One way of looking at it, Gryph.

In some areas around here, the bull moose have become very quiet during the Rutt - mainly due to predation by wolves. When the wolves are howling every night, chasing moose, the moose become very wary of giving their location out, as answering a call would do.

Wolves also come in to bull grunts and cow bellows, and elk bugles, as do grizzlies in some areas North a bit of here, as well, just as the dinner bell of a rifle shot, can bring them in. Usually only happens when you aren't hunting griz, that is.