Color genetics in Kooikerhondjes

Kooikers are NOT a typical “color breed” – the breed standard describes them as an orange and white dog with black pigment, and there are no other acceptable colors. Their color genetics are thus not as convoluted as those breeds that come in a range of colors, but the variation between Kooiker individuals sometimes surprises people nonetheless!

Kooikers are genetically sable dogs, not true orange or red dogs. This is why they are orange dogs, but also have black skin pigments, black hairs on their ears known as earrings, and occasionally black tailbase rings, black hairs interspersed in the coat, and/or black-tipped guard hairs. Kooikers have the agouti gene ay and express both forms of pigment – eumelanin (black pigment) and phaeomelanin (red pigment) in their coats. The agouti gene allows for “banded” hairs, where the color of each hair shaft changes depending on the pigment deposited during its development. This is an ancestral condition – many wild animals, including wolves, have agouti coats. While here, “agouti” is a genetics term, “sable” is a dog-world term, and specifically Kooikers are what is known in the dog world as a “tipped” sable. Sable dogs are generally defined as having at least some guard hairs that are tipped with black, but they may be a different color at the base of the hair, and in turn the undercoat may also have a non-black color. In Kooikers and breeds with similar genetics like collies, the extent of the black pigment on guard hairs has been selected against by breeders, so while it’s theoretically possible, it’s unlikely that dogs with lots of black hairs are born. There are Kooikers, however, whose coats are so heavily black-tipped that they appear black or tricolored from a distance, but on closer examination have orange hair at the base of the guard hairs and also have orange undercoat – this is a perfectly acceptable color variation in the breed.

Typical Kooikerhondje color gene test results

A (Agouti) Locus – ay/ay: dog is sable

B (Brown) Locus – B/B – dog is NOT brown or liver

E (Extensions) Locus – E/E – no effect, the dog will be the color determined by the A locus

S (Spotting) Locus – sp/sp – the dog will have a white piebald spotting pattern

All other loci (including dilution, albinism, K dominant black, RALY, merle, harlequin, etc.) – no known abnormal alleles

T (Ticking) Locus – unclear, likely T/T or T/t

“Normal” Kooikers are essentially always orange-to-black agouti, always piebald-spotted, and never diluted, yellow, brown, or albino. They often display ticking, but the variation from nearly-unticked dogs to heavily-ticked individuals indicates likely all alleles are at play in the population. However, without any real color genetics research on Kooikers having been done, much of their genotype is extrapolated based on findings from related breeds. (And for this reason I reserve the right to edit this article in light of any future findings!)

Development

Because sabling has to do with the actual growth of each individual hair, the “coat color” of a Kooiker puppy changes as its coat grows out. When Kooiker puppies are born, they appear very dark brown or even tricolor – black and white with tan points on their cheeks. Their coats grow in rapidly and they acquire their permanent orange color within days or weeks. As their guard hairs grow in (including the black hair constituting their earrings, and sometimes a black tailbase ring) black or black-tipped hairs may appear in the coat, especially on the back. Ancestral-appearing black dorsal stripes within the orange patches may occur in puppies but are usually lost when the adult coat fully grows in. This is due to the agouti gene again – think of a litter of wolf puppies that are born black or very dark brown, that will ultimately mature into the variety of blacks, greys, whites and reds that are seen in wild wolves around the world today. Color also tends to “grow” into the white areas of the body as puppies age – puppies born with only narrow strips of white separating two patches of orange will likely have two connected orange patches as an adult.

A scan of a print of a 3-month-old Kooikerhondje puppy showing dark pigment across the back that was later lost

Tricolors

Occasionally, Kooikers are born true tricolor (true black and white with orange points), which is a show-ring and breeding disqualification. This suggests that the at (tan-point) gene variant exists in some members of the population, although I have not personally seen the results of any genetic tests for a tricolored dog, or the parent of a tricolored dog. The regular agouti ay gene is incompletely dominant to the at gene, and a dog with one or two copies of the ay gene will appear “normal” as it will mask its at gene. However, if a puppy gets two copies of a recessive at gene from its ay/at parents, it will appear tricolor. Tricolors differ from heavily sabled Kooikers in that the undercoat and the entire length of every pigmented guard hair will be black – this speaks to the lack of the banded agouti gene. There is some evidence that heavy sabling in “normal” colored dogs may be the result of incomplete dominance from a heterozygous ay/at condition, but without real research, the correlation cannot be totally validated.

