I think there are a lot more things you can do wrong when you try to talk the predator's language than there are when you try to imitate some smaller prey animal in distress. Have not deliberately hunted wolves, but have called coyotes for almost 30 years, and we use howlers only as a "locator" kind of call. We try to get them to howl back and then move somewhere closer so we can get them to investigate what we hope are convincing dying rabbits, ravens, magpies, crows, calves all sorts of sounds that indicate an easy meal. We have had animals come to howlers, but they always seem cautious and careful when they investigate, while full on gallops toward "food" often occur. So our howlers don't get much use.