Let’s play dog show judge. We present a pop quiz for non–Boston Terrier owners:

You have three Boston Terriers in front of you: one is black and white, the dog in the middle is brindle, and the third is seal. You try to find something in each dog that will sway your assessment one way or the other, but they are so comparable that you simply can’t. Which dog do you place first?

The AKC breed standard provides the answer.  In the section on Color and Markings, it reads: “Brindle is preferred only if all other qualities are equal.”

“Equal” is pivotal word here. While it’s rare (in our view) to find three dogs so similar that the “tie breaker” comes down to color – neither is it unheard of. In such a scenario, the judge is directed to place the brindle dog in first place per the breed standard. But why?

Let’s first review the color – OOPS! Our bad. Brindle in the Boston Terrier is not a separate color but a pattern expressed on a black-based (eumelanin) coat, produced primarily by the brindle allele at the K locus. It creates alternating dark and lighter bands over the underlying pigment, with the exact appearance influenced by additional genetic interactions and modifiers, while white markings are controlled independently by the spotting locus and don’t influence whether a dog is black, seal, or brindle.

To our knowledge, seal and black share the same black pigment, with seal appearing brownish or reddish in strong light due to currently undefined or incompletely mapped modifiers that affect how densely the black pigment is expressed; brindle specifically requires the brindle-pattern allele –  without it, a black-based Boston will look solid black or seal instead of striped.

Because brindle depends on this distinct genetic variant, it can be readily diminished if breeders select only for solid black or seal. Again, as far as we know,  once largely bred out, it is difficult to recover without deliberately reintroducing the allele, which can help explain why early and historically careful Boston Terrier breeders emphasized and preserved brindle. It wasn’t just to maintain not the traditional look of the breed,  but also for allelic diversity at the K locu, instead of narrowing the gene pool to a single solid black expression. Interestingly, early breeders seemed to know to do this in their pre-genetic testing era.

In short, brindle is preferred in the Boston Terrier standard not because it’s rarer or prettier, but because it is historically correct and genetically tied to the breed’s origin and type.

Let’s remember that early Boston Terriers were overwhelmingly brindle with white markings. The foundation dogs of the breed—most notably Hooper’s Judge—were brindle, and for decades brindle was the dominant and defining color of the “American Gentleman.” As solid black dogs became more common through selective breeding, the parent club (we suspect)  retained a preference for brindle to help preserve the breed’s original look and prevent drift toward a more generic black-and-white dog that could resemble other small companion breeds.

Importantly, the wording that “brindle is preferred only if all other qualities are equal” makes clear that brindle confers no advantage over a dog that is superior in structure, balance, expression, or temperament. The preference is included in the standard solely to honor and preserve historical breed type. It is a nod, so to speak, to the Boston Terrier’s roots, but color alone is never to supercede soundness, structure, temperament, and type.

Image: By Alexunder Petukhov/iStock