Morning, Susan. It's common for me because we back up to woods. Lots of critters. However, I usually sprinkle new holes with cinnamon or ground chili pepper or garlic powder and don't have a problem. I've had them toss moth balls aside once they dig them up. Once the ground has settled and bulbs established, no problem. They are just lazy and like to take advantage of already dug dirt.
But when you back up to woods, it's nearly impossible to control all the critters. I just live with it because I love my woods!
I have a bird feeder that closes the ports when anything heavy jumps on it. The birds can feed just fine but the squirrels can't. Perhaps try one of those.
