I use a howler this time of year because coyotes are very territorial this late in the year. They are establishing thier breeding grounds right now with the most breeding activity occuring in February. Challenge calls like yips, barks, and a bark..bark...short howl will challenge their territory and makes em mad.
I have frozen cut up beaver carcasses before in large ice cream buckets and set them out......I call em Beaver Cicles. I don't have much success hunting over them though because coyotes feed mainly at night, especially over baited areas. It seems like they just know something ain't right? It's kinda like the old saying "Nothings for free" and they will wait till after dark to raid the bait stations. It will....however.....keep them in the area since they know there is available easy food nearby and that will make them come to some challenge calls easier.
If you ever have a barking, yipping coyote circle you from about 50 yards out when it's almost dark and your 15' up in a treestand......knowing that you still have to get down and walk the 1/4 mile back to the house in the dark.......you will never forget it! It's a thrill that cannot be duplicated unless you live in wolf country.