On the respectable side Wolves make incrediabley efficient use of a carcass generally consuming 100%.
I hunted moose in a valley, here in the Yukon, where there were 6 fresh wolf kills in a 2 mile area (that we found, probably more) and not one had been eaten more than about 30% worth.
It seems that where prey is plentiful they do not bother to clean up, they just make another kill. There was a pack of 12 wolves working this valley and from what we could make of the sign, they were killing at least a moose a day or more. There was a bush airstrip in this valley with a fresh kill on one end one day and the next morning there was a fresh kill on the other end. Neither one more than 20% eaten, it was just wanton wholesale slaughter. I realize this "flies in the face" of general thinking but I know what I saw and it was disgusting.
To the poster that said there is no way to tell a wolf kill from a bear kill or death from natural causes, once it has been scavenged, I have to say I disagree. These were all wolf kills and were fresh, all within the week I was there. Not a single bear track on the kills or even sign of bears in the whole valley, in fact the miner working that creek said he figured the wolves ran off the 3 grizzlies that had been living there, for the past 4 years. He said that since the wolves moved in, in August he hadn't seen a bear, only the 12 wolves. I can also tell you there was nothing natural about these moose deaths, you don't have to be a forensic scientist to see they were without a shadow of a doubt wolf kills.
Unfortunately I was bowhunting and did not have a rifle or I would have thinned that pack by at least 1/2 if not every single one, if I could have.