Circling back to the weird stuff

This is kind of a catch-all post.  There are lots and lots of things about horse color that we still don't know what's creating them and why, so it's hard to categorize!

Dun
I did end up going back to do a little research on the dun/non-dun thing I talked about briefly. And it turns out?  It's not that funky after all.

Basically, what they've determined is that dun seems to have two versions.  One version is traditional dun: diluted body, dorsal stripe, primitive markings.  That's still marked as D in genetic testing.

The second version is just the primitive markings and dorsal stripe, without the dilution to the rest of the color.  It sounds, reading between some lines, like this might be the cause of the countershading that makes people think they must have a dun when they don't.  That's nd1.

And "off" - no dun, no primitive markings - is now nd2.

Examples of the three genes from the original paper.

They've also determined an order of how these get applied.  D and nd1 seem to be dominant, but something has to take the lead, right?  It goes nd2 => nd1 => D.  So if you've got a horse that's nd1D or nd2D, they're dun.  If you've got a horse that's nd1nd2, they've got primitive markings.  Neat!

Examples of non-dun 1 combinations, from the original paper.

Sooty
I kind of blew past sooty when talking about coat colors, because it's definitely one of those nebulous things.  They've done some research on it, but haven't discovered what actually causes the effect yet.  One piece - a German study on some Franches-Montangnes horses - suggests that whatever this sooty/darkening gene is, it may be recessive rather than dominant.  (I'd link the article, but - German.  I'm all for useful links, but not if I don't know what it actually says!)

Sooty as a concept describes a horse whose coat is generally darker along the back and spine, and who may have a darker area on the face almost like a mask.  It tends to produce dapples.  It might also produce countershading, but given the nd1 - well, who knows right now.

Example from Wikipedia.

But, just to make things more exciting, sometimes sooty works from the hooves up.  Not every sooty horse has dapples.  There's even a floating theory that sooty - which isn't generally uniform - might be at least partly responsible for liver chestnut.

Sooty tends to have a striking effect on buckskins (as the photo above) and palominos, but it can show up on pretty much anything except black.

Pangare
Pangare is the other one I kind of blew past.  It's also sometimes called mealy - as in, mealy muzzle.  Horses with pangare will have lighter color around the muzzle and belly; the light color can extend up into the flank and behind the elbows, and sometimes up the throat.  Some horses even show lighter color around their eyes.  What "light" means depends on the horse; it ranges from off-white to light tan, generally.

Pangare only seems to show up on chestnuts and bays.  Blacks don't how it at all except when they're foals, and that's only on some and only until the foal coat sheds.

Haflingers.  PERFECT example of pangare - seriously, just google Halflinger horse.  Photo from Wikipedia.

Again, it's not something they've determined what the heck causes it.  Unlike sooty, they don't even have the most basic of studies to suggest a sort of maybe way it might be inherited.  It's just a thing that happens, and it shows up in some breeds more than others.  Halflingers, Belgians, Fjords, and Exmoor Ponies can all show up with it.  It's actually thought that it may be something present in pre-domesticated horses, as it shows up in the Przewalski's as a general rule - and in a lot of the non-horse, non-zebra equines as well.

This page has a gallery of some absolutely stunning images.  I wouldn't turn down that draft-Fjord cross... lol

Flaxen
And the third really common one that nobody's cracked the genes on is flaxen.  They know that something causes manes and tails on chestnut horses to lighten.  How much lightening varies - it can range from barely flaxen to the obvious blonde color to near-white.

Like momma here.

Current theory is that it's a family of genes, since it's definitely an inheritable thing.  The first look at the issue (a study done on Morgans) suggested a recessive inheritance pattern to basic flaxen, but two barely-flaxen parents can (but may not always) produce horses with near-white manes and tails, so clearly something else is going on too. 

Gulastra Plume
Also known as silvertail, this is when an otherwise dark bay horse turns up with a non-black tail.  I say non-black - descriptions and photos range from silvery black to actually white.

Donatello, borrowed from White Horse Productions' page.

