The Sheltie Colors: Photos, Oddities, and Genetics
Shetland Sheepdog coat colors are further defined by their patterns, such as the Irish pattern (white fur on the chest, collar, underbelly, legs, and tail tip) and the Piebald pattern, also known as white factoring.
In this article, we'll take a look at the Sheltie colors one by one, and then see how the main Sheltie color genes interact to produce these combinations.
The Pure Sable Sheltie
The Sable coat creates that classic Shetland Sheepdog look; the one that summons joyous cries of "Aww look! A mini Lassie!" When we’re talking Pure Sable, we’re talking golden, light tan, or ginger fur.
Pure Sable puppies are actually born with gray fur, which slowly intensifies to gold or tan as they mature. Here's our Sheltie puppy, Howard, at around 8 weeks old. He has with muted gray fluff on his back, with tan fur on his face and legs.
Now here's Howard in his adult coat. It's a distinctive mix of gold, tan, and ginger. We think he was probably a Pure Sable Sheltie because he lacked an abundance of black fur tips. But as you'll see in a moment, looks can be deceiving when it comes to deciphering Sheltie color genes.
The Mahogany Sable Sheltie
The Mahogany Sable Sheltie tends to develop much darker fur in the realm of chestnut or mahogany, which is tipped or heavily overlaid with black.
Also known as Shaded Sable, this Sheltie color can develop very slowly over the lifetime. For instance, at one year old, Piper was more orange than chestnut colored, and while he had a fair amount of black tips around his face, to the untrained eye he looked like a regular tan Sable.
But over the years, Piper's coat grew darker and darker until, eventually, his coat was dominated by solid black fur!
Meanwhile, Howard's intense ginger fur softened with old age. While people once struggled to tell our Sable Shelties apart, they ultimately developed very different coats, and we ended up with one tan dog and one black dog.
Howard and Piper shared a Pure Sable father. So why did they develop such different coat colors in the end? It comes down to gene interactions, based on the genetic variants introduced by their different mothers.
In a moment, we'll take a look at the Sheltie color genes that likely created these different colors. First, let's go back to our list of the main Sheltie colors.
The Tri Color Sheltie
The Tri Color Sheltie has a combination of black, white, and tan. There's an Irish pattern of white fur on the chest and legs. Tan fur appears in little splashes around the cheeks, throat, ears, eyes, legs and under the tail.
Tri Color Shelties are less common than Sables. This is because their dominant color variant is Sable, while Black is recessive. In most other dog breeds, the opposite is true. Shelties share Sable dominance with Rough Collies, Corgis, and Pomeranians.
The Blue Merle Sheltie
Look at this handsome devil. Is this Sheltie blue? Is he gray? Is he silver? Only he knows. The rest of us call him a Blue Merle, for his dominant blue-gray fur which is interspersed with a mottled pattern, known as dapple in other dog breeds, or merle in Shelties.
Genetically speaking, the Blue Merle Sheltie is essentially a Tri Color with color modifications. In other words, the merle gene dilutes what would otherwise be black fur into various shades of gray or light blue.
In conformation shows, judges deduct points for rustiness in the Blue Merle coat, as well as faded or washed-out colors. Self-color, defined as a solid block coat color without any merle pattern, and appearing simply as a faded Tri Color, is also considered a fault.
The Bi Black Sheltie
The highly unusual Bi Black Sheltie has solid black hairs which make up most of the coat color, besides the traitional Irish pattern. This distinctive two-color combo is so-named because bi is Latin for two, and black is the dominant color.
In breed shows, solid black-and-white fur is expected, while rustiness or fading in black fur is seen as a fault. Any Bi Black Sheltie with more than 50 percent white fur is disqualified.
The Bi Blue Sheltie
And finally, perhaps the rarest official Sheltie color of all: Bi Blue Shelties are distinctively blue and white, with the common Irish distribution. Bi Blues also have varying degrees of merle fur. We might also describe them as Bi Blacks with merle modifications.
The Sheltie Color Genes
According to The Colors of the Sheltie: The New DNA Findings, there are at least 11 Sheltie color genes. We'll look at the major genes below, including those that control the base coat color (eg, tan), any dilution (eg, blue), and any pattern (eg, merle). Other genes control minor features, such as ticking, spotting, and progressive graying.
To help us get a handle on Sheltie color genes, here's a short genetic glossary.
|A unit of DNA that controls a trait (eg, the agouti gene).
|An alternative form of a gene that creates variation (eg, ay or at).
|The two inherited alleles of a gene (eg, ayay).
|The physical expression of a gene (eg, Pure Sable).
|The boss allele that's expressed more (eg, ay).
|The background allele that's expressed less (eg, at).
Here I've illustrated the genotypes (combination of alleles) and phenotypes (expression of those alleles) of the major Sheltie colors. Next, we'll explore the logic of how two alleles in combination (one from the mother, one from the father) are expressed in an individual Sheltie puppy.
