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Friday inspirations 7


I have been thinking a lot about the size and spacing of spotting patterns lately. It's something I notice in appaloosa patterns and also in belton spotting. In zebras, differences in striping width are believed to come from variations in timing. The earlier the pattern starts in utero, the wider the stripes. (I made a post about this many years ago.) In appaloosa patterns, white markings on the face and legs are associated with smaller spots. This effect, sometimes called "sabino boost," can be seen in the horse above. 


A zebra hybrid was recently listed on the website Horse Bid. She has larger-than-usual spotting like many hybrid appaloosas (mules or zorses). I suspect this comes from a change in the timing in establishing the pattern, similar to the striping in zebras. 


Zappaloosa

The most helpful way to conceive of zebra striping is to imagine that, for their species, dun patterning has been amplified in the extreme. That means the stripes (dun factoring) are broader and cover more of the body than in a dun horse, and the fading of the non-factored areas (i.e., what isn’t a stripe) is diluted to white. In a zebra hybrid, all of that is toned back down so that the result looks like an ordinary horse with an overlay of somewhat darker stripes. The combination of spots so large they run together and residual striping on the body color gives Zappaloosa her unusual pattern.

 

Drea Eaglefire Sundy

Although hybrids like zorses and mules seem prone to larger spots, it is possible to find horses like this. Many horses from this foundation line of leopards have loud patterns with large spots, but this horse is an outlier in spot size even for them.

 

Lykou’s Tucson

(Tharos – Friis’ Phoebe, Theis af Virklyst)

Although this stallion only has a few spots – which is what is expected of a few-spot leopard – they are exceptionally large. He is homozygous for Lp and heterozygous for Pattern1. His sire, Tharos, has what looks like the nose-to-toes leopard version of the same type of large, widely-spaced spotting.

 

Kilimandjaro Semilly

(Action Breaker – Une Bel Marocaine, Baloubet du Rouet)

This stallion is tested as homozygous W20. One of the persistent questions about W20 has been its range; horses tested for W20 have varied dramatically in terms of how much white they show. It produces an all-white phenotype when paired with other KIT mutations (notably W5). A study of 1054 registered Paint horses showed that among the 166 horses with one copy of W20 and no other testable white pattern, 74% had enough white patterning to qualify for regular papers. That’s higher than the 70% for horses with one copy of SW2 (the splashed white pattern found in the “Gunner” line). Even so, many horses with the mutation do not have extensive white markings. Is that because the mutation needs other – perhaps currently untestable – patterning to “boost” its expression? Or are there suppression factors – also untestable – involved? Those questions make loud W20 horses like this one fascinating. It will be interesting to see what kind of patterning he produces.



Other side (which is quite different from the one linked in the title)


Broomsgrove Nerys

(Brickell Top Shot – Bryon Ways April, Snowhill Magic)

Horses like this Shire mare raise some of the same questions as the Selle Francais. Sabino phenotypes typically have a certain balance regarding the amount of white on the face and legs. When there is more white in one of those areas than the other, it is more often the face that is more extensively marked. Indeed, an imbalance between a solid or minimally marked face and high white on the legs is frequently used to identify minimal tobianos. However, it is possible to find sabino horses like this mare. Has the marking on her face been suppressed? Or is it covered by a colored patch or patches? Could it be a combination of the two? Sometimes, it is obvious, but other times, it is an open question.

Front angle shot (shows the contrast in extent of face vs. legs)


Spotilas Boesgaard

This is a different kind of change, where the spots get smaller, and the entire pattern scales down. Sheila Archer of the Appaloosa Project once referred to this as the “shrunken sweater” effect. It does look like an ordinary leopard pattern that once covered this horse shrunk between washings!



Pedigree (with more pictures)

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