A tail that is thick and covered with hair at the “root” (where it sets into the dog) for two or three inches, then tapers to a fine point at the end where the much-shorter hair looks as it’s been clipped is referred to as a “rat tail.” It’s a hallmark of the Irish Water Spaniel, but a fault in the Treeing Walker Coonhound (“Fault – having an excess of curve in tail; rat tail; excessive brush), and in the American Foxhound (“Defects-A long tail, teapot curve or inclined forward from the root. Rat tail, entire absence of brush”).

Irish Water Spaniel by Edwin Megargee (1883 -1958 )