[oldman]

My guess would be raccoons. Anything that has bone or fishmeal or is fertilized with fish emulsions will be interesting to them. I stopped fertilizing tomatoes when I learned that the fertilizer I used smelled like food to them. They'd dig up the plant looking for something that wasn't there. The plant would get replanted and they'd keep digging. Eventually I relocated them, but there are almays more raccoons.