change, they experience a sudden change in hours of light, housing, feed and companions. No wonder their first seasons of the year can be noticeable!

What then is the key to a contented mare? First and foremost, it’s likely to be a mare living in a small family group with a familiar stallion. If she can’t, because of our management, have this arrangement the next best thing is to try to ensure that she can live in a settled mixed group, so that male horses can take on the male group roles. Ideally, the mare needs familiar company: if she’s in a place where new mares and geldings arrive and leave fairly frequently, she will be more unsettled, and this will have a negative effect on her regular seasons during spring and summer.

Mares who are difficult to handle when in season can often be much easier if managed in a more natural way. For example, removing them from busy livery yards and allowing them time to settle with a smaller mixed group can often have a remarkable effect on their behaviour.

The picture at the top of this post is Shannon, a beautiful mare I used to share. When I first met her, she was living on her own and it took me a while to realise that the rides she preferred were the ones that took us to visit her previous gelding companion. After I’d been sharing her for a while, her owner moved her to a mixed group, and she became more settled. Even so, every spring she liked the rides that took us to the top of big hills, where she’d stand scenting the breeze and scanning the horizon. I’m not sure what the stallion of her dreams looked like, but I’m pretty sure she was actively looking for him. I haven’t seen her in a while, but I like to think she’s thrown off her black and white habit and escaped the convent!

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