What causes the black stripe down the back of dun horses?


Dun horses are known for their unique appearance, which includes a dark stripe running down their back. This black stripe is often referred to as the dorsal stripe and can range in color from dark brown to almost black. But what causes this distinctive marking? The answer lies in the horse’s genetics, environment, and primitive history.

Genetics behind dun horses

Understanding the genetics behind dun horses can help to unravel the mystery of the black stripe. Dun is a coat color that is controlled by a single gene. This dominant gene is responsible for the dilution of the base color of the horse’s coat. This dilution results in a lighter-colored coat with darker points, mane, and tail.

Understanding the dun gene

The dun gene affects the pigment distribution in the horse’s hair, resulting in a diluted color. However, it also causes other distinctive markings, such as the dorsal stripe, leg barring, and shoulder stripes. These markings are known as primitive markings and are thought to be a remnant of the wild ancestor of horses.

The role of agouti gene

Another gene that plays a role in the dun horse’s appearance is the agouti gene. This gene determines the distribution of black pigment in the horse’s coat. The agouti gene affects the dorsal stripe’s color, making it darker. When the agouti gene is absent or recessive, the dorsal stripe may appear more brown than black.

The influence of environment

While genetics play a significant role in the appearance of dun horses, environmental factors can also affect their coat color. Sun exposure, nutrition, and stress can all impact the intensity of the dorsal stripe. In some cases, a horse’s stripe may fade or darken over time depending on these factors.

The connection to primitive markings

As mentioned earlier, the dorsal stripe is one of several primitive markings that are often found on dun horses. These markings are believed to be evolutionary remnants of the horse’s wild ancestor. The dorsal stripe, in particular, may have provided camouflage against predators or helped to dissipate heat.

The significance of dorsal stripe

In addition to its primitive origins, the dorsal stripe also has cultural significance. In some Native American tribes, the black stripe is believed to represent a horse’s connection to the spiritual realm. The stripe is seen as a symbol of power, agility, and freedom.

The link to ancient horse breeds

Dun horses have been around for thousands of years, and their distinctive markings have been documented in ancient artwork and texts. Some breeds, such as the Icelandic horse and the Mustang, are known for their dun coat colors and primitive markings. These breeds are thought to be descendants of the wild horses that roamed the earth thousands of years ago.

The mystery of dun horses solved?

While the genetics behind dun horses and their distinctive markings are well understood, there is still much to learn about these fascinating animals. Ongoing research may shed more light on the evolutionary origins of the dorsal stripe and the other primitive markings found on dun horses.


In conclusion, the black stripe down the back of dun horses is a result of genetics, environmental factors, and primitive history. The unique appearance of dun horses and their markings have captivated horse enthusiasts for centuries. Today, they continue to be admired for their beauty and their connection to the wild horses that once roamed the earth.

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