Catahoula Issues » The Merle Gene  

The Louisiana Catahoula Leopard Dog is known for its unique coloration. This coloration occurs by means of the merle gene, which is a dominant gene that causes a dilution of the solid colors, as well as creates the varying hues within a specific color. The unique coloration created by this gene may also be seen on the coats of the Australian Shepherd, Collie, Great Dane, Beauceron, Shetland Sheepdog, Dachshund, and other breeds displaying the mottled coat.

Although they are known for their amazing colors, there are Catahoulas that are not so colorful. There are many solid colored Catahoulas that provide the desired objective with just as much dedication as those with all the colorful spots. Whether there is a display of colors or just one solid color, you will find their attributes to be equal. Many owners that work or hunt with a Catahoula do not care about the color of their coat or eyes. Their only concern is that the Catahoula performs the job required.

For many years the Catahoula had been grouped with those breeds mentioned above, and it was believed that the merle gene affected all of the breeds in the same manner. Through genetic DNA research we now know that there are modifiers of the merle gene in the Catahoula. It may sound like double talk, but the merle gene, a modifying gene, is being modified, making merle in the Catahoula appear differently than in other breeds.

Here are the facts compiled from genetic DNA studies performed at Louisiana State University, Texas A&M University, Cornell University, Auburn University, Clemson University, and the University of Virginia.

• The Louisiana Catahoula Leopard Dog may be either non-merle, single merle, or double merle.
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• The merle gene carried by the Catahoula is the same that is found in other breeds.
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• There are likely modifiers of merle in the Catahoula that make merle behave different from other breeds. Although the merle gene in other breeds is similar in its effects, the modifiers in the Catahoula seem to reduce deafness.
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• Breeding a double merle pair does not produce a greater amount of deafness in the offspring than when breeding single merle subjects.
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• The merle gene affects white in the same manner as other colors. The effects of the gene on white are not seen because white cannot be phenotypically lightened.
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• In an independent study for the presence of the piebald gene, double merle dogs displaying Irish spotting where chosen from four unrelated kennels. One of the lines showed positive as a carrier of the piebald gene. This indicates that piebald is present in some Catahoulas.
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• It is apparent that Irish spotting may be produced in double merle without the presence of the piebald gene.
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• Piebald is divided into four sub-groups of genes. The one that is most readily identifiable is the one known as Irish spotting. Irish spotting will present itself as a blazed face, ring neck, white feet, and white tip on the tail.
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• Dogs carrying both double merle and piebald genes have a greater propensity for producing deafness in their offspring.
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• DNA testing for the presence of double merle and/or piebald genes is the only means of positive identification. These two factors cannot be phenotypically distinguished in the Catahoula.
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• Litters containing as little as one deaf offspring should be an indicator that the pair producing the litter should not be bred together again. Breeding with different mates may produce better results.

Laboratory studies have indicated that merle and double merle Catahoulas are being used in breeding programs more often than originally believed, or realized. There are many colored dogs with normal hearing that have been DNA tested and proven to be double merles.

These tests have given way to the hypothesis that there is a tremendous amount of the phantom merle allele contained in the Catahoula. Many dogs that are phenotypically identified as solid-colored, non-merle Catahoulas may actually be merles. This is known as ghost merle, cryptic merle, or phantom merle, and can only be detected with DNA testing. The breeding of a solid-colored dog to a merle dog may appear to be a safe method of breeding; however, not knowing for certain that the solid colored dog is actually a non-merle, may result in the inadvertent breeding of merle to merle.

In the past, a double merle Catahoula, which has been phenotypically identified by many breeders as a dog displaying more than a 70% white coat color, may actually have a full colored coat.

It has long been thought that double merle was the cause of the deafness in the Catahoula; however, numerous double merle breedings have resulted in a complete litter of double merle puppies that were colored and without deafness. This gives way to the thought that the parents were cryptic or near cryptic merles. Could it be that the fearful breeding of double merle is not as dangerous in the Catahoula as it is for other breeds? It appears to be so.

The majority of dark and solid colored Catahoulas are being wrongly identified as non-merle, when in all likelihood the majority of them are single merle. With all the dark and black dogs tested, it appears that when there is white coloration anywhere on the dog other than the chest, it is probably a single merle. This can best be identified in puppies, as the coat may sometime darken and the white will disappear. Dark colored dogs may display their merle coat variance when sunlight is shining on them.

Since 1994 I have been breeding merle to merle as a part of my breeding program. The manner in which I began this program was to study the sire and dam, and the litters in which they belonged. I would also study the grand sire and grand dam and the litters in which they belonged. I found that identifying coat and eye coloration, as well as any physical or medical problems that may have occurred within the litter, gave me a better idea of what may be produced when a pair was bred.

I've asked questions about lineage and litters that some breeders would be very reluctant to answer. I've been sworn to secrecy on some of those answers, and they will remain with me forever, but, if those questions were not asked and answered, I would not have been able to achieve the results that I have.

Keeping records of the breeding and the litters aided in what was working well, and what was not working. By studying those results, it presented a picture of which dogs could or should be bred together. Knowing which dogs to breed resulted in reducing the deafness problem which plagues many kennels. When I first started the merle to merle program, my deafness ratio was about 25%, and still well below the average. It now averages below 4%. It has been reduced simply by studying the litters instead of just choosing a male or female to breed based solely on their colors or attributes alone.

There are many breeders that will tell you to keep away from breeding white dogs, but will purposefully breed for white collars, blazed faces, and white feet, commonly known as Irish spotting. Many dogs that have been identified as double merles have an Irish spotting pattern appearing either in the feet, neck, or face. The piebald gene regulates the merle gene - so while they are related, this does not mean that all Catahoulas actually have the piebald mutation. In fact, it probably shows why the merle gene can create a pattern that appears as piebald. Could it be that breeding for "Irish spotting" in merle dogs is adding to the deafness problem in the Catahoula?

In my first book, printed in 1999, I stated that when breeding merle Catahoulas, light to light should be avoided. Breeding light to medium, light to dark, medium to medium, medium to dark, and dark to dark within merle dogs should produce the better results. Well, after all the testing that has been performed, that statement still holds true.

Now that DNA testing can identify merle and non-merle, it is beneficial to the breeder to have their dogs DNA tested, whenever possible. Knowing that you are about to breed a light colored double merle to a non-merle, which will produce a complete litter of single merle pups, ensures a lesser chance of defective pups being born. Today's breeder has more tools at their disposal than ever before, and those who refuse to use the tools will only be hurting the breed as a whole. (GenMark, the company that was providing the merle DNA testing has been purchased by Idexx. Idexx is not offering the test at this time.)

Below, I have placed a picture of puppies from the same litter in an effort to show that a pup cannot be identified by phenotype. Before going to the answer, study the picture carefully. Examine each of the puppies as closely as a picture will allow, then make your guess which pups you believe would be non-merle, merle, or double merle.

These puppies were DNA tested, so I can assure you that the results are accurate. There are no rewards being given, only a lesson to be learned.