The merle coat pattern in dogs refers to a mottled patchwork of colors and lightened areas, often with darker patches creating a dappled appearance. This unusual and eye-catching coloring has become popular in some breeds like French Bulldogs, but there is debate over whether merle is a natural color for this breed or the result of crossbreeding with other merle dogs.
The Controversy Around Merle French Bulldogs
Merle is not listed as an accepted color in the breed standard for French Bulldogs, which only recognizes 11 colors/patterns: fawn, brindle, white, cream, red, black and tan, black, black and white, black and fawn, fawn and white, and brindle and white. So in the show ring, merle Frenchies would traditionally be disqualified.
However, merle French Bulldogs have surged in popularity as pets in recent years. Breeders have intentionally mixed Frenchies with other merle breeds like Chihuahuas, Pomeranians, Shetland Sheepdogs, and Aussies. This introduced the merle genes into French Bulldog bloodlines and allowed breeders to produce the distinctive merle pattern.
But many French Bulldog breed purists argue that merle is not a natural color for the breed. The concern is that introducing merle through outcrossing also brings in other undesirable traits or health issues not typical of the Frenchie breed. Responsible breeding associations like the AKC ban registering merle French Bulldogs for this reason.
Genetics of Merle Coloring in Dogs
The merle pattern is produced by a dominant gene variant known as the M locus. All dogs have two M alleles, with possible combinations of:
- M/M = Double merle. Merle coloring.
- M/m = Merle carrier. Merle coloring.
- m/m = Non-merle. Solid color.
To have merle puppies, only one parent needs the dominant M allele. But both parents must at least be carriers to possibly produce double merles, which brings health risks like deafness and blindness.
Here’s a table showing the potential combinations when breeding two merle carriers:
|25% MM (double merle)
50% Mm (merle)
25% mm (solid)
So even when two merle carriers are bred, only 25% of the puppies on average would inherit a double merle genotype and associated health issues. But due to the unpredictable results, purposefully breeding two merles is generally avoided.
Concerns Around Breeding Merle French Bulldogs
Opposition to merle French Bulldogs generally focuses on three areas of concern:
- The merle gene was introduced through outcrossing with other breeds, incorporating non-Frenchie traits.
- Inherited health conditions associated with the merle gene like blindness and deafness.
- Continued outcrossing needed to maintain the merle coloring in French Bulldog lines.
Critics argue that responsible breeding should aim to preserve the integrity of the French Bulldog’s breed standard and avoid introducing health issues. The merle pattern raises concerns in both these areas.
Introducing Foreign Breed Traits
To introduce the merle gene, French Bulldogs were crossed with other breeds like Chihuahuas, Pomeranians, Shetland Sheepdogs, and Australian Shepherds. These breeds all have a long history with the merle pattern in their lineage.
Along with adding in the dominant M merle allele, outcrossing brings in other genes that influence appearance, temperament, health, and physiology. So there is valid concern around merle Frenchies exhibiting non-standard traits or a less predictable phenotype.
Breed purists argue that randomly mixing genes from other breeds pollutes and dilutes the qualities that make French Bulldogs unique. They believe adding merle through outcrossing should be avoided to preserve the integrity of the breed.
Health Issues Associated With Merle Genes
One of the biggest concerns around the merle pattern in all dog breeds is an increased risk of deafness and vision impairment, especially with double merles. The merle gene is linked to auditory and ophthalmic abnormalities.
Studies show deafness prevalence is around 18% in dogs with the merle pattern. Rates are even higher in double merles, affecting 65-85% of dogs homozygous for merle. Blindness is also more common. These are serious health and quality of life impacts.
Even beyond hearing and vision problems directly linked to merle, there is concern that outcrossing could introduce a variety of non-Frenchie health conditions. Breeding two merle carriers is unpredictable, so each litter is a genetic experiment.
Need for Continued Outcrossing
A final objection to merle French Bulldogs is that the color cannot be maintained without continued outcrossing to other breeds. The merle gene is dominant, but there must be at least one M allele passed on to offspring to preserve the pattern.
With both parents as French Bulldogs, there are no purebred breeding options for merle Frenchies that don’t result in some non-merle puppies. Outcrossing for future generations would be required to sustain merle coloring.
So while first generation merle Frenchies exhibit the desired pattern, maintaining it long-term necessitates crossing with other breeds. This contradicts the goal of purebred breeding.
Arguments That Merle Is Acceptable in French Bulldogs
Despite opposition from breed purists, there are also arguments in defense of breeding merle French Bulldogs:
- Merle Frenchies are still over 90% Frenchie genetically after initial outcross.
- Responsible breeding can reduce risks of inherited disorders.
- Merle introduces desired coat color diversity.
- Breed standards evolve and change over time.
Breeders and owners of merle French Bulldogs don’t believe their dogs should be penalized or banned simply for having the merle pattern.
Mostly French Bulldog Genetics
While introducing the merle allele requires initially crossing with another breed, progeny only inherit around 5-10% of DNA from the non-Frenchie parent. So genetically, merle Frenchies are still over 90% French Bulldog.
Advocates argue this small amount of genetic influence from another breed doesn’t significantly sway appearance or temperament away from the French Bulldog standard. The differences are minor compared to variability within purebred French Bulldog lines.
Responsible Breeding Can Reduce Health Risks
No dog breeding is without risk of inherited disorders. But advocates counter that health issues associated with merle can be mitigated through responsible breeding practices:
- Testing hearing and vision in merle breeding dogs
- Not breeding two merle partners together
- Outcrossing to diversify genetics
- Early veterinary screening of litters
These steps help exclude medical issues from being passed on and allow merle to be integrated into breeding lines responsibly over generations. With care, merle French Bulldog health is comparable to other colors.
Desirable Coat Color Diversity
Another defense of merle breeding is that it simply introduces more diversity in aesthetically pleasing coat colors and patterns for French Bulldogs. As a popular companion dog, many owners appreciate the unique look of the merle pattern.
Merle has also gained acceptance in other breeds like Aussies, Collies, Corgis, and Shelties. So proponents argue there’s no reason it can’t become an accepted part of the French Bulldog breed as well over time.
Breed Standards Change
Finally, advocates point out breed standards are not static. They evolve based on breeder and buyer preferences, along with genetic health and diversity considerations. Responsibly integrating merle allows more options without undermining what makes French Bulldogs an excellent companion breed.
Just as brindle and fawn Frenchies bred today would have been disqualified a century ago, merle could similarly transition into an accepted part of the breed. Breed standards ultimately exist to preserve what is essential about a breed rather than gatekeep specific colors.
The debate around merle French Bulldogs involves issues of breed purity, health, aesthetics, diversity, and evolving breed standards. There are valid concerns with initially introducing the pattern through outcrossing and the potential hearing and vision issues associated with the merle gene.
However, with care taken in breeding selection, most risks can be avoided. And genetically, merle Frenchies are overwhelmingly still French Bulldog. The merle pattern simply brings desired coat color diversity.
Overall, it seems possible for merle to eventually become an accepted part of the French Bulldog breed standard, just as other colors like brindle have transitioned from controver