The name "Gulastra plume" comes from the Arabian folks.  A chestnut stallion named Gulastra threw these pale tails over and over again on his bay foals, although he himself didn't actually show it.  It's not limited to Arabians, though; it can crop up in Thoroughbreds (as with the image above), in miniatures, and anything in between (or bigger).

Looking at available images, it tends to whiten from the tip up, and it tends to blend together in a way that's unlike silver.  Equine Tapestry notes that she sees it a lot in wild bays, and that although it looks like the rest of the horse is unaffected, it's not unusual to see a sprinkling of lighter hairs in the mane and silvery heels (if there are no interfering white markings).  She also points out, though, that "wild bay" isn't strictly defined, because it's a term for how the horse looks and not a true gene, and that the silvery tail isn't restricted to that appearance.

So what is it?  Nobody knows.  Early theories speculated it was rabicano, but rabicano puts in white from the top.  It could be related to wild bay; it could also be a sabino or sabino-like pattern, which is what the Morgan folks seem to think.  It's not sabino-1, though; Gulastra plume Arabians have been tested for that and came up clear of that gene.  It kind of resembles splash, in that it's coming up from below, but isn't necessarily linked with the kinds of other white markings you typically see in splash.

Birdcatcher, Chubari, and Bend Or spots
These spots are another small genetic mystery.

Birdcatcher spots are small white spots - usually smaller than 1 inch - that randomly appear (and sometimes disappear) on a horse's coat.  They often show up later in life, and may have roaning to them; in fact, the horse may also have a very small amount of roaning around the flank and tail.  It's more common to see them on chestnuts, but they can and do appear on any color.

Example from Equus Magazine.

The name comes from an Irish-born Thoroughbred in the 1800s named Birdcatcher.  How it gets passed on - or if it does - is still a mystery.  Some believe it gets passed on along family lines, but others think the marks are just white hair growing in from some injury.  Equine Tapestry thinks it's a combination of both (and totally follow that link; it's got some cool stories in the comments), but nobody's done any research, so it's hard to tell! 

Chubari spots are also sometimes known as Tetrarch spots, after The Tetrarch, a grey Thoroughbred born in 1911.  (Some neat info on him here.)

The Tetrarch, from White Horse Productions' page.

Like the birdcatcher spots, these are also white - but they're much bigger, tending to run more to the egg-sized and -shaped range.  Unlike birdcatcher spots, they seem to only appear on grey horses.  Unlike the weird dappling that grey can show, they only disappear when the horse has greyed out completely.  The Tetrarch is unusual because he has so many; it's much more common to see only a few.

Again, there hasn't been any sort of study on chubari spots.  We know The Tetrarch passed his spots on to some of his foals, and many TBs and horses with TBs in their breeding that show up with chubari spots will trace back to The Tetrarch somehow - but it's not limited to Thoroughbreds, either, as far as anyone knows.

Bend Or spots, unlike the other two, are dark spots - ranging from slightly darker than coat color through to almost black.  They tend to show up on red-based horses more often than bay or black, but have been known to show up on bays as well.  Like chubari spots, they tend to be on the larger side and tend to just kind of stick around once they show up.  (Interestingly, The Tetrarch is said to have shown chubari spots before he really started greying out.)

Example from Wikipedia - enlarge and look at his flank and gaskin.

The name comes from an English Thoroughbred stallion named Bend Or, born in 1877, but the spotting likely comes from one of his ancestors.  The Thoroughbred Heritage site notes that his ancestors Pantaloon (born 1824) and Comus (born 1809) both show the same spotting. Bend Or's grandson Man O'War was said to have Bend Or spots too, but I have yet to find a picture that shows one - both because most of them are in black and white or tiny and because it seems like people only took photos of his left side!

Again, we can see that there's a tendency to pass it down, but nobody knows what's causing it.

Bloody Shoulder
"Bloody shoulder" refers to an area of not-grey on a grey horse.  Even as the horse turns gradually whiter, these areas will stay dark - and the dark area may actually grow after the horse whitens out.

Charmander, TB mare.  From White Horse Productions.

It's not limited to the shoulder, although that's a common presentation.  It's also most commonly found in Arabians, although a few Thoroughbreds have shown up with it as well (not surprising, considering the Arabians way back in the family tree there).

