Black horses have always captivated me with their sleek, glossy coats that shimmer in the sun. From the distinguished Cavalry Blacks of the British Household Cavalry to the solemn riderless horses at state funerals, black horses naturally command attention and admiration wherever they go. But what exactly sets a black horse apart from the rest?
In this article, we’ll delve into the intriguing world of black horse coat color genetics to uncover the secrets behind their striking appearance. We’ll explore the unique characteristics that define these magnificent animals, highlight the horse breeds most renowned for their black coats, and celebrate some of the most beloved black horses throughout history.
Whether you’re a seasoned equestrian or simply captivated by these elegant creatures, there’s something here for everyone who shares a passion for black horses.
Note: we have a glossary at the end of the article defining some complex terms.
What is a Black Horse?
A black horse is characterized by a completely black coat, including its mane, tail, and lower legs. It is one of the 3 equine base colors (the other two are bay and chestnut) and can range from a sun-bleached “brownish tan” tone to pitch black with blue undertones.
Key Features of Black Horses
- Base Color: Black (E_ aa). Shades can range from fading black to pitch black. Note: black foals are usually born a slate grey color and develop their black coat with the first coat shed.
- Points: Mane, tail, and lower legs are black, unless modified by markings or white patterns.
- Eyes: Typically dark brown, hazel, or black; occasionally blue or multicolored if influenced by coat pattern genes.
- Skin Pigmentation: Generally dark, though pink skin occurs under white markings.
- Markings: Black horses can have white facial or leg markings, and pattern genes like tobiano or sabino may create unique designs.
- Variations: Although they don’t vary as much as bay and chestnut coats, blacks can still vary in shade from a sun-bleached tan color to pitch black.
The Science of Black Horse Coat Color Genetics
Black horse color genetics involves a change in DNA coding at the ASIP, or Agouti, gene. This gene controls the distribution of black pigment over the horse.
In the bay horse (E_A_), a dominant copy of the gene (A) restricts it to the points. In black horses (E_aa), the gene has lost this functionality so black pigment spreads right across the entire horse.
Key Facts About Horse Black Coat Color Genetics
- Two Pigments: Horses produce two types of pigment – black (eumelanin) and red (pheomelanin). These two pigments between them create all the various equine coat colors.
- Three Base Colors: Horses have three base colors: bay, black, and red (chestnut). All other coat colors arise from these three.
- Pigment Production: By default, a horse’s melanocytes (pigment-producing cells) produce red pigment. However, certain genetic mechanisms “switch on” the production of black pigment.
- Genes Involved: The two main genes responsible for determining mammalian base color are:
- MC1R (Extension Gene, E): Controls whether black pigment (eumelanin) is produced. A dominant allele (E) enables black pigment production, while a recessive allele (e) restricts the horse to producing only red pigment (pheomelanin).
- ASIP (Agouti Gene, A): Controls the distribution of black pigment. A dominant allele (A) restricts black pigment to the horse’s “points” (mane, tail, and lower legs), while a recessive allele (a) allows black pigment to cover the entire coat.
What Makes a Black Horse Black?
For a horse to be black, it must inherit:
- At least one dominant Extension (E) allele so it can produce black pigment.
- TWO copies of the recessive Agouti (a) allele to allow unrestricted black pigment spread across the body.
Black Coat Color Pigment and Genetic “Switches”
- When the dominant Extension (E) allele is present, it produces a protein that switches ON black pigment production.
- When the dominant Agouti (A) allele is present, it produces a protein that acts as a second switch to restrict black pigment to specific areas of the coat (the mane, tail, and lower legs). Without this Agouti (A) allele, all the horse’s melanocytes produce black pigment instead to create an all-over black-pigmented coat (aa).
Why is the Black Horse Coat Color Unique?
Black horses and ponies are found in most breeds unless the color has been purposely bred out (Cleveland Bays are a good example of this). That tells us the genetic change that created it probably happened very early in the horse’s domestication, if not before. At that time, most horses were also likely still dun so the first “black” horses would have been grullas (black duns).
It’s also important to understand that black is not a ‘derivative’ of bay. It is its own unique base color, and is created by a genetic change in DNA coding that disables the mechanism that normally switches off black pigment production in equine melanocytes.
So, unlike bay horses that can produce both black and red pigment, black horses are unique in that they can only produce black pigment.
Simplified Genetics Breakdown
- Black (E_ aa): Produces only black pigment, covering the entire coat.
- Bay (E_ A_): Produces both black and red pigments, with black pigment restricted to the points.
- Chestnut (ee _ _): Produces only red pigment, with no black pigment present.
Genetics in Action
All black horses, regardless of whether they are fading or non-fading, or look more brown than black, have: at least one dominant Extension (E) allele and TWO recessive Agouti (a) alleles. Even one dominant agouti (A) allele will allow black pigment to be switched off, and make the horse genetically bay, not black.
This genetic change creates an all-over black-pigmented horse that often stands out with bluish undertones to its coat.
Black Coat Variations
Many people think black is black but, just like bays and chestnuts come in a range of coat color shades, so too do blacks. But again, it’s important to understand that factors other than genetics can also influence black coat color, including nutrition and sun bleaching. That “dark brown” horse for instance could be a black horse with a copper and/or zinc deficiency.
