I actually have no idea what makes the white covering on these trails - I can only assume pigs, urinating/marking territoty? It looks like the white markings on a clay tennis court, and is only in one area of the property, not on other pig trails. I wondered once if it was a fungus, or ducks - but I'm just assuming it has to be pigs?
Oh, interesting suggestion. There is clay in the dams, but the clay is a dark colour - I'll look closer. When I first saw the trail, I really thought it looked like a fungus.