The biggest secret to sheep herding is that it's all in the dog. There are select breeds with the innate disposition to guide sheep along their destined path. The results of a study published in the Journal of the Royal Society Interface in 2014 concluded that herding dogs are the masters of a just-as-innate two-step method.
Dogs first keep sheep bound together by weaving around side-to-side at their backs - then they simply continue guiding the sheep forward. "If the dog sees gaps between the sheep, or the gaps are getting bigger, the dog needs to bring them together," Dr. Andrew King, a scientist who worked on the study, told ABC Science.
As for why sheep seem content to just roll with the punches (or, in this case, barks)?