When you disturb your horse’s sense of smell, like overwhelming it with a very strong scent, her social interactions are radically altered.
As prey animals, horses need to be able to detect even the slightest scent of danger on the wind to stay safe. Horses are also quick to note the smell of fear in other animals and humans.
Because horses have such a radically different landscape of scents than we ourselves do, studying their sense of smell is difficult. Partly because we can’t appreciate all the complications that can occur during research and partly because we don’t understand all the intricacies.
Just like we can’t ask a blind person to describe the hues of different colours, we can’t appreciate the catalogue of scents that a horse registers.
“Horses depend on their sense of smell the way we depend on language.”
– David Whitaker, PhD
Horses have a much better sense of smell than we do
If you’ve ever ridden a horse on the trail only to have her stop and drop her head to sniff the ground intently, it’s because she’s smelling the other animals (most often horses) that have been on the trail.
Your horse’s long head means that she has a large, long nasal cavity and her flexible nostrils get considerably bigger as she flares them to investigate a scent she’s curious about.
The large nasal cavity is very effective for decoding smells. The odour particles from the air are inhaled by the horse and deposited onto the moist tissues of the nostrils.
Inside her nasal cavity are structures called turbinate bones that cause the inhaled air to stir around.
This warms the air as well as distributes the scents over the receptors in the top part of the nasal cavity. The horse’s nasal cavity is large and has many scent receptors.
From there the information is sent on to the brain for processing.
If a horse is suddenly spooked by seemingly nothing, it might have been caused by a smell undetected by humans.
It’s even suspected that your horse’s famous ability to find her way home from unfamiliar territory is largely accomplished by her retracing her steps, by sniffing out her footprints and finding her own manure “markers” along the trail she used when moving away from home.
Smelling things keeps your horse safe
A herd of horses can be leisurely grazing in a field when suddenly one of them flings up her head suddenly. Nostrils flaring, she’s instantly on full alert, although her eyes can’t perceive any visible threats.
The faint scent of a potential predator has registered and soon the whole herd is on the move, getting as far away from the scent as they can.
This daily scenario, and many more, tells you that your horse receives a lot of critical information about her world through the sense of smell.
We have paltry olfactory abilities and can hardly appreciate the amazing sensitivity and range of smells that horse’s experience.
Horses use smells to identify relatives and friends, distinguish between herd members, seek sexual relationships, recognise territories, find food and water as well as sense danger.
Like most predators, we rely on our vision a lot, whereas horses reply far more on chemical messages in the air than their less accurate vision.
Your horse may object to a certain smell and react to it with fear
This is usually connected to a prior negative experience.
Knowing to stay away from where the wind carries the smell of smoke towards you helps horses in the wild run away from forest fires.
Your horse can also be fearful of a smell that she experienced at the same time as she experienced something unpleasant.
For instance, if you once wore a perfume while the vet was giving your horse a vaccination, she may now react nervously or run away from you every time you wear that perfume.
Your horse may also hesitate when passing a certain spot on a trail that has been marked by another animal or a human. She may stop to sniff the area deeply and become very nervous.
Many people say that their horses know when they come into the territory of a bear or other predatory animal.
This primal sense keeps them safe in the wild and their instincts will kick in even when you know that there isn’t anything dangerous around.
Your horse can’t vomit and it’s her sense of smell and taste that protects her from eating and drinking anything harmful
When food and drink pass over the tongue of your horse it’s accepted or rejected before your horse swallows it.
This is important because your horse is extremely sensitive to moulds and other things that cause an imbalance in the gastrointestinal tract.
Your horse won’t generally eat food that has mould in it or drink what that is off. However, her sense of self-preservation will only work as long as she has better quality food and water to choose from.
If she’s hungry and hasn’t been fed, or if she isn’t fed often enough, she’ll eat just about anything in order to abolish her hunger or satisfy her innate need to constantly graze.
An orphaned foal, or a horse that was raised by humans as an orphan, may eat plants that are harmful because she didn’t get the opportunity to learn which plants to choose by watching her dam eat.
Your horse recognises harmful and medicinal plants by their smell, if she learned from her mother which plants should be avoided.
The safest thing to do is to always remove harmful plants from the reach of your horse and make sure that your horse is fed enough food and given enough forage.
Your horse can detect subtle differences in the mineral content of water and can sometimes refuse to drink unfamiliar water
This can happen, for instance, when you’re travelling with your horse.
Knowing that your horse naturally likes salty tastes and will learn to like sweet ones can be a good thing to know (many horse owners can attest to their horse’s love of peppermint candies).
If you’re trying to water your horse in an unfamiliar place, where you know the water is good, but your horse refuses to drink it, you can use flavours, such as apple juice, to help disguise the taste of the water.
