I t works fine. I have used the old hand powered rubber varmit calls (dying rabbit)succesfully as have some friends. We always called in the winter and usually on big frozen lakes.
My brother and I once called in 9 big wolves in the Yukon along the Ashiak River. They showed up within a few minutes.
Some other friends use the howl in Feb (mating season)to call in animals. This often works after a pack has been dissturbed off a kill.