I took some pictures at a local fun show this past weekend, and several are relevant to the topic of cryptic appaloosas like Thumper.
In the previous post I mentioned that the mottling on Thumper’s lips was what alerted me to the fact that he was not an ordinary roan. I wanted to clarify that it was the mottling paired with other clues (like his striped feet) that convinced me he was a varnish roan. Mottling on the mouth alone is not an absolute sign of the appaloosa gene. This mare has mottling, too, but she’s not an appaloosa.
She’s a fleabitten grey Arabian mare. Obviously her mottling did not come from varnish roan, since Arabians do not have the necessary gene for that.
Her mouth is mottled because she is a grey. It is not an uncommon trait among greys. In some cases, like this mare, it is pretty subtle. In this picture, taken in the shade and with front of her mouth hidden from view, her skin looks uniformly dark. Often mottling on greys is not visible in pictures. Sometimes it is nothing more than fine pink speckles around the edges of the white markings. On others it is very pronounced and involves large areas of pink skin.
This is one reason why it would be easy to hide varnish roan in a predominantly grey breed. While mottling on the mouth is usually a red flag that the appaloosa patterns might be involved, it can seem pretty routine to breeders with grey horses.