Yesterday, I shared some information on Carlton the puppy’s “weird eyes.” Today I’d like to document some of the things I learned about how he got to be “the world’s whitest dog.” (And, FYI he weighs 31 pounds now, which makes me think he will probably end up the size of his companions Brody and Harvey, though perhaps less bulky.)
I think that he has a whammo combination of THREE genes that make him pale. I learned a lot, thanks to a great collection of information on dog color genetics by Jess Chappell for a lot of this, along with the doggie eye problem reading I did from the veterinary opthalmomogist’s textbook (see references).
Carlton is not an albino
Nope, he is not an albino. Albinism is not found often in dogs like it is in bunnies, rats, and humans. There are a LOT of genes that can make a dog white, though. I won’t go into detail (you can read it in the links below), but I’ll share some ideas.
Is he a double merle?
At least two veterinarians who have examined Carlton have posited that his coloring is due to being a double merle. What’s that, you ask?
First, merle is a beautiful pattern that occurs in a number of dog breeds (I list some at the end of this article). The base color of the coat is beautifully dappled, and people like it a lot. It will show up if just one parent has the gene (it’s dominant).
However, when two dogs with the merle gene breed, it’s not more of a good thing. It can be quite bad (in fact, a horse with two copies of the similar gene will be a “lethal white” and be unable to defecate, so horse breeders are very careful with their paints). In dogs, it can lead to GET THIS eye deformities and ear deformities, if the ears are white.
The reason that the vets say Carlton is a double merle is not his coat color, but the issues that have arisen in his eyes. Some double merle dogs have tiny, malformed eyes that must be removed, or are completely blind, so Carlton is lucky that he has milder symptoms.
Still, he doesn’t LOOK like most dog breeds with merle in them. And since he doesn’t have the collie issues in his eyes, even that possibility is remote. I guess a Great Dane could have gotten to his very small mother, but I doubt it.
We will just have to do DNA testing to see what kind of merle carrier is lurking in his very, very mutt background.
There may be some extreme white in there
Carlton also shows the characteristics of the extreme white spot pattern. Chapell says:
The extreme white pattern consists of a completely or predominantly white dog with just small amounts of colour on its head and sometimes base of tail. Small body patches may be present too. Sometimes the nose is pink or partly pink, and the eyes may be blue in some breeds due to lack of pigment.
Hey, that sounds like my boy. It’s apparently caused by being homozygous for the piebald gene, probably combined with something else.
This pattern is found in the kind of terriers that we were told his mother is (Jack Russell, or something). It’s also found in the kinds of pit mixes we see all over this part of Texas. If you ask me, this alone might explain his coloring, but the vets seem pretty convinced there is merle in there, too.
Don’t forget the cream!
I’m confident (and his regular vet backed this up) that he has cream dilution in addition to merle and intense white genes. That’s why his spotting, which is the common type for extreme white dogs, is so pale. In fact, you can hardly see the pale cream coloring on his ears. It’s good that he does have it, because even diluted, a colored ear means the ear canal will develop properly, so he can hear.
If his father is indeed part “pit” (American Staffordshire mix), the dilution would most likely come from there. That makes for a very pale dog.
Anyway, so now we know why Carlton is so white and why his eyes are weird. We do NOT know what breeds in his background made him this way, which makes me really want to do a doggie DNA test, like I said above.
The good news is he is a functional dog, not deaf, and not blind. We will check back in three months to see if his cataract is growing or not, but otherwise, he will just live with weird eyes. If the cataract is not growing, he will need to be seen yearly.
One other good thing is that maybe as he grows his retina will smooth out. Especially if he turns out to be part Great Dane. I think one giant dog per household is plenty, though.
Merle gene carrying dog breeds:
Catahoula Leopard Dog
Old English Sheepdog
Cardigan Welsh Corgi
Collie (Rough and Smooth)
Dachshund (known as dapple)
Allen, Meredith, March 2018. “How Common Are Albino Dogs?” Pet Care Rx. https://www.petcarerx.com/article/how-common-are-albino-dogs/1696
Chapell, Jess, 2018: Dog Coat Color Genetics, http://www.doggenetics.co.uk/index.htm
Gelat, Gilger, and Kern, 2014: Veterinary Opthalmology, Volume 2, 5th ed., pp. 1311-1316.
Rich, Sandra Dee, July 2018, Facebook post, Cameron Texas.
Yu-Speight, Audrey, July 10, 2018: Diagnosis and Comments, Veterinary Eye Center, Austin, TX.