First of all, a couple of people have written to shed some light on the dog in the photo that appeared in the previous post. Apparently it is from a breeding of a Weimaraner and a GSP that has some Weim blood. So that would explain the grey color; both parents were able to transmit the dilution factor to the pup. And that seems to confirm the idea that you simply cannot get the dilute grey color in any first generation cross to a Weim. The recessive dilution factor has to be found on both sides of the pedigree.

But I also received reports from other folks telling me about white Weims in the US and in Germany. In the US, they are called "piebald" and there are reports of entire litters having the same sort of white and grey coat and even some grey "ticking" on the white background color. I am not sure what the Germans call them, but as indicated in the previous post, they would not be allowed to breed even when they come from pure grey parents.

And it turns out that DNA tests have been indeed indicated that some of the dogs in the US and in Germany are in fact from the all-grey purebred parents listed on the pedigree.

Of course, that does not eliminated the possibility of cross breeding further back in the family tree. It only proves that the parents are who the breeder says they are. Cross breeding may have happened further back, perhaps in the grandparents' generation or great grandparents' generation. And it could have happened even further back, so far back that it could be a case of atavism.

Atavism is a biological tendency for organisms to revert to an ancestral type or to suddenly manifest traits have not been seen in many generations. In humans there are cases of babies being born with vestigial tails or with larger than normal canine teeth. Horses can sometimes have extra toes and there have been cases of dolphins and whales with vestigial hind legs.

And there are a number of things that can cause atavism. Genetic mutations may trigger traits that have been dormant in the DNA for many generations, to suddenly re-appear. A significant change in the timeline of fetal development can also lead to atavistic traits; if the development period is cut short or goes on too long, atavism can occur.

No one knows the exact makeup of the Weimaraner. There are many theories about how it came to be and I explore some of them  here and here. But no matter what the exact recipe was, I think everyone agrees that at some point in time, Pointers and Setters must have been included in the list of ingredients. So maybe the white comes from way back in the early days when the breed was first being created.

So what exactly are we seeing when we see a white Weim?  Is it the result of some shady cross breedings in the recent past? Is it a fluke of nature; the result of a viral illness during gestation? Or is it a throwback to the very beginnings of the breed?

My guess is: "all of the above".  I believe that there has been some cross breeding done in the last 40 years and breeders certainly cross bred to create the breed in the late 1800s. But given the huge numbers of Weims born every year -- more than 20 thousand pups per year world wide -- the chances of other more 'fluke of nature' causes are probably high enough to explain at least some of the white Weims out there.

And it turns out that white coat issues don't just apply to Weims. In response to my last blog post, a friendly reader sent me a link to a very interesting and article about white in another self-colored gundog breed, the Vizsla.  It is called "Understanding White" and it was published in the Vizsla Canada Newsletter, Vol.7, No.4, September/October 2001. Here are a couple of passages that are about Viszlas but could just as easily be about Weimaraners:

When discussing white, it is important to keep in mind that the presence and extent of white markings are not entirely under genetic control. As early as 1957, referring to experiments done by Sewall Wright nearly four decades earlier, Clarence Little cautioned that: “an appreciable amount of  variation in the extent of body-surface pigmentation is usually non-genetic in nature.” Without discounting the primary role of genes, it seems reasonable to think that various factors other than genetic can influence the distribution of pigmentation cells or perhaps, even interrupt it at times. We know that some factors may delay the normal pigmentation process as happened with the puppy mentioned earlier and there will no doubt be cases where the process is not only delayed but interrupted altogether. These factors could be anything from environmental to nutritional. 

Being aware of (this) might assist in avoiding hasty conclusions about the parentage of some Vizslas, often from field bred strains, that exhibit a considerable amount of white. In those cases, casual observers are sometimes quick to conclude that a dog is of impure breeding and whispered accusations of crossbreeding to Pointers follow suit. Such breedings, accidental or deliberate, may indeed have taken place but we should always keep in mind that dogs with considerable amounts of white might also be produced from the breeding of two purebred Vizslas.

Breeders whose primary selection criterion is field performance may not select against white... as rigorously as breeders whose primary focus is the show bench or may not select against it at all. If selection against (white) is not a priority with a particular breeder, it can be expected that this breeder may produce more dogs with white markings and with larger white markings than a breeder who makes selection against white markings a priority.  It would be my suggestion that not a few cases of rumoured crossbreeding simply involve a purebred Vizsla...