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Few animals on Earth can beat the horse in terms of elegance and grace. Humans have always found horses a pleasure to look upon, with their long legs, slender necks, and expressive movement.
However, all things we find so mesmerizing about the horse’s appearance play an important role in the survival of the species.
The anatomy of horses has perfectly adapted to living on grasslands and running away from predators.
As a result, they have many unique and eccentric features that set them apart from most other animals.
In this article, we bring you some of the most intriguing horse anatomy facts so you can marvel some more at these amazing creatures!
Think you’re an expert in horse anatomy? Test your knowledge with our fun horse anatomy quiz!
Horses Can Sleep Standing Up
Thanks to an anatomical structure called the stay apparatus, horses are able to sleep standing up. The stay apparatus consists of a series of ligaments and tendons that allow the horse to lock their stifle and hock in place.
As a result, horses are able to doze off standing on three legs while their fourth leg is resting. The stay apparatus is also the reason why horses can’t move their stifle and hock separately.
Being able to sleep standing up is a useful survival tactic as it allows the horse to quickly run away from predators. However, they still need to lie down for deep (RAM) sleep to complete their sleeping cycle.
Horses Have The Biggest Eyes of All Terrestrial Mammals
Being a prey animal means horses must have an excellent visual range to be able to detect danger in their environment. As a result, evolution has given horses extremely large eyes compared to other land mammals.
In comparison to the human eye, for example, horses’ eyes are eight times larger in size! This allows them to see almost 360 degrees around themselves, with just a small blind spot directly in front and behind.
However, this doesn’t mean that horses have better vision than us. Because their binocular range is only 55 to 65 degrees, horses have relatively poor depth perception and ability to make out details.
What their eyes are really good at is detecting motion. As a result, they are ultra-aware of all moving things in their environment. This explains why horses often spook at sudden movement, especially if it’s in their peripheral vision where they can’t make out shapes clearly.
A Horse’s Teeth Take Up More Space in Their Skull Than Their Brain
Like many other herbivores, horses are born with fully formed teeth that continuously erupt throughout their lives. When a horse is young, most of their teeth are still in their skull and take up more space than any other organ.
As horses grasp and grind up feed material, their incisors, premolars, and molars gradually wear down, which stimulates the eruption of new teeth.
Because horses chew in a circular motion, sharp points are often created at the edges of the teeth. Hence why regular dental care is an important part of maintaining a horse’s oral health.
Arabian Horses Have Fewer Bones Than The Average Horse
Horses typically have around 205 bones in total, which is only one less than we do. However, Arabian horses tend to have 201 bones on average, although not all individuals share this trait.
When looking at an Arabian horse, it’s easy to notice their short backs and high tail carriage.
These traits are the result of Arabians having one less pair of ribs (17 instead of 18) and lumbar vertebrae (5 instead of 6), as well as fewer tail vertebrae.
Horses Lack a Gallbladder
Unlike humans, horses don’t have a gallbladder and therefore cannot store bile. Bile is an emulsifying agent produced in the liver that helps break down fats.
Because horses eat frequent, small meals instead of fewer large meals like humans, they don’t need a large amount of bile released at once.
Instead of a gallbladder, horses have multiple bile ducts trickling bile into the intestines at a relatively constant rate.
Other animals that lack a gallbladder include deer, rats, some species of birds, and invertebrates.
Horses Don’t Have a Collarbone
In humans, collarbones attach the arms to the body by forming a connection between the shoulder blades and the breastbone.
Horses, on the other hand, don’t have a collarbone and therefore lack a bony connection between the forelimbs and the thorax.
However, they do have a strong group of muscles, ligaments, and tendons attaching the forelegs to the body. This group is called the thoracic sling and it serves as a replacement for a collarbone in horses.
Unlike the collarbone which is a rigid structure, the thoracic sling allows horses to extend their legs and run at high speeds.
For this reason, most four-legged runners like dogs, cats, and deer also lack a collarbone.
Related: 12 Facts About the Horse Skeleton
A Horse’s Whiskers Act As Their “Third Eye”
Due to the lateral placement of their eyes, horses have a very wide visual range of approximately 350 degrees. However, they do have a small blind spot of about 5 degrees directly in front of and behind their heads.
To prevent the horse from being caught out, nature has come up with some clever solutions for covering these blind spots.
The one behind the horse can be easily covered by the animal moving their head slightly. Whereas, the horse’s whiskers act as a “third eye” to compensate for the blind spot ahead.
These highly sensitive tactile hairs send sensory signals to the brain at a speed of 250 mph. Because they are an important part of the horse’s perception, the FEI has banned the trimming of whiskers for aesthetic purposes in equestrian competitions.
All Horses Are Naturally Asymmetrical
Most horses wear their manes on either the left or right side. This is the result of one shoulder being bigger and stronger than the other and causing the mane to fall on the opposite side.
