Deer will generally cut grooves in our Rocks with their tongues. Look to see if there are any channels in yours. This will be a good indication as to whether they are hitting them.

Never tried peanut butter, but a good friend of mine swears by it. He will go but the cheap off brand, take the lid off and screw it into a tree, screw the jar back onto the lid, and then cut the bottom off the jar for access. He just went out last week and put out several jars at some of his camera sites. I'll be interested in seeing some of the pictures.