What Is a Blue-Eyed Merle?

One of the most striking of all canine coat colorings is the merle pattern. Often associated with the Australian shepherd, this color pattern can be found in many other breeds as well. In addition to the colorful coat, the gene that causes the merle coloration can also affect the pigment in the eyes, resulting in blue eyes, or brown or amber eyes with flecks of blue.

  1. Merle Defined

    • The gene that causes the colorful merle coat pattern is a dilution gene. That means it lightens the coat color, providing a gray color to a black dog or a light reddish color to a liver-colored coat. The darker coat that remains tends to be irregularly placed around the body. Some dogs with the merle coloration will have only one or two lighter patches; others will have only one or two dark spots. Merle dogs may also have white trim and copper points that are not diluted.

    Eye Color of Merles

    • The same merle gene that acts on the coat color can act on eye color as well. As it is a dilution gene, it can remove the color from the iris, leaving a totally blue eye, or it can remove only part of the pigment, resulting in an eye that is only partially blue. This blue coloration may occur in both eyes or only one. Blue eyes do not affect the dog's vision, although in some breeds this eye color may limit its success in the show ring.

    Problems with Merles

    • While dogs that receive only one copy of the merle gene will experience no more health problems than any other dog, those that inherit two copies of this gene --the result of a merle-to-merle breeding -- may inherit several deficiencies. Dogs with the double-merle gene will have a coat that exhibits large amounts of white, especially over the head, and will often be deaf. In addition, they may have several eye abnormalities ranging from misshapen pupils to very small eyes.

    Breeds with Merle Coloration

    • While the Australian shepherd is the breed most closely associated with the merle pattern, several other breeds carry the gene as well. According to the Genomia website, those breeds that list the merle pattern as an approved color include the Catahoula, collie, Shetland sheepdog, border collie, Chihuahau, dachshund, Great Dane, pit bull, Pomeranian, Cardigan Welsh corgi, cocker spaniel, Norwegian hound and Beauceron sheepdog.