That is true, they kill for the sheer joy of it sometimes.
I know dogs and cats (some, not all) kill just to kill. I know that humans kill just to kill (trophy hunters). I recently watched an on-line video where two young boys chased down a fox with snowmobiles, with a couple of older men, in the background, cheering with glee with each almost hit of the fox. Finally the fox was hit and killed.
At this point I assume that wolves must kill some for the thrill of the kill. None of this activity was observed either in the Yellowstone project or the Sawtooth (Dutcher)project. The Yellowstone project did observe “surplus killing and wounding” where wolves would be chasing elk and a small group would take a wolf in one spot while another small group of the pack would take another elk. The researchers did state that the wolves would come back later and eat the excess elk (if it hadn't been already eaten by other scavengers”.
I could easily see that wolves used to hunting elk would get into sheep and kill several because in the high adrenaline state they are in and the fact that sheep are easier to kill, they would kill more than they could eat.
I would like to here from someone who directly observed wolves killing for the joy of it.
I have been studying wolves for less than one month. For some reason, I am motivated to understand the truth (whatever that turns out to be).