This post first appeared on August 7, 2012
One of the most interesting aspects of white patterns, at least for an artist, is whether or not they overlap one another or interact with each other (and other modifiers). Perhaps because most techniques involve adding – or sometimes removing – layers of color, it is only natural that artists tend to assume a layering relationship. What is appears to be true is that patterns typically have a complex set of interactions. For example, there is good reason to believe that some of the sabino patterns (like the one seen on the horse above) interact with whatever mechanism produces ordinary white markings by amplifying the white in those areas. Meanwhile both the markings and the sabino patterns appear to interact with the base color.
Simple layering seems to be far less common. That is one reason why some forms of snowflaking (like the one in this post from a few days ago) are so interesting, because it appears that some types do overlap existing patterns. I suspect that overlapping white spots are behind the really unusual “jigsaw” leopard Appaloosa mare Dazzling Vision Spot. More common, though, are overlapping dark spots on the face. In dogs these are sometimes called Blenheim spots, for the red and white pattern in Cavalier King Charles Spaniels where the markings are considered desirable. One is visible inside the blaze of the red and white spaniel in this nineteenth-century copy of a Landseer painting.
The horse at the top of the post has a similar spot in the top corner of his blaze. In horses these inset spots more often appear offset rather than centered on the blaze. This can give the the top of the blaze a scalloped look. Since the one in the picture is set a little further inside, it bisects the blaze so that there appears to be an irregular section of disconnected white. That white is probably not a separate marking, but rather the remainder of the blaze that the overlapping colored spot did not cover. The tinted areas in this photo show how this works.
I have shaded this Paint Horse’s broad blaze blue, and the imagined overlapping spot bright pink. The area where the colored spot overlaps the blaze is purple. On this horse, the disconnected white this leaves is much smaller. I have called these colored patches occluding spots, since they cover (occlude) part of the white face markings. If the spot is large enough, the result is what is often called a badger face.
Some badger-faced horses have spots large enough that the only thing left of the blaze are small, detached segments of white. Here are some good examples of that: Akhal-Teke1, Akhal-Teke2, Thoroughbred and a Paint.
I suspect that the horses pictured so far have something similar going on with their face markings, with just slight variations in scale and placement. I do not believe every dark spot inside a face marking is an occluding spot (or minimized badger-face marking, if you prefer). This guy is perhaps a good horse to look at what are probably two different things altering his face marking.
The most obvious change to his blaze is what looks like two or more occluding spots breaking it into two pieces. If you look further down his face, though, his blaze begins to break apart into round spots right behind his nostril. Because the scale and character are rather different, it is my suspicion that there are different causes for the two changes. What is happening close to his nose looks a bit like the way sabino degrades the edges of markings. This Belgian has a more roany version of what is probably the same type of thing.
Here is another horse that has what I think are two different things going on as well. Along the upper edge of her blaze a mid-sized occluding spot has cut off most (but not all) of the corner of her white marking.
Then there are small spots of color inside her blaze. I suspect that is Belton patterning. Since first posting about the possibility of dark ticking separate from the actions of the different patterns, many readers have sent leads on horses with this. That will be the subject of the next post. (Previous posts on Belton patterning, for those missed them, can be found here, here and here.)