From the (very good) comments:
From Chris: One thing interesting about collies verses their cousins, the shelties, is that for the past 60+ years, blazes in collies have been frowned upon and thus have largely been bred out (or at least minimized to near invisability). The vast majority (90%+) of collies have solid (no blaze) heads. Even the white collies (i.e. color-headed whites, not double dilute whites) tend to have solid colored heads or discreet blazes. Collie breeders just HATE big blazes (I know – I had a blazed collie, my late great Pablo, and at the nationals, some folks recoiled as if he sported a big scar on his head instead of just some white hairs. I kept my eyes open for other “strongly blazed” collies and found 5 others – that year the nationals had a entry of IIRC 800).
I don’t believe the “white-eared mismark is found in collies. I’ve never seen or heard of one in modern times.
I remember an interesting discussion about breeding white shelties and a comment was made that it should be discouraged as it tended to produce deaf dogs. I was surprised as color-headed white collies hear just fine (I’ve had two including my current sable-headed white, Fawkes). My pet theory on why white collies don’t have hearing problems is due to the lack of blazes in the breed. In contrast, blazes are widespread in shelties and so breeding two white factored shelties with blazed faces might well produce pups with excess white on the head and the increase possibility of deafness. My theory may be totally bogus but I like it for now.
Chris – I have definitely noticed the blaze preference. The interviews I’ve seen with the Weatherwax people about choosing the official Lassies (which have never been AKC registered and are hardly show quality, but are purebred) seem to focus entirely on picking the one puppy that has the big fat blaze people think of Lassie having.
I think the science supports you on head white. Breeds with very strong head color can sustain piebaldism for generations upon generations without a lot of color-related deafness; look at the Papillon.
Having said that, deafness has many, MANY causes in dogs, and blaming it only on color leads to lots of (legitimate) objections. Color around and over the ears is a fine rule of thumb, but we shouldn’t automatically think that every white-headed dog is deaf because of lack of color, and we shouldn’t assume that every deaf dog that has head color must somehow have white hair inside the ears or something. For that reason, and because even the whitest of white-spotted breeds doesn’t produce only deaf dogs, I don’t personally like attempts to justify color disqualifications based on deafness; there are too many inconsistencies. I DO think it’s a good idea for breeds who have an existing definition of a spotted color to try to avoid the temptation to go whiter and whiter and whiter. That trend is something you can see in a whole bunch of breeds, because we tend to see whiter dogs as flashier. Encouraging breeders and judges to keep the correctly marked but darker dogs on an even footing with the lighter ones makes sense.
I should also add that I am not sure it makes much sense to treat color-related deafness like it’s a gene. You have recommendations in a bunch of white breeds to not breed unilaterally deaf dogs, because the deafness “may be passed on.” It’s not the deafness that’s being passed along, it’s the COLOR (or lack thereof). You could perfectly responsibly breed a deaf dog as long as the breeding partner had a lot more color, and two hearing dogs can certainly make a bunch of deaf puppies if the parents produce a lot of white. Treating it like it’s a separate gene from the color-related ones doesn’t do the dogs any good because it falsely penalizes (or falsely elevates) breedings that may give you completely different results than the parents show.
From Carolyn: One clarification: “mismark” generally indicates a dog with too much white to be (easily) showable, such as a half-mask or white-headed dog. The Pem and Cardi standards differ: any body white above a horizontal like from the elbow back is a “mismark” on a Pembroke. In Cardigans we generally label this a “splash coat”. Only dogs with over 50% body white are to be faulted. Likewise on the head, white ears are permissible in Cardis but not in Pems.
It has been generally accepted for quite a while that head white and body (excess) white were not related. We had our own early experimentation: our first bitch Julie was a plain male x a white-headed bitch. There were no mismarks in either of the litters they produced. For Julie’s first litter we bred her to a half-mask. Result was 5 normally-marked heads, 2 half-masks, 1 white-headed. We lost an additional normal face, half-mask, and white-head at birth. No extra body-white (piebald/splash coat) on any puppy.
