This post first appeared on July 30, 2012
My friend Steph Michaud sent some pictures from the 2012 Minnesota Horse Expo, which included the really loud chestnut leopard DREA Chief Fireagle. He is a great example of what the leopard pattern looks like on a horse without markings. Appaloosas with white on the face and legs tend to have smaller spots with wider areas of white between them. This effect is sometimes called the Sabino Boost, because the sabino patterns appear to boost the amount of white in other patterns at the expense of the colored areas. Fireagle is particularly interesting because this type of loud patterning is more often seen on appaloosas with a bay or black base color than on those that are chestnut.

But I wanted to share the pictures because Fireagle has what are sometimes called “moldy spots”. Part of what makes the leopard pattern so desirable among appaloosa breeders is that unlike the other colored areas on an appaloosa, the spots do not roan out with age. A leopard is all spots, or nearly so, so the pattern does not change significantly over time. Leopards with moldy spots are the exception in that they develop random white dots inside some of their spots. The amount seems to vary, with some spots developing pinholes of white while others appear to roan out completely.

Because this is something that develops with age, it is sometimes mistaken for greying. Appaloosas that inherit the grey gene do lose their spots, but moldy spots are not caused by greying. Greying does other things to the appaloosa patterns which is worthy of a later post, but that will require tracking down some decent pictures. This, however, seems to be some variation on the normal actions of the Leopard Complex gene.

What I have always found interesting about moldy spots is that they highlight the separate nature of the clustered spots. Loud appaloosas have large patches of color that give the impression they were made by a number of individual spots that overlapped. Because only some of the spots develop “mold”, appaloosas with this trait show that the spots really are distinct entities. They may look like one large colored patch, but as far as the body is concerned they are truly layered. (This can be seen most clearly on Fireagle’s croup, where the different spots have faded in varying degrees.)

This ties in with the upcoming post about occluding spots and badger faces, which are other instances where colored areas behave like layers in a drawing. From there I’d like to get back to the discussion on Belton patterning with some of the images that have been sent to me since the initial post on that topic. That should also put things back on track for regular postings, so stay tuned!