intersestingly, there are two differing kinds of sheep dogs.
some like border collies, still look and act like dogs.. and the sheep are mildly frightened by them, enough so that they flock away.

there are also sheep dogs that are "wolf's in sheeps clothing's". they have long thick, wool like fur, and hide in the flock.. they are often playful, but they are at the same time large and powerful. any real wolf that came along to attach the sheep would suddenly find himself confronting a large, powerful dog.. (and not being much of a dog lover, nor very interested in breeds, i didn't go to the AKA to look up the breeds.. but we all know them, the "shepherd" dogs with long, stringy fleese like fur..
I am sure some one will supply us with a name, and links to 100 times more informations. (or at least 100 more than a non dog--no make that animal lover needs)
*Note, i don't dislike animals, it just i have never been interested in having any of my own.. not fish, not birds, not cats not dogs.. --i did sort of think about a lamb, like CK, i thought it might be a nice way to deal with the grass, and a local farm museum does exactly that.. but after reading CK's experiences with a wether.. i am cured of any romantic notions i had!