Both copper and zinc are important for pigment production. Zinc in particular is involved in black pigment production and a deficiency will often show up as a “sun-bleached” or faded looking coat. Excessive iron in the diet can also cause black pigment in manes and tails to turn a coppery reddish color.
The two most common black horse coat color shades are:
Non-Fading Black
Non-fading blacks tend not to fade, even in full sun and will stay a rich, jet black color all year round. However – referring back to my point about nutrition, a good balanced diet with all the essential minerals in the right amounts will help a black horse stay black.
Fading Black
Some black horses always fade at certain times of the year, regardless of nutrition. They can even look like dark bays at various times, with fading or tan coloring apparent on the flanks and around the girth. However, true blacks tend to retain a black muzzle, where dark bays will have a mealy or tan muzzle.
Black Horse Breeds
Black horses can be found in most breeds, except in cases where the color has been selectively bred out. For instance, Cleveland Bays are exclusively bay-colored.
Here is a summary of common black horse breeds:
- Friesian: probably the best-known “black horse” breed, selectively bred for its non-fading black coat color. However, chestnuts do exist in the breed, although they are not generally registrable as breeding stock.
- Mérens: hailing from the Ariège Pyrenees in Southern France, Mérens horses, or the Ariégeois pony, are always black.
- Murgese: this Italian breed is predominantly either black or blue (black) roan in color.
- Kladruber: a very old, quite rare Czech breed that is always black, or grey (we can assume the greys are also genetically black).
Black is also common in breeds like the:
- Dales Pony: an endangered British native breed, many Dales ponies are black.
- Fell Pony: another iconic native British breed that is often black.
- Shetland Pony: black is a popular color in this breed too.
If you’d like to know more about these breeds, read our black horse breeds guide.
Summary
Black horses are more than just a striking coat color -they are living embodiments of strength, grace, and history. Whether you’re admiring a Friesian’s majestic gait or uncovering the secrets of their genetics, there’s no denying the allure of these remarkable animals.
So, the next time you see a black horse shimmering in the sunlight, you’ll know there’s a fascinating science and rich heritage behind that glossy coat.
Glossary
- Agouti (ASIP) Gene: A gene that controls the distribution of black pigment in a horse’s coat. The dominant allele (A) restricts black pigment to the horse’s points (mane, tail, and lower legs), while the recessive allele (a) allows black pigment to cover the entire coat.
- Allele: A variation of a gene. Horses inherit two alleles (one from each parent) for every gene, which together determine traits like coat color.
- Base Colors: The three fundamental coat colors in horses: bay, black, and chestnut (red). All other coat colors derive from these base colors.
- Dominant Allele: A version of a gene that only needs one copy to express a trait (e.g., the “E” allele for black pigment production).
- Eumelanin: A type of pigment responsible for black or dark coloration in a horse’s coat.
- Extension (MC1R) Gene: A gene that determines whether a horse can produce black pigment. The dominant allele (E) allows for black pigment production, while the recessive allele (e) restricts the horse to producing only red pigment.
- Fading Black: A black horse coat color that lightens or takes on a tan or brownish hue, especially when exposed to sunlight or due to nutritional deficiencies.
- Non-Fading Black: A black horse coat color that remains rich and jet black year-round, regardless of sunlight exposure.
- Pheomelanin: A type of pigment responsible for red or chestnut coloration in a horse’s coat.
- Points: Specific areas of a horse’s coat (mane, tail, and lower legs) that can display a different color from the body, often black in bay and buckskin horses.
- Recessive Allele: A version of a gene that must be inherited from both parents (two copies) to express a trait (e.g., the “a” allele for a completely black coat).
- Sun Bleaching: A phenomenon where a horse’s coat fades or changes color due to prolonged exposure to sunlight, often seen in fading black horses.
- Melanocytes: Pigment-producing cells in a horse’s skin and coat. These cells produce eumelanin (black) and pheomelanin (red), which determine coat color.
- Grulla (or Grullo): A specific coat color in horses caused by a dilution gene acting on a black base coat, giving it a smoky or mouse-gray appearance.
- Tobiano: A coat pattern caused by a gene that produces large, white patches across a horse’s body, often seen in combination with black or bay base coats.
- Sabino: A genetic pattern causing irregular white markings on a horse’s coat, which may appear on black horses, creating unique designs.
FAQs
Are Black Horses Rare?
Black horses are less common than bay or chestnut horses but are not considered extremely rare. Their prevalence varies by breed, as some breeds like Friesians and Mérens are selectively bred for their black coats.
Are Black Foals Born Black?
No, black foals are often born with a slate gray or smoky brown coat. Their true black color develops after they shed their foal coat.
What is the Difference Between a Black Horse and a Dark Bay?
Dark bay horses have a brown or reddish tint to their coat, with black points (mane, tail, and legs). In contrast, a true black horse has no reddish tones and a fully black coat. The muzzle is a reliable indicator – a black horse’s muzzle is black, while a dark bay’s muzzle may appear tan or mealy.
Can Black Horses Have Blue Eyes?
It’s uncommon, but black horses can have blue or multicolored eyes if other genetic factors, like white coat patterns (e.g., overo or sabino), influence eye color.
Do Black Horses Symbolize Anything?
Black horses are often associated with power, mystery, and elegance. In some cultures and traditions, they represent strength, protection, or even spiritual guardianship.
