Walker hound is the name of one strain of the American foxhound breed. They were originally created in America in the 1700s by crossbreeding various strains of English and American hound. They are very closely related to Tree Walker Coonhounds but are technically a separate breed. They are used for many reasons which include their ability to scent, track, and hunt foxes (as well as, presumably other things like run away slaves). It is this ability which makes them useful to Uncle Buck and Mr. Hubert in the first story of Go Down Moses, "Was".

–Adrie Rappa

If we don't start him somewhere around the kitchen, we'll put the dogs on him. They'll find him if it's in the power of mortal Walker dogs to do it. (GDM 11).