An Arabian example - Sweet Meadows Sanaya

And again we have something that's happening that it isn't clear what caused it.  Some speculation is that it's a chimeric mutation - that the horse had a non-grey twin that was absorbed.  Whatever causes it, it's striking!

The many shades of chestnut
Chestnut's a pretty basic color, right?  I mean, sure, you've got your liver chestnuts, but red is red.

From The Equinest

Yeah, about that.

Borrowed from Equine Tapestry, but viewable many other places as well.

That's a Black Forest Horse, and you'd think that's a silver black, right?  Nope.  They did a study on all of the stallions standing at stud at the time, and every last one of them was genetically chestnut.

And then there's sorrel.  Sorrel cracks me up, because it's a very Western-riding-world term that basically just means chestnut.  Even AQHA will accept either.  That said, I know I have a very specific idea in my head of what gets called sorrel.  Maybe I'm weird?

Brindle
Brindle is a really weird one.  There are two types of brindle.

One is not inheritable.  It's just a random chimeric mutation - normal mom, normal dad, hello random stripey baby.  Usually the stripes are dark, but White Horse Productions has images of some awesome white-striped brindles, including the stallion Catch a Bird, who sired some roan foals when roan wasn't previously known to happen in TBs.

On the other hand, there apparently now really is an inheritable brindle pattern?  Most of the information I'm seeing comes from just one site, Justa Brindle Horse Farms.  She's got some cool examples and she's got some examples that I mostly just frowned at and scrolled on past because I couldn't see much.  It seems like this stripey pattern is coming from a mare called Ima Star Moon Bar, and it's got some seasonal variation that means it's not always that visible.  I'm not seeing much of anything outside of that one site, so YMMV.

Other dilutions?
In Shetlands and Halflingers (and maybe a QH or two), there's a color called "mushroom."  It visually looks a bit like silver black, but the Shetland examples that were first tested tested not only don't have silver - they're actually chestnuts.  They're typically born a pale beige with a pinkish or greyish tint and generally retain that color into adulthood, although some darken.  It's believed to be recessive, although nobody's figured out what gene is causing it yet.  I couldn't find any good not-on-Pinterest, clearly-marked-with-a-copyright pictures that I felt good about borrowing and the ones on Wikipedia are odd, but it looks like the definitive resource for Shetlands is this page from Kellas Stud in the UK, which has some great pictures.

Morgans have what's looking like it might be a new dilute gene, described here.  It's been described as "light black," since it affects primarily black hair (instead of red) and seems to turn genetically black horses brown.  It also seems to be recessive.  There's a similar "light black" that's been found in a pair of Arabians (Mireyenion Tos and Ali-Zeus), a Friesian (Nico), and an Australian Quarter Pony (Mia).  The ones that have been genetically tested have tested negative for all known dilutions, per Equine Tapestry and some of the other links. 

Other Oddities
W21 looks like it might be coming from Icelandics again, with another sabino-type pattern and possibly blue eyes. 

There are two other horses that have tested as genetically buckskin, but look more like double-creams (or cream/pearl).

And I'm sure there's lots more that I haven't turned up with a quick googling!



Additional resources
I'm definitely not the expert on horse color genetics!  I rely a lot on information from the following places:
The Appaloosa Project
Equine Tapestry
New Dilutions

But I've also got some books lying around too.  :) 

• The definitive book is really D. Phillip Sponenberg's Equine Color Genetics (Amazon link to the latest version, but mine is an older version simply called Horse Color) - but I have to say, if you don't understand a little about genetics, it's an overwhelming amount of information that's hard to follow and digest and a bunch of neat pictures.
• Horse Color Explained (Amazon link) is a little bit dated these days, but it's very good at breaking things down into manageable, understandable, at-a-glance chunks.
• Equine Tapestry has two books out: the older The Equine Tapestry: Volume 1 - Coaching and Draft Breeds (Amazon link) and the newer The Equine Tapestry: An Introduction to Colors and Patterns (Amazon link).  I've got the first, but not the second.  The writing style is very similar to what you see on her blog - readable, thoughtful, not too deep into the genetics except as needed to explain basic concepts.