Mostly instictual Lizzie, it's the calls of the particular shepherd that the dog needs to learn AFAIK.
Indeed, training a sheepdog is about moulding the dog`s natural prey-drive into a herding-drive; "chase rather than kill".
Not all breeds have that herding instinct and even some Border Collies have been out-bred so far away from native working bloodlines that they can no longer be used for sheep-work.
The vocal and whistle commands we use for shepherding are added to the basic body-language and dog/handler positional cues that a young dog initially learns from it`s handler.
I can work my eldest-dog with sheep from 400 metres away; just by adjusting my body posture by simply leaning/turning (as long as she can see me)....basics she learned as a pup.; 10 years ago, are still deeply embedded in her mind even though she also now knows voice/whistle commands too.
Very clever indeed!