Any changes in your horse’s diet always need to be gradual, so adding apple juice to the water will need to happen incrementally over the course of a few weeks.
The same will then need to be done once your horse is drinking the water and you want to start decreasing the amount of apple juice. If you abruptly stop adding the flavour to the water, your horse may go back to refusing to drink it.
It’s also believed that horses recognise the scent of food and water. They can detect the scent of supplements or medications hidden in their food that to us, seems to have no scent or is masked by other scents.
Scent is critical for foals and mares
When a foal is born, the mare will devotedly lick her newborn dry. As she does so, she breathes deeply of her baby’s scent and memorises it. She may even flehmen to mark the scent more strongly in her memory.
After this first imprinting of the scent, the mare will be able to pick her foal out of a group of other horses. This is critical once they rejoin the herd after birth.
Identifying individuals by smell is so crucial to mares that foster dams can be encouraged to adopt a foal that isn’t her own by rubbing the foal down with the mare’s manure or with the smell of her sweat (or even draped in the skin of her own foal that died, but the other two methods are much faster and easier to accomplish).
Getting a mare to adopt a foal can also be achieved by temporarily disturbing the function of the mare’s sense of smell. Foals whose nostrils have been coated with something pungent, like Vick’s VapoRub, have difficulty recognising their dams and will often go to the wrong mare.
Handlers can sometimes use this technique deliberately when horses that are unfamiliar to each other are forced into close proximity, such as in a shipping van.
Reportedly a mixture of one part each of natural rosewood oil, cumin and anise can help, though I doubt this has been clinically tested.
A strong-smelling substance smeared on the nostrils will temporarily cut down on squabbles.
Your horse uses scent to get a first impression
When your horse was introduced to her pasture mates for the first time, she probably trotted optimistically towards them and stopped just a short distance away from the herd.
Out of the herd stepped the first brave soul, most likely the highest ranking horse, with the neck arched and the ears flicking back and forth, to meet your horse nostril to nostril.
Both breathed deeply of the other’s scent and after a long moment of snuffling the muzzles, they both shifted to sniff each other’s flanks and finally underneath the tail.
A few stamps and squeals may be ensue from this contact and once the introductions have been made, the other members come closer to inspect the newcomer.
When your horse meets other horses for the first time, you’ll see her touch noses with the other horse or snort softly before maybe exchanging squeals and kicks to determine who’s where in the pecking order.
Horses usually like to smell the manure of other horses, and a herd of horses can poop in order of rank in one pile – the higher ranking ones depositing their scent on top of the lower-ranking members to establish superiority.
There was a study done in 2011 that showed some evidence that horses can recognise the manure of other horses. In the study, horses seemed to pay most attention to the manure of horses that had been aggressive towards them.
Your horse may check out new people by giving them a good sniff (and picking their pockets if they know that’s where you usually keep candies)
It’s hard to say what your horse is identifying when smelling people. Since a priority for horses is determining if you’re dangerous that’s probably one motivation.
She’s also most likely seeing what she can find out about you (do you smell like other animals) and do you have something she can eat (another priority for horses).
There has been some study into horses’ ability to detect human emotions and Dr Antonio Lanatá with his colleagues at the University of Pisa in Italy, have found that horses can smell fear and happiness.
According to Dr Lanatá, when your horse is introduced to a new person she will smell that person to try and detect who they are feeling – this will tell your horse how to react to that person, in turn.
Other than that she may be earmarking your scent in case you come back again and she needs to decide if that’s a good or a bad thing from her perspective.
Your horse’s nose never rests
She constantly analyses smells throughout the day – in the barn, out in the stabling yard, on the trail, in the field, in the stall – to decode things about her environment.
She’s constantly processing the smells of humans, dogs and cats, herd members, water smells, plant smells and any smells she comes across in the environment to find out who’s passed through.
In a stable or domestic setting, your horse’s sense of smell can be overwhelmed by artificial odours that emanate from things like liniments, fly sprays, deworming drugs and even the deodorant or perfume you wear.
Depending on how prevalent these smells are they can significantly alter your horse’s sense of smell and change the emphasis on her senses. This can, in turn, influence her behaviour both with people and other horses.
Wild horses probably have a keener sense of smell that hasn’t been regularly assaulted by an incredibly rich landscape of smells. They have fewer scents to catalogue and work with than domesticated horses.
Your horse’s sense of smell is a marvel
She can identify you by your smell at a 100 paces and smell the yucky medicines you tried to hide in her feed (even when you mix in generous helpings of molasses and applesauce, which in themselves are a clue).
Your horse can’t compete with a bloodhound, but if you take a wrong turn in the woods she’ll find her way home even without a trail to follow.
