Reading Barry Lopez’s book “Of Wolves and Men”:
[…] disadvantage. The important thing to bear in mind is that generally wolves do not overrun the prey population and kill it out, although they have been known to do so, just as they have, extraordinary as it seems, practiced a kind of fallow-field farming by not killing deer in certain parts of their territories for four or five years, letting the prey population recover there.



Has the scientist really asked the wolves about their intentions? :)
Or could this be a misinterpretation of some statistics?
I have learned in school that predators go for the weakest prey only. So if a herd of deer has already lost a few, then maybe there are no weak ones left in this herd, and the wolves have to suffer hunger for a while, until they find another herd.
So, another interpretation could be that the wolves simply remember the fact about the first herd, and avoid it for a while. The outcome would be the same.