I believe you may have skunks, possums, or raccoons looking for grubs in the soil. They won't dig unless and until they find a grub, so this would be an indication that you have grubs. Try digging up a 1 square foot area around where the previous digging went on. Grubs would be within 2 inches of the surface. If you find fewer than a dozen grubs, then you don't have a grub problem - but you may still see some digging. If you find uncountable masses of grubs, then you should hit the yard with an insecticide for grubs.

I should also say that I am really anti insecticide, so please don't simply spray everything without doing the digging test first. There are a lot of beneficial insects in the soil, so you don't want to be spraying something like that willy nilly.

Thank you. Will do. I spread mily spore on the other side of the lawn and it's fine. Maybe I should do this side of the house!