They needed a dog with a deep chest,
short legs, and a sturdy tail: The deep chest gives the dog a place to rest his body while his
legs are throwing dirt out of the hole; the
short legs allows the Scottie to throw dirt to the sides, not back between his
legs; and, the firmly rooted, sturdy and thick tail allowed the Highlander to pull to the dog back out of the hole by the tail with the critter firmly locked in the Scottie's huge teeth and
powerful jaws.