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Merle Dog: Color & Controversy


Last Updated: February 25, 2023 | 7 min read | Leave a Comment

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What do you know about merle dogs? Most dog lovers have heard the term used to describe coat color. Merle is sometimes called a color, sometimes a pattern, and appears in a canine’s coat due to a specific genetic pairing. Merle dogs are exquisite to see, and no two look the same. Many people love how these pups look but do not know much about merle dogs or the color controversy surrounding them.

Merles can come in a few different breeds, and there is much more to these dazzling pups than meets the eye. These pups often have a high price tag due to their unique appearance. They are also referred to as dapples, with a distinguishable, blotchy look. The popularity of merles has grown recently, with many people now seeking out these breeds for their unique coloring.

These dappled pups are distinguishable by their intriguing looks, and anyone who hopes to find one should learn a little more about them. That is where we jump in to help with research and information to answer all your questions. Discover more about merle dogs, their genetics, history, and the controversy around them in this quick overview.

What Is Merle?

Beatiful Aussie with Blue Merle Coat
Merle can be confused for brindle, though the two patterns are actually quite different.

Merle is a type of color pattern that appears in certain dogs. It consists of a diluted base coat color topped with splotches of deeper pigmentation. This pattern forms when the dog has two copies of the merle gene, which causes the coat to be mottled with patches of different colors. This gene is responsible for the spotted, blotchy appearance in the coat and passes it down from each generation to generation. The gene is recessive, meaning that if a dog has only one copy of it, it will not exhibit the dappled pattern. This color pattern can vary from dog to dog but is often present in canines with black, brown, blue, red, or silver coats. Merles also stand out for their unusual eyes, which are often two different colors.

Brindle is a base color with striped-like markings, and merle is haphazard blotches of colors on a lighter base coat. There is something called a cryptic or hidden merle. This happens when a pup has a significantly faded, almost indiscernible pattern. The pattern can be hidden, and canines may need DNA testing to see if they carry the gene.

Merle Genetics

Both a dominant and recessive trait is involved in creating the blotchy appearance. Merle happens when a pup, regardless of breed, has only one copy of the (M) merle allele, which is semi-dominant. The (m) non-merle allele is recessive, so canines with heterozygous Mm genotype are merle, and those with the homogeneous mm genotype are not. Only one M needs to be present to deliver the irregular pigments in the coats of a dappled dog. This coloring randomly affects different coat areas leaving small spots and patches of the base coat color to shine through. Mm is referred to as the standard or classic.

A dog can be born with two copies of the M allele, resulting in a genotype of MM. This is a double merle or double dapple. These pups do not look the same as the classic merle. They have mainly white base coats with a few larger blotchy patches. These canines may have some inherent genetic and health issues, and owners are not recommended to breed them.

Two variations of merles have been recognized in recent years: the dilute and harlequin. Dilutes have a diluted coat with no noticeable blotchy patches. Harlequins have light base coats with blotches of deep pigmentation.

Merle Coloring In Dogs

The dapple coloring in canines is quite spectacular to see. Because it results from a genetic mutation, no two look exactly the same, even if they are the same breed or the same litter. Dogs in the same litter can also not be dapple marked. It all depends on the exact blend of genetics in place.

Merles usually have mottled coats with a combination of white, tan, and black. Patching is often lighter and can be shades of blue to gray or even shades of red (sometimes called liver), including brown and black. They also usually have oddly colored eyes, a condition called heterochromia, or blue eyes. Some can also have brown eyes.

Merle Dog Controversy

Two Happy Merle Dogs
There has been some controversy over the years regarding breeding this color breed.

Blue Weimaraner breeds and other merle dogs’ genetics can predispose them to specific health conditions, including poor vision and hearing. This gene combination may happen naturally in some canine breeds. It was artificially introduced in others by crossbreeding, where the controversy lies. This practice has led to protests of this crossbreeding, as it introduces possible defects and health conditions not previously present in some breeds.

When two merles are bred together, the puppies can inherit two copies of the M gene. Two M’s often leads to various health problems. These problems can include eye and ear defects and an increased risk of skin, heart, and neurological issues. The controversy has led to some breeders turning away from merle-to-merle breeding while other breeders continue to breed them together to produce puppies with desirable color patterns.

The American Kennel Club (AKC) stopped recognizing this as a color in breed standards for several breeds due to the increased risk of impaired hearing and sight. However, purebreds of any breed and color can register as long as they have the appropriate paperwork of registered parents.

