[VRM]

Chopper,
I always enjoy reading that - thanks for the post.

It is a bit simplistic though, and certainly leaves out another major actor in the play; the shepherd.
The shepherd: provides training and food for the sheepdogs, assists them by building structures for added protection, cares for wounded/sick sheepdogs and sheep, harvests and sells/uses the products that the sheep provide.
The shepherd is not an efficient fighter like the sheepdog, but is not helpless like the sheep. The shepherd also has the responsibility to know when to move the flock if there are too many wolves or not enough grazing in the area.

Without sheepdogs the wolves would eat the sheep (and maybe the shepherd too).
Without sheep the shepherd would not be able to feed the himself or the sheepdogs.
Without the shepherd the sheepdogs would be just dogs, and the sheep would be tasty treats for dog and wolves.