One of the reasons for the elk decline was that some geniuses put Lake Trout into Yellowstone Lake. They ate the cutthroat. Like almost all of the them. Escapements (they actually count and trap) went from 50-100K to 50-100. The Laker eradication seems to be working and successful cutthroat recovery is occurring.

But, the lack of trout in the streams forced the bears to find another protein source. Elk calves. They were very good at finding them and eating them.

An aspect the wolves brought in was fear for the elk. Instead of large herds out in the open you had small herds in the trees. This made, among other things, hunting harder. Had to hunt more, rather than scan the plains.

It is a very complex issue, made more so by politics. Most here are probably familiar with the bison/brucellosis issue amongst ranchers. Not a peep from anybody about the reservoir of brucellosis in elk, who leave the park every winter and are much more welcome (perhaps because we sell licenses and get trespass fees for hunting them?)