I love merle. Want to say that right off the bat, so no one will think I'm bashing blue dogs or red dogs or Aussies or Catahoulas or any other merle-colored dog. Check out this handsome Catahoula:
Merle is a striking color, no question. But what's up with all the blue merle border collie puppies?
Merle has never been common among working border collies: great working merles are rare as hens' teeth. I'm no geneticist, but it's my understanding that a merle pup can only be produced if one of the parents is merle --- the last thing a breeder of good working stockdogs is going to care about. It doesn't help that breeding for merle carries a certain amount of risk, as in, you can kill some of the puppies now, or you can kill them later. Quoting from the GenMARK site:
Both heterozygous merle (Mm) and homozygous double merle (MM) dogs may exhibit auditory and ophthalmic abnormalities including mild to severe deafness, increased intraocular pressure, ametropia, microphthalmia and colobomas. The double merle genotype may also be associated with abnormalities of skeletal, cardiac and reproductive systems.Genetic testing for merle is now available through GenMark. More information on the recent discovery of the merle locus can be found here and here, with illustrations here.
ADCH MACH-4 Marshland Fantom of the Opera TD PT ("Heather"), 2-time AKC National agility champion, member World Champion small-dog team, owned by Kathie Leggett.
Homozygous merle puppy with microopthalmia (small eyes). More photos at the Aussie Eye Defects site.
Responsible breeders of companion dogs like the beautiful Sheltie above will be all about the merle test. Puppy millers, not so much. This gent was expelled from the American Border Collie Association in 2004. He appears to be breeding and selling merles. God
help us bless America.
There is a smart thread on merles on the Working Stockdog Forum [where the breeder in question actually makes a rather telling appearance].
And over on the Border Collie Boards there is an excellent thread on the "merle explosion." Good links in that thread, too, and I've swiped some for this post. [While you're on the Boards, take a look at the "Ask an Expert" section -- top handler Bev Lambert is the current expert. You can watch Bev's great bitch Pippa by clicking on the first StilHope video in this blog's sidebar.]
Repeating a line from the GenMARK site: "Both heterozygous merle (Mm) and homozygous double merle (MM) dogs may exhibit auditory and ophthalmic abnormalities." Breeding merles isn't for the faint of heart, and the designer-color craze, though it may be a windfall for puppy millers, is very bad for border collies.