All theory, dear friend, is gray, but the golden tree of life springs ever green.
Johann Wolfgang von Goethe

The Weimaraner has a unique grey coat inherited from the Grey Dogs of King Louis. Right?

Wrong.

The Weim's coat is not grey, it is not unique, and it didn't come from any 'Grey Dogs of King Louis'.

OK, I can practically hear the bloomers bunching up right now and you are probably doing this:

The Weimaraner's coat is not grey. It is brown. However, a mutation in the MLPH (Melanophilin) gene causes an uneven distribution of the brown pigment that leads to the formation of large granules (macromelanosomes) in the hair follicles and shafts. So instead of looking similar to a solid brown GSP type coat, the Weim coat appears as a 'diluted' brown which Weim folks call "grey" or "silver-grey". If a dog with a black coat has the same mutation, the uneven distribution of pigment leads to a similarly diluted appearance. In Weim circles, dilute black is called 'blue'.

Long answer: While it is possible that a spontaneous mutation occurred in hunting dogs in the area around Weimar sometime in the mid to late 1800s, it is far more likely that a mutation occurred centuries before the Weim was even on the drawing board and was then brought in by one or more of the types of dogs used to create the Weimarner in the mid 1800s. But what kinds of dogs could have brought it in ?

One of the most oft repeated theories is that it came from the Chiens Gris (grey dogs) of Saint Louis of France. But as I explained in a previous post, King Louis’ dogs weren't actually grey. They were tri-colour black, brown and red.

Saint Louis' Chiens Gris (grey dogs)

Another theory is that the grey came from crossing a "lemon" (orange and white) Pointer bitch to an old style German "Leithund" (tracking dog). However, the lighter pigment in lemon Pointers is caused by a mutation in the the MC1R gene, not the MLPH gene. Could the dilution mutation come from the Leithund? Maybe, but we don't really know what color the old Leithunds were and none of the old literature says anything about 'grey' ones. The closest thing we have to Liethunds today are breeds like the Bayerischer Gebirgsschweißhund (Bavarian Mountain Hound), and they are a reddish brown color.

Bavarian Mountain Hound

Lemon Pointer

So what we need to find is a breed or type of dog that a) had a grey coat, b) was relatively common in the area around Weimar before the 1800s and c) was owned by people ready and able to undertake a breeding program that could eventually lead to a new 'pure' breed of hunting dog.

If you read the old literature and look at old paintings and sculptures, one breed stands out. It had a grey coat, it was relatively common in Germany and elsewhere in Europe in the 1800s and it was popular among the nobility. The breed is the Italian Greyhound.

A reenactor as Frederick the Great with two grey Italian Greyhounds

Now that is not to say that the Italian Greyhound was specifically used in the creation of the Weimaraner as a hunting dog. But at a time when 'pure' breeds of dogs did not really exist and cross breeding was widely practiced, it is entirely possible that somehow, the dilution gene that was already in the Italian Greyhound somehow made its way into the dogs that were eventually used to create the Weim. After all, in an article entitled One coat color — one breed? Wanda M. Gerding & Jörg T. Epplen, Human Genetics, Ruhr-University Bochum, German state that "...the b-gene version  found in the Italian Greyhound is virtually identical to one of the three b-alleles found in the Weimaraner".

Italian Greyhounds were also relatively popular in Germany just before the development of the Weim and among people who had the means to undertake a breeding program. The Italian Greyhound was in fact the favorite dog of Germany's Frederick the Great (1712 – 1786). However, Frederick the Great was not a hunter, but actually one of the earliest supporters of animal rights. So he was probably not involved in any efforts to create a new breed of gundog. But other nobles in Germany who had Italian Greyhounds and enjoyed hunting may have been. Could their dogs have been the source of the dilution gene that made its way into Weim lines?

Could it have even been the dogs owned by good old Grand Duke Karl August? He was a great hunter, he had the ways and means of keeping many dogs of all types in his kennels and there are several works of art showing him with what are obviously greyhounds. And he is the guy that is usually credited with creating the Weim.

So maybe the real story is that the Grand Duke didn't actually create the Weim (as I speculate here) but somehow, his dogs managed to contribute a dilution gene to the ancestors of the Weim back when cross breeding and uncontrolled breeding was practiced just about everywhere.

Grand Duke Karl August with Corena Schroeter, Goethe and two Greyhounds