There are also very occasionally black and white Kooikers born. I have never seen one in person, nor has anyone I know, but reports of them tend to be associated with litters whose paperwork may be somewhat less than watertight. For that reason and in the absence of true genetic research on color in Kooikers, I won’t speculate here on the genetic basis of black and white dogs.

Extent of color and color deposition

Extent of white spotting or piebald appears to be breed-dependent but is also not very well researched, especially in Kooikers. Kooikers appear to be homozygous recessive for the S or Sp gene, causing a relatively significant amount of white on their bodies. The ideal Kooiker is 51% orange and 49% white, with white feet and legs, tail, underparts, chest, muzzle and blaze. Some individuals with unbroken color across their backs are termed “mantle” (or “mantel”) but this is not the same mantle or Irish spotting that has a genetic basis in other breeds with only one copy of the S allele. In fact, extent and placement of white spotting in an sp/sp dog appears to be both breed-dependent, and very unpredictable with current methods and tests. Read an excellent explanation of “Spread of White” here. Many breeds with this degree of high-white piebald spotting have been shown to have congenital deafness due to gene linkage (a classic example is the Dalmatian). Anecdotally, Kooikers don’t seem to experience this, perhaps because of a protective effect of the genes for melanin being expressed near developing ears, but this is an area that could use real research.

In Kooikers, breeders tend to select for non-mantle dogs (those with clearer, distinct spots) and those with both eyes surrounded by orange (one or both eyes in white hair is termed a pirate or piraat). Scientifically, there is little evidence that the exact amount and placement of color in piebald dogs such as Kooikers is as simple as breeding two similarly-marked dogs together. Breeders would likely disagree, based on coloration of puppies from both very white and very orange parents seeming more likely than not to resemble a parent, but there is no genetic research I can find that supports or refutes this. We know that pirates and mantles can both be produced by parents who themselves are “normal,” but also that parents who are pirate or mantle can produce “normal” puppies. It’s important to remember, however, that per the standard, extent and placement of color is to be considered only as a “tiebreaker” between two otherwise-equal dogs – while it is the easiest attribute to judge, it is also meant to be the least important in Kooikers.

Lookalikes

There are many breeds and mixes that are mistaken for Kooikers, since sable + piebald is a relatively “easily expressed” color scheme – the agouti or sable especially, being an ancestral condition, is likely to crop up in every non-Spitz breeds. The piebald, or white-spotting, can be acquired through one white-spotted parent, and the agouti gene can come from any number of parent breeds that are not Spitzes. Some color genes may offer clues to presence or absence of Kooiker parentage. The B locus causes browns, but Kooikers do not have mutations causing livers or browns, and for this reason their pigment in their skin, eyes, and lips is not the lighter color seen in a breed they’re commonly confused for, the Brittany. Orange and white American-style Brittanys are b/b (recessive brown) and e/e (recessive orange, in this case) neither of which mutation occurs in Kooikers, so while their colors may be similar, they “achieve” those colors differently, in a genetic sense. While presence or absence of black earrings does not make or break a Kooiker, dogs with orange and brown pigments “b” alleles without the agouti genes (like Brittanys) cannot have earrings or black points.

Kooikers are also “normal” or E/E in the Extension locus, meaning they cannot have dark masks or grizzle patterns (tan underneath with darker pigment overlaid on the top of the dog). No true Kooiker has a darker face mask, but the masked Em allele is dominant to the Kooikers’ E allele, meaning evidence of a mask especially in an adult indicates at least one parent is not a purebred Kooiker.

This post is based on extrapolation from research in other breeds, and limited results from DNA panels of Kooikers. If anyone has a DNA panel from a Kooiker that supports or refutes anything I have written, I welcome that feedback. Again, color genetics in Kooikers has not been formally studied so most of this article is essentially speculative and simplified. – G