Good eye; it is her back. Funny thing about once I fixed this horse's problem with saddling and hooves ... I then found a trainer that encouraged me to sit very upright and dig in. Buttercup didn't like that at all. We've moved more into a lighter seat (more hunter styled) in the past months and the tail switching has calmed down some and her topline has improved because she's relaxing her back. Though, I think part of the tail switching is her "thinking." (or is that anamorphiziziziaiang -- can't spell but you catch my drift). She still is an avid tail switcher when backing, but going forward is better