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Horses and Their Sense of Smell

Horses Rely on Their Five Senses

A human being’s brain is designed to help us function using among other things, our fine motor skills, and our use of language.

Most of a horse’s brain is used for processing and analyzing information it picks up from its surroundings through its senses and its gross motor skills. These skills are important for a newborn horse who is designed to run within an hour after it is born. This is necessary for a horse’s survival, since horses are prey animals.

People rely on their vision and their auditory senses to gather information around them and to understand their environment. Horses rely on their five senses and especially on their sense of smell. It is thought that the horse’s sense of smell is thousands of times more powerful and sensitive than that of a person.

A Horse's Sense of Smell is Important for Socializing

Horses smell each other as a way to identify their friends.

Horses smell each other as a way to identify their friends.

Horses are Prey Animals

A horse understands the world differently than people do. People have learned to survive using language, and tools they have created. People are predators and the development since evolutionary times of human beings became geared towards the hunter and gatherers we are.

Horses, being prey animals, have learned to use their body language and their senses to survive in a world that poses dangers to them. Their only defense is to detect the predators and threats early enough so they can flee to safety. They are around scents every moment of everyday of their existence.

Their sense of smell is close to their brain, making them very reactive to smells, which gives them an opportunity to be alert to friend and foe, and that which is different, which might put them on alert.

A person’s sense of smell is closely linked to the part of brain, the lymbic system, which has to do with our emotions and memory.

Through their sense of smell, horses relate to their immediate surroundings.

Horses use their sense of smell as a recognition tool. As prey animals, horses depend on all of their senses to protect themselves from predators. The large nostrils of the horse is designed to flare to gather more smells. They pick up scents around them acutely to find food, to smell predators, to lead themselves back home through their own scents of trails, to find mates, to socialize.

Horses Sniffing Each Other

Horses go nose to nose to smell each other

Horses go nose to nose to smell each other

Horses Interpret Their World Through Their Sense of Smell

A horse’s sense of smell can help them distinguish friends, recognize mating opportunities, and smell enemies and potential danger.

Equines have a well developed sense of smell. If a horse smells moldy or stale feed, it will refuse to eat. If water smells different or the bucket the water is in smells odd to the horse, the horse won’t drink even if they are thirsty. They will drink out of a muddy puddle, because the water smells natural to them.

Horses use their sense of smell to identify predators, people, other horses, and smells in and around their environment. Horses can smell medication in their food even if it is masked in other treats.

Horses interpret much of their world through their sense of smell. Through their sense of smell they socialize, seek sexual relationships, identify territory, find food, and alert themselves of impending danger. Scent is so important to horses that orphan foals are rubbed with the sweat or manure of their newly adopted mares to be accepted. If a horse’s sense of smell is interfered with, the horse might get confused. Foals who for example, have their nostrils rubbed with Vick’s VapoRub will go to the wrong mare. Horses are also sensitive to the smell of fear in other animals and in people.

Horses Are Social Animals

How a Horse's Sense of Smell Works

Horses get a mental perception of their surroundings through their senses and this affects their behaviors.

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According to David Whitaker, PhD, from Middle Tennessee State University, horses rely on their sense of smell, the way people rely on language.

Horses stand side by side and take deep breaths to recognize each other through their smells. Horses will greet each other by going nose to nose and sniffing each other.

There is a lot we don’t understand about a horse’s sense of smell. Here are some facts we do know:

  • horses flare their nostrils to take in more scents
  • the horse’s olfactory receptors are located in the upper portion of the nasal cavity
  • Horses have two olfactory systems. The second set also known as Jacobson’s organs is the vomeronasal organs (VNO) . Many mammals, but not humans have VNO. VNO have a separate pathway to the brain and function as a completely separate sensory organ than the main olfactory system. The main purpose of the VNOs is the detection and examination of pheromones that come from other horses. The pheromones indicate an animal’s sexual status and help stallions know when a mare is in heat and open to mating and to know when a rival stallion may give him competition.

Horses like to use their sense of smell. They will outstretch their neck and point their nose towards the objects they want to sniff.

Horses have Two Different Systems to Help Them Smell

A mare can pick out her foal in a large herd by the way it smells.

Horses go nose to nose to greet each other and recognize each other through smell and sight. Through their sense of smell, horses determine which plant is tasty for them.

A horse’s sense of smell is processed in its nostrils which have a large moist surface area. The scent particles are carried through the air and picked up by the moist tissues. This information is carried to the brain, where it will be decoded. When an odor intrigues a horse, the horse will curl back their top lip and raise its head. This allows the horse to use its Jacobson’s organ more effectively. Jacobson’s organ is located towards the top of the horse’s nasal passages. The horse may look like it is laughing. This smelling posture is called the flehmen.

