There are more sheep than the shepherd can consume by himself, and he fears the herd will escape his control, so he allows a ~~pack~~ herd of wolfs to mingle with the flock. Only the most vicious of rams will survive. The bar for survival is being set very high. This is a pivotal evolutionary event in the bloodline of the sheep. The remaining branch will be too dangerous to be herded, and the shepherd's fears will manifest to the utmost degree.