Identifying Merle

After one of my recent Guess the Genotype posts, I though I would discuss in more detail how to identify a merle dog. It seems that many people have issues telling the difference between a dog that is merle and a dog that isn't merle. All of the dogs I will be looking at are often described as "blue" thanks to the pale, gray-ish parts of their coat. So, here we go:

Dogs that are merle
Remember: the merle gene will almost always only affect black pigment in the coat. Merle can also never breed true and thus you can never have a breed that only comes in merle. Breeding two merles together will always produce a little that is half merle, one quarter non-merle and one-quarter double merle. Double merles have a very high incidence of health issues such as deafness and blindness. If a dog's breed always comes in a certain color (i.e. the color breeds true) it's most likely not merle.

Some tips on picking out a merle dog: 

• The dog has a patchy grey and black coat with clear white markings (i.e. few or no colored hairs mixed in with the white). 
• Any red on the dog is one even, consistent color. 
• Dark and light patches on the body are randomly distributed and uneven in size and shape. They will often appear jagged.
• The dog has loss of pigmentation (i.e. pink spots) to the nose. 
• Eyes not only one color: part is blue and part is brown.
• The dog is blind and/or deaf (double merles only)
• The dog's pupils are of an odd location, size, or shape (double merles only)
• The dog has abnormally small eyes (double merles only)

Koolie. This dog is a tricolor merle (black with tan points, Irish white, and a single merle gene). Note the clear white markings, even tan, and uneven distribution of black and grey patches.

Mudi. This dog is a solid black merle (dominant black and a single merle gene). Note the random distribution of black and grey patches.

Great dane. This dog is bicolor merle (dominant black, Irish white, and a single merle gene). Note the clear white, uneven distribution of black and grey patches, and the loss of pigment in the nose.

Catahoula leopard dog. This dog is merle and tan (black with tan points and a single merle gene). Note the even tan and uneven distribution of black and grey patches.

Cardigan Welsh corgi. This dog is merle and white with brindled points (black with tan points, the brindle gene, Irish white, and a single merle gene). Note the clear white, uneven distribution of black and grey patches, loss of pigment in the nose, and evenness to what red can be seen.

Catahoula leopard dog. This dog is solid black merle with residual white (dominant black with a single merle gene). Note the clear white patch on the chest and uneven distribution of black and grey patches. There is also a brown spot in one eye.

Miniature smooth dachshund. This dog is a tricolor merle (black with tan points, Irish white, and a single merle gene). Note the clear white, uneven distribution of black and grey patches, and even tan.

Dogs that are not merle
Remember: these dogs do not have a copy of the merle gene. All of the dogs seen below have light areas that are genetically white, but with ticking and/or roaning genes that add color back into that white. These dogs will be born with clear white markings that will have colored hairs added in as the dog ages. Generally, after maturity the dog won't change much more. Unlike merle, this color can also breed true.

Some tips on picking out a non-merle dog:

• These dogs will never have clear white markings. 
• Black and red in the coat will be affected in the same way, so red will appear lightened as well. 
• Dark patches will be in a predictable pattern with crisp outlines and regular size.
• Dogs will most likely have fully pigmented (black) noses and (brown) eyes.

English cocker spaniel. This dog is black roan (dominant black, piebald white, and the roan gene). Note the lack of clear white markings and the even borders between the dark and light areas. The patches also match with what can be expected on a piebald dog.

Australian cattle dog. This dog is black and tan roan (black with tan points, extreme white piebald, and the roan gene). Note the lack of clear white, the noticeable patch over the eye and ear, and the different in tan between the area around the eye and elsewhere on the body. The patch also matches what can be expected on an extreme white dog.

Border collie. While border collies can be merle, this dog is black roan (dominant black, white Irish, and the roan gene). Note the lack of clear white and the even borders between the dark and light areas. The patches also match would can be expected from a border collie without roan.

Bluetick coonhound. Another black and tan roan (black with tan points, piebald white, and the roan gene). Note the lack of clear white, the presence of variation in the tan, and the clear boundaries between dark and light areas. The patches also match with what can be expected from a piebald dog.

Identify these dogs: Merle or not? 
I've included the answers in white text, so if you highlight below each image you will see your answer.

This dog is believed to be an Australian cattle dog mix and is not merle.

This mix is merle. Though the owner believes him to be part Australian cattle dog, I don't think he is.

This believed Australian shepherd mix is not merle.

This believed Australian shepherd mix is merle.

This believed Australian shepherd mix is merle.

This believed Australian cattle dog mix is not merle.

This believed Australian cattle dog/Australian shepherd mix is merle, but also appears to be roan.

I hope this helps. Remember: wherever I mention black hair, the statements also hold true of the dilutes of black: liver, blue, and fawn. Both merle and roan are commonly seen in liver, though prevalence depends on the breed. Blue and fawn are, generally, more unusual.

Now with more color: Merle or not merle?

This wirehaired pointing griffon is not merle.

This believed Australian shepherd mix is merle.

This believed cattle dog mix is not merle.

This dachshund is merle.

This Australian shepherd is merle.

So, after identifying a dog as merle, it should be a bit easier to identify its breed. For example, if a dog is merle than the likelihood of it being an Australian cattle dog mix is very low. It's more likely the dog has one of the breeds that is known to come in merle, such as the Australian shepherd, many of other herding breeds, or maybe Catahoula leopard dog.  If the dog is roan, it may very well be part Australian cattle dog or another breed with prominent ticking or roaning, such as many pointers.
 
All images are from Wikimedia Commons or Flickr.com and are either under Creative Commons licenses or are copyright free. Links to sources are available under each image except for the guessing game images. Guessing game images: one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, .