In most cases, the stronger and more dominant shoulder is on the left side, which is why horses tend to prefer the left rein.
This natural asymmetry starts at birth, as horses are born in a diving position with one leg slightly in front of the other. The leg that comes out first will usually be the dominant one.
As riders, it is our job to strengthen the muscles on the weaker side and straighten the horse. A crooked horse will always be imbalanced on one side, which can affect both horse and rider performance.
It Takes Around a Year to Regrow an Entire Hoof
The average horse’s hooves grow at a rate of ¼ inch to ½ inch per month. Knowing that the hoof can be 2½ to 4 inches long, we can calculate that it takes about a year to grow out an entire hoof.
However, the growth rate of hooves does vary somewhat depending on season, nutrition, age, exercise, and whether the horse wears shoes.
Hooves tend to grow faster in the summer and without shoes, as contact with the ground stimulates blood flow which stimulates hoof growth.
Related: Why Do Horses Need Horseshoes?
Female Horses Have Fewer Teeth Than Males
While all horses will have at least 36 teeth at maturity, males are more likely to develop wolf teeth and can have up to 40. These usually appear at around 5 months to a year into the horse’s life.
According to veterinarian Glennon Mays, wolf teeth helped the ancestors of horses chew twigs and leaves that formed the main part of their diet. However, since modern horses live on a grass-based diet, wolf teeth have become redundant in these animals.
While male horses have a higher chance of developing wolf teeth, females can also have them occasionally.
Since these teeth often interfere with the bit, they are routinely removed in many riding horses.
Horses Cannot Breathe Through Their Mouth
Another fun horse anatomy fact is that horses are obligate nasal breathers, meaning they can only breathe through their nose.
When the horse is not swallowing, the epiglottis forms an airtight seal with the soft palate at the back of the oral cavity.
As a result, there is no way for the horse to draw air into the lungs through the mouth.
The only exception is horses suffering from a condition called the dorsal displacement of the soft palate (DDSP). In these horses, the airtight seal between the epiglottis and the soft palate is broken and air can pass from the mouth to the trachea.
Horses Carry Vestigial Toes on Their Legs
Today’s modern horses walk on a single fortified toe, the equivalent of our middle finger. This trait is what makes them such efficient runners and so light on their feet despite their large size.
However, horses didn’t always use to be this way. Their earliest known ancestor, the Eohippus, used to walk on four toes on the front legs and three toes on the back.
Over the last 55 million years, the horse gradually lost these additional toes, but they didn’t disappear completely.
The second and fourth toes are actually found on either side of the cannon bone and go by the name of splint bones.
Some scientists believe the small ripples on the end of the splints are the vestigial first and fifth toes. Others think they are completely gone.
Moreover, the small keratin deposits known as chestnuts and ergots are believed to be remnants of the horse’s carpal pads.
These pads are still visible on some of the horse’s distant relatives, such as tapirs and rhinos.
Horses Have Enormous Hearts
Not just figuratively, but literally. The average horse’s heart is about 10 times the size of a human heart and weighs 9-10 pounds (4-4.5 kg). In contrast, a human heart is only 10-12 ounces (0.28-0.34 kg) on average.
While those are already impressive numbers, the weight of a top equine athlete’s heart far exceeds the average.
Racehorses in general tend to have enlarged hearts due to the high-intensity exercise they carry out on a regular basis.
For example, the legendary racehorse Secretariat’s heart was more than double the normal size and weighed a staggering 21-22 pounds (9.5-10 kg).
Moreover, the Australian racing champion Phar Lap‘s heart was an impressive 14 pounds (6.35 kg).
The Average Horse’s Brain is About Half The Size of a Human Brain
As a general rule, brain size relative to body size reflects an animal’s intelligence and mental capacity. While horses are certainly an intelligent species, their brain size to body size ratio is considerably smaller than ours.
The average human brain weighs between 2.6 and 3 pounds (1.2-1.4 kg), or around 2% of our body weight. On the other hand, the horse’s brain typically weighs 1.3 to 1.7 pounds (0.6-0.8 kg), or 0.15% of their body weight. Its size is comparable to that of a grapefruit or a child’s brain.
While a horse’s brain might only be half as big as ours, it has certain areas that are better developed. One such area is the cerebellum, which is responsible for movement coordination and balance.
Horses have a larger cerebellum than humans, meaning their overall motor skills exceed our own.
Other well-developed areas of the equine brain include olfaction and communication via body language. However, horses lack most units associated with complex emotions, thoughts, and reasoning.
Related: How Smart are Horses?
A Horse’s Knee is The Equivalent of Our Wrist
What most people call the horse’s knee on the front legs is actually analogous to our wrist. Also known as the carpus, it is a complex joint made up of small irregular bones arranged in two rows.
Meanwhile, the horse’s true knee is located high up on the hind legs, where their abdomen meets the thighs.
When the horse moves, you can see the patella or kneecap protruding at every step.