The Agouti Gene
The agouti gene controls the amount and distribution of tan pigment in the Sheltie coat. It also controls whether the hairs on a dog's coat are banded with different colors or are a solid color. This gene ultimately produces a range of variations in the coat patterns of Shelties, leading to some unique and striking coat patterns.
As with many genes, the agouti gene comes in multiple types/variants known as alleles. Shelties have three possible agouti alleles:
- The ay Allele
- Pure Sable coat
- Full tan expression
- The at Allele
- Tri Color coat
- Limited tan expression
- The a Allele
- Black coat
- No tan expression
The Agouti Punnett Square
Sexual reproduction sees that a Sheltie puppy inherits one genetic allele from each parent. To work out the possible combinations of agouti alleles, we can plot them in a Punnett square.
The mother's possible alleles run down the left, and the father's run across the right. Match them together to predict the alleles of their offspring puppy. (Remember, sperm and egg cells carry only one allele of each gene, but all other body cells carry two copies, one from each parent.)
|at (Tri Color)
|at (Tri Color)
Bi Factoring and Tri Factoring
This is where gene interactions come in. While the ay (Sable) allele is dominant, it doesn't completely block out the effect of recessive alleles.
Thus, a Tri Factored Sable can have the phenotype of Mahogany Sable because he's fully expressing an ay (Sable) allele and partially expressing an at (Tri Color) allele.
What's more, when he matures and makes sperm, some of his swimmers will contain the ay allele and some will contain the at allele. His offspring may be Sable, Tri Factored, or Tri Color, depending on the genotype of the female he mates with.
Tri Factoring also explains the different coat colors of Howard and Piper. While both Sables were born of the same Pure Sable father, Piper's abundance of black fur suggests Tri-Factoring at play. It's likely that Piper's mother was Tri Color or Tri Factored.
The Merle Gene
I've also illustrated the genotypes and phenotypes of the Sheltie merle gene. This gene comes in two forms and controls whether black fur will be diluted down to blue and gray.
- The M Allele
- Merle coat
- Dilutes black fur
- The m Allele
- Non-Merle coat
- No dilution
Since the M allele is dominant, a Sheltie only needs to inherit one copy of it from either parent to display the merle phenotype. Here's the Punnett square showing the potential inheritance:
Interesting, unlike the agouti color gene, the merle gene is considered a color modifier gene. That's to say it interacts with other color genes and alters their expression.
Besides diluting black fur to blue and gray, the merle gene also gives a Sheltie either one or two blue eyes.
The thing about genetic mutation is that sometimes it's good (adaption) and sometimes it's bad (disease).
Breeding two Blue Merle Shelties together creates a 1 in 4 chance of producing a Double Merle puppy, which has serious health consequences. While it creates a striking all-white coat, the lack of melanin impacts the development of the eyes in the womb. Many Double Merles are born blind, deaf, or both.
While breeding two Blue Merles can produce 3 out of 4 healthy puppies, it's still pretty reckless to do so given that Shelties have litters of 4-6 puppies. Statistically, at least one puppy per litter will be born with a serious congenital condition.
Sheltie Color Oddities
With all these genetic elements at play, there are plenty of combinations that can make unusual Sheltie colors, even if we don't see them that often.
For instance, the Color Headed White (or CHW) Sheltie has a virtually all-white coat, except for his head markings. CHWs look like regular Shelties who've been dipped in white paint from the neck down.
Color Headed White Shelties were excluded from the breed standard in 1952. Nowadays, when a Sheltie has more than 50 percent white markings, he's automatically disqualified from Conformation. As a result, breeders rarely try to produce CHWs today.
Color Headed Whites don't have the hearing or vision defects suffered by Double Merles because their coloration doesn't come from the merle gene. Instead, they come from breeding two white factored Shelties together.
White Factored Shelties
White factoring refers to the extent of white markings on the coat. If a dog is white factored, it means they have an abundance of pure white fur, usually on their collar, chest, and legs. More often than not, they have a strong white stifle running up the back leg.
The gene responsible for white factoring is called the MITF gene and it directs all spotting and white markings on the coat:
- The s allele
- White Factored
- More white fur
- The S allele
- Non-white factored
Crossing two white factored Shelties produces white factored (Ss, sS) offspring 50 percent of the time, and Color Headed Whites (ss) 25 percent of the time.
|s (White Factored)
|s (White Factored)
White factored Shelties can be valuable to breeders in producing sufficient white markings in puppies. They're prized in dog conformation, as long as the white fur doesn't exceed 50 percent of the body, nor show up as conspicuous body spots.
Pure Sable, Mahogany Sable, Tri Color, Blue Merle, Bi Black, and Bi Blue Shelties can all be white factored. That's because the abundance of white fur comes from a color modifying gene, as opposed to a base color gene. White factored Shelties can also have blue eyes.
If you enjoyed learning about Sheltie color genetics, you might find it fun to experiment with this Coat Color Inheritance Calculator.