Overlapping and Interacting

RomeoMarkings

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.

LandseerCopy

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.

occludespot2

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.

Badger

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, Paint Horse, Thoroughbred and another Paint.

The separate nature of occluding spots is even more apparent when they occur when white patterning has completely removed the color from the face: Paint, Gypsy Horse, and another 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.

BrokenBlaze

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.

Lazy5Belgian2

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.

BeltonandOclud

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.)

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10 Responses to Overlapping and Interacting

  1. Joanne Abramson August 7, 2012 at 10:34 am #

    I would love you to address the split faced horses in this blog as well. We have several that have a dark side and a white side where the patterns were obviously fighting with each other.

    • The Equine Tapestry August 9, 2012 at 7:38 am #

      Can you link to pictures, Joanne? Do you mean the type of pinto markings where they have a colored patch on one side, but none on the other?

      • Joanne Abramson August 9, 2012 at 12:42 pm #

        Yes, where half of the face is tobiano, and half is frame or splashed white.

  2. dakota328 August 15, 2012 at 11:29 am #

    I realize the content of the joke is rather immature however, the horse on the right seems to have the same overlapping as talked about in this post.
    http://chzmemebase.files.wordpress.com/2012/08/eslcway83k6otfli5useqg2.jpg

  3. Leanne B September 8, 2012 at 8:03 am #

    I’m not sure if my Welsh Cob (Sec. D) mare would count as a split faced horse, but I have always been interested in her ‘harlequin’ stripe where half of her face looks solid and the other side looks ‘smudged’. She is a dark bay mare and appart from her star/stripe/snip, she has no other white markings. We think she exhibits pangare as she has light hair around her eyes, muzzle flanks, throat and chest, behind her elbows and on her belly and backside etc.

    https://fbcdn-sphotos-f-a.akamaihd.net/hphotos-ak-snc7/408278_418809398155573_1260351208_n.jpg

    https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-snc7/402933_418809368155576_1758380436_n.jpg

  4. Caitlin September 24, 2012 at 2:25 pm #

    I am so glad to be able to leave a comment that brings something to the table! This tendency of mammals to have pigmented areas on the forehead while the surrounding skin is unpigmented is, I think, easily explained.

    As you know, whether or not skin/hair is pigmented is determined most often by whether or not melanoblasts – early melanocytes or pigment cells – have been able to make their way into the skin. This process is carefully timed and occurs during embryonic development; if the melanoblasts do not reach their destinations in time, they miss their chance, and the skin continues to develop without them. The destinations most likely to miss out are the feet, the dorsal aspect of the trunk, and the center of the face. Since we know that this is a timing issue, and that those are the places that are most often missed, we can assume – though you don’t have to – that these places take the longest for the melanoblasts to reach and are furthest from their point of origin. So it seems like they’re coming from the top, down. This link: http://www.stembook.org/node/581#sec2-2 …covers what I am describing. I like to visualize this process as a bunch of cars racing for parking spaces in a limited period of time.

    What is the point of origin? The top of the organism. Melanoblasts come from the neural crest, but the starting line for the cars in our race isn’t straight across. It turns out that first, melanoblasts “pool” in certain regions. They hang out there, dividing and proliferating, before dispersing. This link: http://www.informatics.jax.org/wksilvers/frames/frame9-1.shtml …discusses what I am describing, and if you look at the figure, there is a helpful drawing. I wasn’t able to find an image that indicated where these melanoblast pools are, though I would have found it useful. You’ll notice that there are several pools on the head.

    So now we have our cars revving at several different starting points, and the question becomes, is it a free-for-all where any car can take any space, or are there a set number of spaces for each pool? It turns out that there’s a bit of both: http://dev.biologists.org/content/129/14/3349.long In the trunk, it’s a bit of a free-for-all, which suggests an explanation for bodies and haunches of horses with KIT mutations to be roaned or mottled (getting a bit tired so you’ll forgive me for not explaining further.)

    And what about those unusual, reoccurring pigmented dots on the foreheads of mammals? This population of cells corresponds to a distinct pool of melanoblasts, which never have far to travel before their time is up. Even if those migrating from another pool fail to close the gap across the face, it is possible for this pool on the forehead to be unaffected.

  5. Loghan December 12, 2013 at 11:02 pm #

    Not sure if this is still an active page or not, but I’ll give it a try…. I was wondering if occluding spots are a solid indicator of sabino, or can they occur in any solid horse color as well? All of the examples you showed seemed to be sabino horses, so do the markings only occur in sabinos?

    • equinetapestry December 16, 2013 at 11:06 pm #

      Hello Loghan! Yes, the site is once again active, after several months were I was on hiatus while I worked on the upcoming book. And the whole topic of markings and how to classify them using older terms (like sabino) is undergoing a lot of rethinking right now. I hope you can join us over the next few weeks, since that’s going to be the subject for a number of upcoming blog posts.

  6. Kristina Pry December 27, 2013 at 7:26 am #

    I have noticed many Tekes have white facial markings that seem truncated. Are there some breeds that exhibit it more often than others?

    • equinetapestry December 28, 2013 at 3:03 pm #

      Tekes are one of the breeds where the markings are unbalanced. That is, in most breeds the white on the legs tends to correlate with the white on the face, so that high white legs are usually paired with a fair bit of white on the face. In Tekes that connection seems less true, so that you get high white legs with relatively little face white more often. This is also true for Hackneys. I suspect, given the findings in the most recent paper, that we’ll find that the Tekes have markings that are more often MITF-based marking mutations, as opposed to KIT mutations. That might explain why blue eyes are surprisingly common in Tekes, too. But that’s something I’ll be writing about as I get to the new study. :)