Jacobson’s organs are located in the mouth, under the horse’s nasal cavity. They are tubular, organs made of soft tissue, measuring about 12 centimeters long. They are lined with mucous membranes that have sensory fibers of the olfactory nerve. When a horse gets a whiff of a strong odor, the VNO expands and contracts like a pump and sends the aroma on a pathway to the brain.

Horses use their sense of smell to warn them of dangers like predators, or storms that are approaching, fires, and soiled crops. A horse’s sense of smell is also used as a social tool. Stallions also mark everywhere they go by the smell of their feces and urine.

If you have ever seen a horse curl their upper lip and tilt their head up as if they are laughing, the horse is actually doing this to help trap pheromone scents in their VNOs. This is called flehmen which means testing. It works like this; a horse draws in the smell and they curl their lip to hold the particles inside their nasal passages. Tilting their head upward helps the molecules linger in the VNOs to stimulate this olfactory system. A stallion might repeat this several times an hour if they are around a mare who is in heat. This behavior is not unique to horses. Horses will also curl their upper lip when they encounter an unusual or pungent odor. There is much that is not understood about horse pheromones, but science does know that it has an influence on a horse’s behavior.

Horses exhibit the flehmen response, which when roughly translated means testing is done to trap scents the horse smells, and analyzes the odors more closely. A horse will tilt their head up and curl their lips. They curl their lips to temporarily close their nasal passages so the horse can trap the particles. It is believed the horse tilts their head upward to help the airborne particles linger in their secondary olfactory system where the VNOs are located.

Amazing Facts About Horses

Horses Look Like They Are Laughing

Flehman response is how a horse uses their sense of smell

Flehman response is how a horse uses their sense of smell

Flehman Response

Stallions, more than any other horse show the flehmen response because it assists in identifying pheromones for mating. This happens often after a stallion has sniffed a mare’s urine or when they can smell a nearby mare in estrus.

According to Sharon Crowell-Davis, DVM, PhD of the University of Georgia, there is a connection between the flehmen response and the visual cues a horse see. When a stallion had their vision blocked they had a had a lower frequency of the flehmen response. When a horse was able to see a mare urinate, their flehmen response was higher. According to Crowell-Davis, the smell sensory was more primed with visual cues.

She believes that exposure to urine is vital for normal physical and sexual maturation in colts.

Crowell-Davis found that colts, in the first three months of being born, (young males, who are not fixed) showed the flehmen response more often than fillies. This allows the colts to get used to different smells, and learn to interpret them. Colts exhibit the flehmen response up to five times as often as fillies. Fillies show the flehmen response more often than mature mares.

Mares use flehmen when they have just given birth. It is the smell of the birthing fluids from their newborn foal that triggers the flehmen response.

Geldings, which are castrated horses, seem to use the flehmen response the least of any horse.

Although the smell of pheromones are the most likely trigger of the flehmen response, horses will also use it when they come across a strange or pungent odor.

When some odors trigger the VNOs the horse will react in certain physiological and behavioral ways.

Horses use their olfactory system every moment. There are many different odors and smells in their environment that a horse must sort out.

Mares Identify Their Young by Smell

A Sense of Smell Helps Horses Protect Themselves from Predators

A horse can identify their owner from 250 feet away, just by their smell.

Horses can’t see what is happening directly below their nose. Their sense of smell helps them know what is going on all around them.

Neurologically, smell and taste are linked together in the horse, just as they are in many other animals. Odors are important for a horse’s recognition.

All of the horse’s senses are designed to protect them from predators, and threats in their environment, since they are prey animals. A horse’s acute sense of smell has helped them survive millions of years. Their sense of smell, which is far superior to humans is an integral influence in the way they function and in their behavior. Understanding the whys and ways a horse behaves, the more we understand how to relate to these beautiful, elegant, and powerful creatures.

Horses use their Sense of Smell to Protect Themselves

Horses use their sense of smell to help

Horses use their sense of smell to help

Flehman Response in a Horse

Read the Series About Horses and Their Five Senses

Horses and Their Sense of Taste

Horses and Their Sense of Hearing

Horses and Their Sense of Vision

Horses and Their Sense of Touch

Horses and Their Ability to Communicate and Their 5 Senses


toknowinfo (author) on October 25, 2014:

Hi Alicia, Thanks for stopping by and commenting. I am glad you liked my hub. Horses are amazing animals and the more you learn about them, the more interesting they are.

Linda Crampton from British Columbia, Canada on October 25, 2014:

This is a very informative hub. I love the photos, too. They're beautiful!

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