Have you ever taken a close look at a horse and wondered, “What exactly are those hard growths on his legs?” Or have strange little spots on his coat made you pause for a second? Unusual features like these have many a horse owner and animal enthusiast scratching their heads. Turns out, horses are full of little anatomical mysteries. Here’s what we know about things like ergots and chestnuts on horses.
What are chestnuts on horses?
The hard calluses on the inside of each leg are called chestnuts. You’ll find them just above the knee on the inside of the front legs and just below the hocks on the inside of the hind legs. Their texture is reminiscent of human fingernails (and hooves).
Chestnuts are remnants of equine evolution. Thousands of years ago, horses had multiple toes, which evolved into a single, long toe—or hoof—to help increase their speed to escape predators.
One theory suggests that chestnuts, sometimes called “night eyes,” once helped horses see in the dark. However, in modern horses, chestnuts no longer serve a specific purpose.
Made of keratin, chestnuts continue to grow throughout a horse’s life, much like human fingernails. So if you notice them flaking or peeling off, that’s perfectly normal. While the outer surface has no nerve endings—meaning horses don’t feel anything when you touch the chestnut—they can sense where the chestnut is attached to the skin.
Are ergots the same as chestnuts?
Ergots are hard calluses, much like chestnuts, but they are located on the back underside of the fetlock (ankle) joint. They are not as noticeable as chestnuts. In fact, most horses’ ergots are no larger than a pencil eraser.
Similar to chestnuts, ergots are believed to be vestiges of the modern horse’s multi-toed ancestors—likely related to a toe or a dewclaw. They also continue to grow like human fingernails, with some horses developing longer ergots than others. These little calluses do not have nerve endings on their outer layer, but the horse does feel where the ergot is connected at the skin.
Why does my solid-colored horse have small white spots on his coat?
Seemingly random small white spots can appear spontaneously on a horse’s coat, though no one knows exactly why. Fortunately, they’re harmless and typically don’t indicate a skin injury. These white spots are known as “Birdcatcher spots,” named after a 19th-century Thoroughbred that had the unusual markings on his flanks. These spots have been found to run in certain equine families, pointing to a possible genetic cause.
Why is there a dip above my horse’s eyes?
The “dip” above the horse’s eye is the supraorbital fossa. It is a depression in the skull that contains fat and muscle tissue. Sometimes, it can provide clues about a horse’s body condition. If the dip (or “dent” as some might call it) is deep, the horse might be in poor condition. If the dip is shallow or nonexistent, then the horse might be in good condition or even overweight.
Take-Home Message
These are just a few of the quirky features you might find on your horse—things that simply make them more fascinating! From evolutionary remains to unusual markings, they give horses a unique touch.
Related Reading: A Comprehensive Guide to Common Horse Coat Colors
Megan Arszman, a lifelong horsewoman, loves sharing her passion for horses with others, especially her daughter. Together, they enjoy riding their Quarter Horses around their Central Indiana farm and spend weekends showing Miniature Horses and dogs.
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