Welcome to the Corgi Corner! This series is posted on the first Saturday of every month! These posts help spread education and awareness on topics like general dog care, corgi specific things, medical care, health facts, etc. This month’s Corgi Corner post will be all about double merle genes! First, what is merle? Merle is a specific type of coat coloring that some breeds may have. The merle coloring is the result of the dog having one copy of the merle gene. The one copy of the merle gene causes the marbling effect on the coat and creates lighter spots throughout the solid color coat. The gene affects the distribution of pigment in the coat, eyes, and sometimes skin. Merle dogs often have blue or partially blue eyes, and their noses and paw pads may be mottled with pink. A double merle dog can be created when two merle dogs are bred together. When two merle dogs are bred together, each puppy in the litter has a 25% chance of being born a double merle. This causes the affected dog to carry two copies of the merle gene rather than just one. It does not matter what color the merle is or what the breeds of the two merle dogs are. In double merles, the marbling/lightening effect is doubled and the coat becomes predominantly white. While they can be completely white, they are not albinos. The biggest problem with double merle dogs is they are very likely to suffer from hearing and/or vision impairments and, in some cases, complete blindness and/or deafness. Deafness and hearing impairment happen due to a lack of pigment in the inner ear. Blindness and vision problems are due to congenital eye defects. Now, there is also something called a cryptic merle. Cryptic merles are dogs that carry one copy of the merle gene but show only very slight merle coloration, and in some cases, it’s not visible at all. So it may not always be physically obvious that a dog carries one merle gene. Even though the merle gene is dominant and can be seen most of the time, genetic testing of both dogs before breeding is important to ensure that both dogs do not carry the merle gene. This is where reputable breeding practices become imperative. Reputable breeders will test for this before matching two dogs for breeding, because they do not want to produce double merle puppies. Sadly, double merles happen often with non-reputable breeding practices. Non-reputable breeders often think that breeding two merle dogs together will increase the chance at producing merle puppies. But, as shown in our photo, that is not the case. Many people are often very drawn to merle colored dogs, and they tend to be in high demand. Therefore, non-reputable breeders feel they can charge more for them. At the end of the day, it’s all about money for them. There are several breeds that carry the merle gene, including Australian Shepherds, Cardigan Welsh Corgis, Border Collies, Dachshunds, Great Danes, Shetland Sheepdogs, and mixes/designer breeds. Pembroke Welsh Corgis do not carry naturally carry the merle gene, only Cardigan Welsh Corgis do. So, there is no such thing as a “purebred merle Pembroke Welsh Corgi”. They have to be mixed with something in order to get the merle gene and coloring. This has led to people now mixing Pembrokes and Cardigans, often referred to as “American Corgis”, in order to get a merle colored Pembroke looking corgi. Many people believe that this crossing is better because it will prevent the double merles from happening like they do in Cardigan Welsh Corgis. But, that is not the case at all. Double merles can, and will, still happen in “American Corgis”. If two “American Corgis” are bred together and they both carry the merle gene, there is still a 25% chance of each “American Corgi” puppy having two merle genes resulting in a double merle. Like all genetic conditions, double merles are 100% preventable with genetic testing and reputable breeding practices. There is no reason for double merles to still exist this day and age. Reputable breeders will test their parent dogs prior to breeding to determine if they carry a merle gene. Especially since cryptic merles do exist and it’s not always obvious that a dog carries the merle gene. Unfortunately, even with the ability to do genetic testing, double merles can still be seen in Cardigan Welsh Corgis, and now American Corgis, because of irresponsible breeding practices by backyard breeders and puppy mills.