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I went to see my neighbors’ new horse. He told me he bought a blue dun, but the horse I saw looked almost solid black. I wasn’t sure he was right about his horses’ coloring, so I decided to research dun horses.
Dun horse’s unique color pattern is created by a modifier gene that affects both black- and red-base coat colors. This gene lightens their coat but doesn’t affect the horse’s primitive markings. Classic dun horses have tan coats with darker points and a dark crisp stripe down the center of their back.
Duns come in various coat colors, and some blue duns are so dark they almost look black. Many people favor dun horses for their unique coloring, but there’s a lot more to duns than an alluring color pattern.
What determines if a horse is a dun?
Duns have a distinct color pattern caused by genetic influence of a horses base coat. We’ll get into more detail about the genetics but first there are some important basics to cover about dun horses.
All Dun horses have a clean crisp dorsal stripe
A classic dun horse has a yellow or tan coat with dark points and primitive markings. Primitive markings include dorsal stripes, horizontal zebra stripings on the upper legs, and sometimes a stripe across the withers.
Many Dun horses have visible primitive markings, but all dun horses have a dorsal stripe, running from the poll to the dock of the tail. Hence, the name line-backed dun.
Coloring and markings vary in intensity and depth in dun horses, but their clean, crisp dorsal stripe is constant, and most have dark-tipped ears. Distinguishing a dun is often tricky because countershading, sooting, or other color modifications mimic dun coloring.
The most common dun color pattern looks very similar to buckskin.
The most common colored dun horse is the classic dun, which looks similar to a buckskin horse. However, duns have characteristics that make them unique.
To learn more about the differences between duns and buckskin horses you should read this article: Dun vs. Buckskin Horses, What’s the Difference? 5 Clues.
Differentiating dun factors from non-dun factors in foals is especially tricky. Frequently foals are born with primitive markings that disappear after their foal coat sheds.
In gray foals, the presence of primitive markings is frequent. The foal markings often lead owners to misidentify a gray foal as a dun.
Countershading is often mistaken for Dun traits
Countershading is a color pattern describing an animal’s back that is dark while its underside is light. This type of shading blends animals in with their surroundings and looks similar to dun markings.
Countershading can be distinguished from dun because the dark areas are not typically as clean and crisp and often fades during the summer months.
Some dun horses have unique markings
Dorsal Stripe
A dorsal stripe is a clean, crisp mark that runs through a horses mane to the dock of its tail. It is permanent and is the color of the horses’ base coat color. A dorsal stripe on a bay horse, however, can be either black or reddish.
Leg markings
Most duns have horizontal striping on the back of their forelegs; however, the markings are often faint. These markings are sometimes called zebra bars, and most commonly appear above the knees and hocks.
Face mask
Dun horses typically have a dark area around the front of the face and their forehead. Cobwebbing, or spiderwebbing, is subtle stripes on the forehead.
Shoulder stripe
The shoulder stripe runs crosswise from the center of the back down either side of the withers, it is perpendicular to the dorsal line. Think of the shoulder stripe commonly seen in donkeys.
Dun Frosting
The hairs on either side of the mane and both sides of the dock of the tail may be significantly light-colored, creating a semblance of frosting. On some horses, frosting is very pronounced, but it can also be subtle.
Ear Tips
Dark marks the same color as the dorsal stripe on the back of the horses’ ears. The marks may involve only the rim, the rear of the ear tip, or a distinct strip below the tip.
The genetics of the dun horse color pattern.
A dilution gene causes a horse’s base coat to become lighter, without affecting the primitive markings and points (Points are the extremities of a horse, their mane, tail, lower legs, and ear tips.).
Although the most common result is the classic dun, there are many variations and different colored dun horses.
All horses have either a base of chestnut or black. They are distinguished genetically by the presence or absence of the extension gene “e.” “EE” is black, and “ee” is used to reference chestnut.
All horse color coats are created by modification genes acting on these two bases.
Dun is a dominant gene “D”
The dun gene is represented as “D” and dilutes both red and black color coats. The colors that result from the dilution range from apricot, golden, dark gray, olive, and many other subtle variations.
Dun is a dominant gene, it always shows, and every dun horse must have at least one parent with the gene. Through genetic testing, you can determine if your foal is a dun. U.C. Davis labs provide genetic testing for horses.
The dun gene is prevalent in many horse breeds but is more common in heavy pony types such as fjord horse, Icelandic horse, highland pony, and the Shetland pony.
Duns are rare in Thoroughbreds and breeds with a lot of Arabian influence. Duns are not often seen in the heavy draft breeds.
A red dun has a chestnut base color
Red Dun. In the photo is a dark red dun; however, red duns can be as light as the color of a peach. All duns have a dark dorsal stripe, and commonly have leg bars and cob webbing.
Red duns are created by the dun dilution gene working on the chestnut base coat. Red duns are easy to misidentify because the contrast between the markings and the coat is not as apparent as is in other colors. A red dun with a flaxen main and tail is called a claybank dun.
Blue duns have a black base color
There’s a wide variety of names used to describe a grulla dun; people refer to them as blue duns, black duns, grey duns, and mouse duns. But, regardless of what they’re called, these horses have the dun gene “D,” diluting the “EE” black base coat.
The dilution creates a smoky blue color that ranges from light silver or light mouse grey to a deep dark grey that looks almost black. The horses’ mane, tail, points, and primitive markings remain the base color of black.
Dun horses don’t turn gray
Dun horses do not get lighter as they age and do not have an intermingling of white and dark hairs. Dun is a term used to describe a particular genetic makeup of a horse.
Some dun horses will display gray coloring, such as a blue dun, but it is a dun horse, not a gray. For a horse to be characterized as a “gray,” the horse must have a single dominant allele gene.
A gray foal can be born any color, and as it matures, white hairs begin to replace birth colored hairs. As the horse continues to age, the number of white hair increases to exhibit classic gray features.
Often gray foals are challenging to distinguish from a dun because some exhibit dun features before they mature. Duns don’t change color.
Bay dun is the most common color of duns.
A bay dun is the most common dun coloring. It is considered the classic dun and sometimes referred to as a yellow dun. The coat color ranges from creamy yellow to deep reddish gold. It is often confused with a buckskin.
A buckskin with a dorsal stripe is a dun.
Buckskin horses and bay duns are challenging to distinguish. They both have similar coat colors and dark points derived from a bay base. Duns get their characteristics from a dun dilution gene, while buckskins characteristics are from a cream dilution gene.
Describing the differences in genes doesn’t help when looking at the horses; however, genetically, they can be tested to ensure their offspring’s coloring.
The visual test to determine if you have a buckskin or a dun is to check for a clear and distinct dorsal stripe present in all dun horses. If no distinct dorsal line, then the horse is a buckskin.
Is Spirit a dun or buckskin?
Buckskins with a dorsal stripe are duns, but some people call them buckskin duns or “dunskins.” Spirit is a dun but also qualifies as a dunskin or buckskin dun.
Claybank duns are rare.
A claybank dun is a red dun with a flaxen mane and tail. And yes, this is a rare dun color. The most common dun is a bay dun. The claybank horse has amber eyes and hooves that are lightly-pigmented.
Within the grulla duns, the dark blue dun is considered rare. But I don’t know how rare they can be since I know of a couple of dark blue duns living near me. These dun horses are so dark they look black.
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