An adult Cesky Terrier older than three years can be any uniform shade of gray than can be anywhere from a pale platinum gray or charcoal, to a light coffee color, but all Cesky puppies are born black or chocolate brown, and a vast majority are born black and turn grey within the first few years.

And here is where we can get into trouble because geneticists, we’re not (if you are one, feel free to help out!)  It’s our understanding that two genes determine coat color pigmentation: the Agouti (or A) locus which controls phaeomelanin (or red/tan pigmentation), and the Extension (or E) locus which controls black pigmentation, or eumelanin. A “K locus” on the color genotype acts like a toggle between the two, and it’s the combination of the three loci that makes Ceskys a shade of black instead of a shade of red or tan.  Some Ceskys remain dark and don’t seem to grey, and for this reason, it’s thought that not all Ceskys have what is suspected to be a hypothetical “greying G marker.”

Needless to say, understanding the color genetics in this breed can be challenging since a Cesky’s head, ears, feet and tail can show a darker pigment, and brown, white, or  yellow markings are allowed on the beard, cheeks, neck, chest, limbs, and around the vent.  Many think that the more interesting genetic color markers are contributed by the Sealyham Terrier, part of the breed ancestry (along with Scottish Terriers, and, according to one canine historian, perhaps even a bit of Dandie Dinmont Terrier and wirehaired Dachshund).

Image: Cesky Terrier by Amy Spittle of AmySpittleArt is available for purchase here