Why Can’t You Breed Merle-To-Merle?

In addition to the controversy regarding M-to-M breeding, some health concerns are also associated with this type of color pattern. Pet parents should be aware of these potential health risks and make sure that they are only breeding with other dogs that do not carry the M gene.

Some potential health risks associated with MM coloring in canines include eye, ear, skin, heart, and neurological problems. Please note that these health issues can pass down from generation to generation. Make sure to be aware of any potential risks before breeding merles together.

Main Health Concerns For Merle-To-Merle Breeding

Homozygous or double M dogs are at a higher risk for specific health issues. The most prevalent are vision and hearing issues. Breeding specifically for the dominant M gene also puts them at an elevated risk of hereditary health issues. A significant concern is the risk of deafness and blindness. This is because the M gene can disrupt the development of both the inner ear and eyes, resulting in partial or complete loss of hearing and vision.

  1. Deafness – These pups can have inherited deafness. This can happen in one ear or both and may even mean complete deafness. Some breeds are more prone to deafness and will have a higher chance of auditory malfunctions if they are MM. Dogs with the piebald gene, which makes canines white, are often more likely to be deaf if they are a double M.
  2. Blindness – Double dapples are often wholly or partially blind. They can also be both deaf and blind.
  3. Microphthalmia – This is a condition in which the eyes are tiny. Most often, they do not function correctly or at all. The pupils grow abnormally large or small. There is no known reason why the MM genotype may connect to this condition, though scientists have studied an association with the microphthalmia transcription factor (MTF) gene.
  4. Retinal dysplasia – This is an often-inherited condition that causes the eye to form improperly. This condition worsens over time and can lead to complete blindness. It can also lead to a retinal detachment which is very painful.
  5. Skin Concerns – M-to-M breeding can also result in a higher incidence of skin issues, such as a lack of pigmentation in the skin and hair, also called “double merle” or “lethal white.” This can lead to sun sensitivity and an increased risk of skin cancer.

Generally, it is wise to be cautious when breeding dapples, as the potential health issues can be severe. It’s often recommended to avoid breeding two dapples together to reduce the risk of these health issues. Always genetically test a pup that has dapple siblings or parents before breeding to avoid a double M.

Merle Dog Breeds

Several canine breeds carry the M gene, including the Australian Shepherd, Miniature American Shepherd, Collie, Shetland Sheepdog, Dachshund, Cardigan Welsh Corgi, Great Dane, Chihuahua, Pomeranian, Mudi, and the Catahoula Leopard dog. Each of these breeds has its unique look, with the dapple pattern adding a distinctive touch.

We must point out that not all merle dogs are the same, and the color pattern can vary from one breed to the next. For example, the Australian Shepherd has a blue splotchy pattern, while the Catahoula Leopard dog has a red dapple pattern.

Best Ways To Care For Merle Dogs

Merle Corgi
Merle Corgis will most likely come along with a spotty coat.

Once you have decided to adopt a dapple pup, it is essential to take the necessary steps to ensure that your dog is healthy and happy. This includes providing your pup with the proper nutrition, exercise, and socialization. It is also essential to ensure that your dog is up to date on all vaccinations and vet visits.

The good news is that these dogs do not need special care or treatment. They are typically healthy and happy. The main worry comes when breeding two M’s together, which is highly discouraged. Always get a DNA test if you are not sure your fur baby is a dapple before doing any breeding. This will help prevent the chance of double dapple breeding. Remember that different breeds are susceptible to health issues, and some may need special care, for example, giant breeds like the Great Dane. All dogs should be fed age-appropriate food and size-specific formula regardless of breed.

Final Thoughts

Merle dog breeds have become increasingly popular due to their unique coloring and loyal and intelligent personalities. While these pups make excellent companions, it is vital to stay aware of potential risks associated with this dapple coloring and the controversy surrounding their breeding. The splotchy coated pups come in many different breeds and crossbreeds, so it is advisable to investigate your dapple dog’s background if you plan to breed.

It is also essential to ensure that your pup is provided with the appropriate nutrition, training, exercise, mental stimulation, and socialization to ensure its health and happiness. By taking these steps, you can ensure that your dapple dog is a healthy and happy member of your family for years to come. If you are considering adding a merle dog to your family, research and learn all you can about the potential risks associated with these breeds. With proper care, your dapple doggy can be a loyal and loving companion for years to come.

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