Merle and harlequin are two distinct coat patterns seen in some dog breeds. While they may look similar at first glance, there are some key differences between the two.
What is Merle?
The merle coat pattern is characterized by patches of diluted pigment interspersed with normal color. This results in a marbled or mottled appearance with darker patches against a lighter background. The merle gene causes random modifications in pigment development, so no two merle dogs will have exactly the same coat pattern.
Merle comes in different color variations depending on the base coat color. For example, dogs with a black base coat and the merle gene will appear gray or silvery blue. Dogs with a brown or chocolate base coat will appear as a lighter brown or tan with merle. The merle gene simply dilutes and breaks up the base coat color into random splotches.
Some common merle color patterns include:
- Blue merle – silvery gray and black
- Red merle – pale red/tan and darker red patches
- Liver merle – pale brown and darker brown
- Isabella merle – very pale fawn and tan
The merle gene can act on any base coat color. Merle is commonly seen in herding breeds like Aussies, Collies, Shetland Sheepdogs, and Catahoula Leopard Dogs. It also occurs in Corgis, Chihuahuas, Dachshunds, and several other breeds.
What is Harlequin?
The harlequin coat pattern is defined by large, irregular black patches against a white background. The black spots are distributed over the majority of the dog’s body, with white appearing on the legs, chest, neck, and head. The harlequin pattern always has a white base coat.
Unlike merle which produces marbled patches, the black spots in harlequin are well-defined large patches, giving the impression of a Dalmatian turned inside out. The spots are irregular in shape and placement. No two harlequin dogs will have the exact same pattern.
The harlequin pattern only occurs in certain breeds, most notably the Great Dane. It is also seen in some BMCs, Pointers, Catahoula Leopard dogs, and Beaucerons. Harlequin is relatively rare compared to other coat patterns.
The Genetic Difference
While merle and harlequin may look similar, they are caused by completely different genes. The merle gene (M) causes a random modification of pigment cells that results in the characteristic dilute patches. The harlequin gene (H) works differently to restrict pigment to defined patches against a white coat.
The main genetic difference is that merle is a dominant trait while harlequin is a recessive trait. A dog only needs one copy of the merle mutation to exhibit the pattern. Harlequin requires two copies of the gene to be visually expressed.
Here is a simple breakdown of the genetics:
- Merle – A dog with one copy of the M gene (Mm) will be merle. The trait is expressed even if only one merle gene is present.
- Harlequin – A dog needs two copies of the H gene (Hh) to show the harlequin pattern. With only one H gene (Hh), the solid color is expressed without the white patches.
The inheritance patterns are completely different. Merle is dominant, harlequin is recessive. This is the key genetic difference between the two coat patterns.
Is it Possible for a Dog to be Both Merle and Harlequin?
Since merle and harlequin are controlled by different genes, it is possible for a dog to carry both the M and H genes. However, the harlequin pattern usually masks most of the merle when both genes are present. Small merle patches may be visible on some harlequin dogs if you look closely.
For a dog to be both visually merle AND harlequin, it would need to inherit an M gene from one parent and two copies of the H gene from the other parent. This combination is rare, but can occasionally occur.
Key Differences Between Merle and Harlequin
Here is a quick summary of the main points that differentiate the two coat patterns:
- Merle produces marbled, mottled patches from diluted pigment while harlequin causes solid black patches against a white coat.
- Merle acts on any base coat color while harlequin only occurs on a white base.
- Merle is a dominant trait controlled by a single M gene. Harlequin is a recessive trait requiring two copies of the H gene.
- Merle occurs in many breeds, harlequin is rare and breed-specific.
- It’s possible but uncommon for a dog to carry both M and H genes and show minimal signs of both patterns.
How to Tell Merle vs Harlequin
Telling merle and harlequin apart is usually straightforward when you know what to look for.
Check for these signs of a merle coat:
- Marbled or mottled patches of diluted color against the base coat
- Random patch distribution with no clear pattern
- Patch colors blend smoothly together
- Any base color can be present
Signs your dog is harlequin:
- Large solid black patches against a white base coat
- Patches are irregularly shaped and placed but clearly defined
- Only appears on white coat base
- Seen primarily in Great Danes and a few other breeds
If you’re ever unsure, consider the breed. Merle can occur in many breeds, while harlequin is rare outside of a few specific breeds like Great Danes, Beaucerons, and some Pointers.
Health Issues Associated With Merle and Harlequin
Both the merle and harlequin genes are associated with an increased risk of certain health problems, primarily deafness and vision issues. However, there are some differences in the specific conditions linked to each coat pattern.
Merle health risks include:
- Deafness – merles are more likely to be deaf in one or both ears
- Microphthalmia – abnormally small eyes
- Colobomas – gaps or holes in structures of the eye
- Blindness
- Sun sensitivity
Harlequin health risks include:
- Deafness
- Ocular issues like diamond eye
- Heart defects
- Thyroid problems
- Alopecia – hair loss
The merle gene can affect hearing and vision when present in double doses (homozygous). Harlequin health issues are primarily linked to the lack of pigment. Responsible breeding minimizes risks by avoiding merle-merle pairings and using health testing.
Example Breeds With Merle Coats
Here are some examples of breeds that can have merle coat patterns:
- Australian Shepherd – Red merle and blue merle are common
- Border Collie – Often seen with blue merle coats
- Cardigan Welsh Corgi – Red merle or blue merle coats occur
- Shetland Sheepdog – Blue merle is very common in the breed
- Dachshund – Seen in dapple (merle) coats
- Great Dane – Fawn merle or brindle merle coats can occur
- Pomeranian – Orange sable merle and black-and-tan merle coats occur
There are many other purebred dogs and mixed-breed dogs that may have merle coats as well.
Example Breeds With Harlequin Coats
Here are the main breeds that can have true harlequin coat patterns:
- Great Dane – The most common harlequin breed
- Beauceron – Harlequin is one of the acceptable coat patterns
- Pointer – Some breeding lines carry harlequin
- Catahoula Leopard Dog – Rarely expresses harlequin
As mentioned, harlequin is much more rare and limited to certain breeds. Most dogs said to be “harlequin” are actually merle if they are not one of the breeds above able to carry true harlequin.
Conclusion
While merle and harlequin may appear similar at first, they are genetically distinct coat patterns. Merle produces marbled, mottled patches of diluted pigment. Harlequin causes solid black patches on a white coat. The inheritance is also different, with merle being dominant and harlequin recessive. Both patterns are associated with potential health risks, especially deafness and vision issues. Responsible breeding and genetic testing helps minimize these risks. So in summary, merle and harlequin are related visually but have clear genetic differences.