Alice and Hunter obviously each carry both the head-white and the body-white genes.
Boxers and some other breeds have restriction to the piebald gene which mimic Irish spotting. I’m wondering if Irish was completely eliminated from the boxer/Pembroke cross descendants.
Carolyn – What I should have said more clearly in what I wrote earlier is that Little’s divisions of “irish,” “piebald,” and “extreme piebald” aren’t supported by DNA evidence.
Cardigans aren’t actually irish spotted, not as we’ve traditionally defined the term (as being on the “s” locus as a kind of minimal piebaldism), and there aren’t just three types of spotting in the MITF-spotted dogs.
Instead, we need to come up with a new term for herding-spotted (which also may be Bernese spotted and Boston Terrier spotted), and differentiate it from the MITF.
And we need to understand MITF better; one study I looked at thought that MITF actually encompasses a huge spectrum of color, from very minimal white to entirely white, depending on how many copies of the mutation were being passed along. This would make sense when you look at spotted breeds.
If this is in fact the case, one scenario that would make sense is that in Bull Terriers and Boxers and Danes, what’s been trapped in the breed is the ends of the spectrum and nothing in the middle. So you have, for example, 2 copies of the mutation (plain dogs) and 20 copies of the mutation (white dogs). When bred together they balance and create a dog with medium white (the flashy or mantle-marked dogs). You can’t make the medium white “stick” because the components are 2 and 20.
In terms of how Cardigan mismarks work, we do now have a good idea how piebald Cardigans end up in litters (both parents have a copy of MITF with some number of mutations). We don’t know how the head mismarks work. As of yet, we don’t have any evidence for a half-mask or white-head gene within the herding spotted gene, because we have no idea even what the herding spotted gene is. Even the fact that I’m calling it herding spotted is my own invention and I’d have to be very ready to abandon it. Breeding-based evidence is not a bad thing, but (as we find with a whole bunch of Little’s stuff) it often bows in the end to different data once the genetic basis is discovered.
We also have to learn which color characteristics are not genetic – we know that some are developmental and are not the result of genes, at least in cats (cloned cats can be different colors and have different eye colors from the original cat). White chest spots in solid breeds are probably the result of this kind of random developmental event.
As an example of this phenomenon, Dalmatians as a breed have a big problem with uric acid; they have a gene that prevents them from breaking it down and excreting it. Dalmatians have been bred to Pointers to attempt to create Dalmatians with normal uric acid metabolism. This experiment has been a resounding success in terms of cutting the rate of the bad uric acid mutation, and the “new” Dalmatians with some Pointer blood look like perfectly normal Dals and are of high quality in all respects. All, that is, except for the sacred spots. Dalmatians with normal uric acid production have smaller spots than the Dals with high uric acid. The low-acid dogs don’t have the half-dollar-sized perfectly round spots that are the holy grail of Dalmatian color; they’re more dime-sized. You can see this beautifully illustrated in the “I” litter here. So what’s going on? Is the uric acid gene also a pigment-controlling gene? Or does a higher concentration of uric acid in the dog lead to larger spots? Can breeders push the low uric acid dogs to have larger spotting without abandoning the positive health effects?
All of these questions (Dals, Cardi heads, etc.) are COMPLETELY open at this point in time. We just don’t know how it works, and the genetic research has shown that the picture is actually incredibly complex. What I find just riveting about this kind of stuff is that it turns out that so many different gene mutations can cause the exact same changes in appearance. Who knows how many different mutations we’ll eventually find leading to white spotting and other colors, some of them isolated in just one breed and some widespread.
Oh, and I have no idea whether the Cattenach (Steynmere) dogs have retained a more stable white spotting pattern than their cousins. I’ve been following his dogs for years, but he doesn’t usually post pictures of whole litters so I can’t tell what the spotting has done. I know he does have white dogs.