The Genetics Behind Chocolate and Black Cavaliers
One of the most exciting things about breeding Cavalier King Charles Spaniels is seeing the wide variety of coat colors that can appear in a litter. While most people know the four traditional colors — Blenheim, ruby, tricolor, and black & tan — Cavaliers can also come in striking shades like chocolate, black, and black & white.
In this post, we’ll look at the genetics behind Cavalier colors, focusing on the role of the B locus (B/b) and K locus (KB/ky). Understanding these coat color genes helps breeders predict when a litter might produce rare Cavaliers such as chocolate Cavaliers or black and white Cavaliers.
The B Locus (Black vs. Chocolate Pigment)
The B locus determines whether a Cavalier’s pigment is black or brown (chocolate):
B (dominant) = black pigment (seen in tricolors, black & tans, black & whites).
b (recessive) = chocolate pigment (seen in chocolate tricolor, chocolate & tan, chocolate Blenheim, etc.).
To produce a chocolate Cavalier King Charles Spaniel, a puppy must inherit two copies of the recessive b gene (bb). A dog that is Bb will look black but carry the chocolate gene — meaning it can still produce chocolate puppies if paired with the right mate.
The K Locus (Tan Points)
The K locus helps determine whether or not tan points appear:
KB (dominant black) = creates a solid black coat or black and white (unless chocolate is present, then solid chocolate or chocolate and white).
ky (recessive) = allows the A locus (tan points, tricolor, etc.) to show through.
Most Cavaliers are kyky, meaning they cannot produce tan point suppressed puppies. If a Cavalier is KBky, they can produce both puppies with tan points as well as puppies without tan points. If a Cavalier is KBKB, they can only produce puppies without tan points.
Putting It Together
A bb dog with KB can be solid chocolate or chocolate and white.
A bb dog with ky can be chocolate tricolor, chocolate & tan, chocolate blenheim, or full chocolate ruby depending on the other genes involved.
A B_ dog (BB or Bb) with KB can be solid black or black and white.
A B_ dog with ky can be black & tan, tricolor, ruby or blenheim.
Why This Matters for Breeders
Understanding these genes lets breeders plan pairings more carefully. For example:
Breeding two Bb carriers can produce chocolates even if neither parent looks chocolate.
Breeding two KBky dogs increases the chance of producing solids (black or chocolate).
Pairing chocolates with chocolates (bb x bb) will always produce chocolates, no matter the pattern.
Black, black & white, and chocolate Cavaliers are all part of the same genetic family — different letters at a few key loci (B and K) combine to create the beautiful range of Cavalier colors. With testing and careful planning, breeders can predict and purposefully work toward certain colors while keeping health and temperament the top priorities.