Do masks show up on Harlequin or Merle coats?

No, a black mask is not visually noticeable on standard Harlequin or Merle Great Danes.

While the masking trait—which researchers believe is controlled by the E-series (MC1R gene)—is dominant and clearly visible on lighter base coats like fawn and brindle, it becomes camouflaged on other coat types. For dogs with solid black, blue, harlequin, or merle coats, the mask is essentially hidden because it blends in with their overall dark coloring or heavily spotted patterns.

However, even though the mask cannot be seen, Harlequin and Merle dogs can still carry the dominant mask trait. Because the trait is visually hidden in these dogs, breeders use modern DNA testing at the E-locus to uncover their genotypes. For example, if a Harlequin dog tests as homozygous for the black mask, a breeder knows with certainty that the dog will pass the mask trait to all of its puppies, regardless of the mate chosen.

It is also worth noting how the merle and harlequin genes interact with a mask if the dog has a fawn base coat. If a sable/fawn dog inherits the merle and harlequin genes (creating a “fawnequin”), the harlequin modifier will affect the black parts of the coat, which include the mask and any black tipping. In these cases, the mask and black sections of the coat are broken up into harlequin patches.