DUN is a "dilution" gene (like Creme, Champagne, Pearl, and Silver Dapples) which modifies (dilutes - think "bleach") but does not fundamentally change the base color.

Dun is a simple dominant, meaning that the color effect is the same whether the individual has one or two Dun genes. Unlike the other dilutions which tend to dilute the entire horse, dun leaves a distinctive pattern, allowing the base coat to show through in a specific pattern that includes a dorsal stripe, horizontal "zebra" stripes on upper legs, shoulder bars, ear tips, cob-webbing on chest and face, and shaded face, just as though the horse were spray-painted with a stencil.

Red dun mustang from the Maverick-Medicine Herd Management Area in Nevada

Dun Markings: 
Any individual horse may have most, but not necessarily all of these traits:

  • diluted body color, somewhat like that of the Creme gene (this one is a MUST-HAVE)

  • dorsal stripe (this one is a MUST-HAVE)

  • "zebra" stripes on knees and hocks

  • ear lining and tips: top one-third of the ear on its back side darker than body color

  • fawn color inside of ears

  • mane and tail lined with lighter color (2-color mane & tail)

  • cob-webbing on face and/or chest

  • face darker than body color 

  • Dappling is not associated with the Dun gene (although many owners of duns report that their horses are dappled!)

Here's how Dun affects the various Base Colors:


Red Dun
left: "Max," a Sulphur mustang
Right: A bay dun mustang from the Maverick-Medicine HMA in Nevada
Bay Dun, aka Classic Dun or "Zebra Dun"
"Grullo or Grulla"

Calico Mountains grullo yearling

Grullo mustang in Colorado

Matt Fournier on Steens Vaquero

Grullo mustang in Oregon

Black Dun aka "Grullo" ("Grulla" if female)
Other modifiers, such as "Sooty" as well as variations in local soil and forage chemistry, may also be present to create a unique soft "mouse grey"  "hot chocolate," or "olive" color. The darkest grullos are called "Lobo" duns, and the lightest are called "Silver Grullos."

Granite Range HMA buckskin duns at Palomino Valley BLM Corrals 

Lark, Granite Range HMA mustang adopted by Dave & Ginny Freeman of CA

Also called "Linebacked Palominos"

Palomino Duns owned by Becky Delaney Seibel

Other Dun Terms & Variations

"Claybank Dun"

This is a common term, but there does not seem to be agreement as to what it is. I've read everything from "The palest form of red dun" to "like a very pale buckskin dun with points that are not quite black" to simply "also called red dun" Termsd like this have hostorical roots, but now that we have a better understanding of genetics, I find that such terms simply add confusion (not to mention a note of snobbery, since many people won't know what youare talking about). I prefer to use simple, clear terms that describe the underlying genetics.

Any other color or color combination can also have Dun.

Yes, Pintos can be Dun, too!

Crow (left) and Lewis (right), dun pinto South Steens HMA mustangs

Dun and Silver Dapples
Silver dun owned by Tori Seavey

Tinkerbelle, a silver dapple dun horse rescued by LipizzanLady

Sulphur Springs mustangs at an adoption

There are certain Wild Horse Herd Management Areas within the American West - most notably the Sulphur Springs in southwestern Utah, Kiger/Riddle in Oregon, the Pryor Mountains in Montana, and the Carter Reservoir herd in California/Nevada - that are known for their many dun colored horses. Horses from these areas are not exclusively dun, but well-marked duns occur in significant numbers in these herds, along with the bays, blacks and reds that make up the base colors.

Duns also occur in most wild herds.

Kiger horses on the range

Carter Reservoir mustangs (photo courtesy of Jona Kalayjian)


NO. Dun (along with bay, black, red, roan, the pinto/paint patterns, gray and appaloosa spotting patterns) came to America with the Spanish Conquistadores in the 1500's. Although a wild horse with dun will usually have some "Old Spanish" ancestry (most wild horses do), the presence of dun coloring does not make the horse "primitive" or more "Old Spanish" than any another horse.

Dun is valued for its exotic appearance, and, in both Mustangs and Quarter Horses, it is indicative of at least some Old Spanish lineage. (While some modern non-Spanish horses, such as the Fjord, are also dun, these are not known to have contributed to mustang gene pools)

Grullos from the Calico Mtns HMA. Like most Mustangs of Southeastern Oregon, Northwestern Nevada, and Northeastern California, the Calico Mountains horses' DNA tests show a close relationship to South American horses of known Spanish ancestry and to the "gaited North American Saddle breeds".

Dun's association with being "primitive" or "ancient" is likely because some very old breeds of horses, such as Mongolian horses and the very ancient Przewalski's Horse, and some old breeds of European Draft horses, are duns. There is also the matter of the Portuguese Sorraia, which, in terms of its possible contribution to American Mustang populations, is unlikely, although the theory has some strong proponents.

Bottom line is - Dun is a color. There is nothing primitive about today's modern dun-colored horses.

Rhonda Groves and Oregon (non-Kiger) dun mustang, "Latte"

Divide Basin (Wyoming) HMA

Andi Harmon's Lobo Dun (dark grulla, black drugs) mare, "Star"

Grullo Stud Horse from Twin Peaks HMA on BLM Internet Adoption

Gus, day adopted by Sherry Timm - note yellowish baby coat

Two years later, Gus in full Grullo coloring

Grullo Overo gelding at National Wild Horse & Burro Show, Reno, NV, June 2001

Soft Coffee-Cream Grulla mare and foal at Palomino Valley
Black-based Grullo foals often start out yellowish, and darken as they mature.

This yellow-ish colt shed out to full-fledged Grullo.

Some horses appear to have a dorsal stripe, but it either disappears upon maturity, or with seasonal shedding.  This coloring is called called "counter-shading", a function of the "Sooty" gene, and it can be confusing to horse owners. See this link for more: Sooty Foals and Countershading

Bays commonly have a "line-back" which, although it appears to be a true dorsal stripe, is not Dun.

Dun is a term often used to mean buckskin, and vice versa. For some breed registry associations that is a correct usage. For mustangs, the term Dun refers to horses with dun factor markings only. Here is a great website about this issue: BUCKSKIN vs DUN

Spirit, Stallion of the Cimarron

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