Just like us, the horse has five senses, these are:
- Taste (gustatory)
- Smell (olfaction)
- Sight (vision)
- Hearing (auditory)
- Touch (tactile)
Being prey animals, horses need to be acutely aware of their surroundings. When we domesticate horses, these senses are still hypersensitive, and we will often deem a horse to be misbehaving by spooking or acting oddly, whereas it is more often than not their natural instincts kicking in and they are actually sensing something we aren’t even aware of! So let’s look at each sense in detail:
Taste and Smell
These senses go hand in hand as they are neurologically linked. Horses use their sense of smell to investigate objects, and they have a specialized nasal structure to do this.
When a horse meets a new object or goes to a new place they often
- Snort loudly
- Take a long breath in
The snort clears the nasal cavity of any lingering smells which might confuse the smell, and then the long inhale allows the horse to take in and process as much of the new smell as possible. Then what happens with the new smell?
- Odour particles (smells) bind to Olfactory receptor cells in the nasal cavity
- Information is relayed to the brain through Olfactory Sensory Neurones
- The brain processes the information.
The horse has a nostril on each side of its head, so it is capable of smelling two things at once, and the longer the head, the longer the nasal cavity, the more information the horse is able to process. How often have you seen a horse, when smelling an unusual or new object, throw it’s head in the air and stick up its top lip? This is the called the Flehmen response; it draws as much of the new smell as possible into its nasal cavity so that it can identify the new object.
So what is Taste? Taste is the interaction of chemical stimuli with chemoreceptors on the horse’s tongue; when a horse eats or drinks:
- The chemical stimuli (tastes) bind to Chemoreceptors (taste buds) on the tongue
- This information is relayed to the brain through Gustatory Sensory Neurones
- The brain processes the information.
Horses have been shown in research to be selective in their feed stuffs; when a horse comes across a feed stuff that has previously made them poorly they will choose to avoid this food in future. Horses will also use their sense of taste to be selective in the nutrient balance of their diet; so a horse who is deficient in salt will seek out salty feed stuffs where possible.
Let’s have a quick recap of the equine eye anatomy:
- The transparent outer layer on the eyeball – light passes through this to reach the lens.
- The coloured part of the eye, it can increase or decrease its diameter in order to control the amount of light entering the eye through …
- The black area in the middle of the Iris.
- Focuses light onto the Retina.
- Contains millions of light sensitive cells called Rods and Cones, which collect visual information.
- Optic Nerve
- Conducts the visual information received on the Retina to the brain.
Contrary to common belief, horses can see in colour. They possess a type of vision known as Dichromatic vision. In Dichromatic vision, only the three primary colours are perceived. Research has been carried out in horses to see if they are able to tell one colour from another, and a particular study by Macuda and Timney in 1999 showed that horses are able to tell red and blue from grey, but not yellow or green.
Horses eyes are on the sides of their faces, this gives them
- Wide peripheral vision
- Long distance vision
Allowing them to watch out for oncoming predators. Did you know the horse’s eye is the largest of any land mammal? They have nearly 350 degrees of vision!! However, having eyes on the sides of their head, also gives them a blind spot, which extends about 2 meters directly in front of the horse. In order to see in this space, the horse has to turn its head and use one eye only to view this area.
Horses use two different types of vision:
- Monocular vision
- Binocular vision
When a horse is stood with its head held high and is looking across a wide landscape, it uses Monocular vision, using each eye separately to view the complete landscape. Blinkers disrupt Monocular vision. The horse uses Binocular vision to use both eyes to view the same area of a surrounding, namely the path in front of it. When the horse is wearing a pair of blinkers, it is forced to use Binocular vision at all times. A horse would most commonly use Binocular vision when navigating across uneven terrain and working out the safest foot placement; and for locating the best areas of grazing. However, as we have already mentioned, the presence of the blind spot directly in front of the horse, means that it must regularly lift its nose in order to see. This blind spot is important to remember when we are jumping our horses, if a horse is allowed to approach a jump with its head up, it can see the jump as it approaches, however if ridden in an outline, they are not able to see the jump until the last second.
Horses use their hearing for three main functions
- Detect sounds
- Determine the location of sound
- Source the identity of the sound
Each ear is funnel shaped, and called a Pinnae. Each pinnae is controlled by 16 independent muscles, meaning they can move in unison or independently. The equine ear can move around a lateral arc of 180 degrees, and can respond to sounds from up to 4400m away. The anatomy of the equine ear is very complex on the inside:
- External ear
- a) The Pinna (ear flap) and annular cartilage forms the funnel shape, which concentrates incoming sound waves onto the eardrum.
- Middle ear
- a) The air filled chamber behind the ear drum, contains the malleus, incus and stapes bones which amplify sound vibrations on the eardrum towards the inner ear
- Inner ear
- a) Contains the cochlea where auditory sensitive cells are located. The auditory sensitive cells convert the sound waves into electrical impulses which are then transmitted to the brain for interpretation.
The horse interprets sound waves according to their amplitude and frequency, but not all sound is interpreted as noise by the horse, some low frequency noises are picked up as vibrations though the whiskers (vibrissae) on the muzzle and through the hooves as these two structures contain fast adapting Mechanoreceptors.
Horses in the wild use their sense of touch to form bonds with its fellow herd mates and relax. The horse’s sense of touch is highly acute, and they are able to feel far more than humans. So if you are having to kick your horse, he can feel you, he is just ignoring you!
There are a number of different receptor cells in the horses skin which are used to create the sense of touch.
- Temperature is detected by cells known as Thermoreceptors
- Pain by cells called Nociceptors
- Pressure by cells known as Mechanoreceptors.
When horses groom each other, they are using their mutual sense of touch to calm and relax each other, and create bonds between individual horses. Research has shown that horses have a lower heart rate and a higher occurrence of positive behaviours when they are carrying out mutual grooming.
A very important part of the horse’s anatomy with regards to its sense of touch, is the long hairs around the eyes and muzzle. These are known as Vibrissae and are a key component of how the horse understands its environment. They have a rich nerve supply and the horse uses them to judge distances between objects, and they are involved in the location of vibration and sound.
Therefore, the horse’s senses are far more complex than meets the eye. The way we act when around our horses will strongly influence how they perceive us, so always consider this when getting ready to see your horse today!
Written by the incredibly talented Clare Carter check her out here