i used to guide for bears for years. If youa re using Oats don't got bigger than 1" holes in your barrel. Max of 2 of them. They will clean them out otherwise. We used to use Oats mixed with resurant grease, sugar, smoke flavor and bacon bits. It he hole was biger than 1" they cleaned it out in no time and it will cost you a pile to keep it full. Also used 20 gallon drums with a 5x 4 inch hole hung from a treebranch with a beaver in it. If it is in a tree theyhave a harder time getting the beaver out. If it is on the ground they can work it too hard.